2017 Microchip Technology Inc. DS00002326A-page 1 AN2326 INTRODUCTION This application note describes a driver solution for a high-torque bipolar stepper motor. The feature-rich peripherals of Microchip’s PIC16F1776/9 allows the two H-Bridge switches to control different driving tech- niques for high- and low-power stepper motor, constant or high-torque microstepping, current limiting, motor step rate setting and motor Fault event detection. The solution described in this application note has the following key features: • Control Two H-Bridge Circuits with Shoot-Through Prevention • Driving in Wave Step, Full-Step, Half-Step and Microstepping mode • Capable of Constant or High-Torque Microstep- ping Drive • Motor Current Limiting • Microcontroller Implementation of Chopper Drive • Chopper Drive Microstepping • Motor Fault Detection • Capable of Real-Time Motor Parameter Monitor- ing through Serial Communication (I 2 C, SPI, EUSART) FIGURE 1: BLOCK DIAGRAM Author: Mike Gomez Microchip Technology Inc. PIC16F1776/9 Temperature Indicator 16-Bit PWM COG1 H-Bridge Circuit Stepper Motor 1.8°/Step COG1A C5 - + C6 + - Real Time Monitoring and Controls Motor Supply Winding A ADC COG1B COG1C COG1D COG2 COG2A COG2B COG2C COG2D H-Bridge Circuit A+ A- B+ B- Winding B RSHUNT 2 16-Bit PWM TMR0 (Step Rate Generator) FIRMWARE (Full-Step, Half Step, Microstep, PWM Modulation) I 2 C (Communication) Over Temperature Detection Chopper Drive VDD VSS Current Winding Control HLT 2/4 (Stall Detection) C4 - + C3 + + Chopper Drive COG1 Auto- Shutdown Signal RSHUNT 1 Reading RSHUNT 2 Reading COG2 Auto- Shutdown Signal C1 Over Current Signal C2 Over Current Signal C2 - + C1 + - 10-Bit DAC 10-Bit DAC 10-Bit DAC 10-Bit DAC RSHUNT 1 10-Bit DAC 10-Bit DAC Winding A Stall Signal Winding B Stall Signal FVR High-Torque/High-Power Bipolar Stepper Motor Driver Using 8-bit PIC ® Microcontroller
Transcript
AN2326High-Torque/High-Power Bipolar Stepper Motor Driver Using 8-bit PIC® Microcontroller
INTRODUCTIONThis application note describes a driver solution for ahigh-torque bipolar stepper motor. The feature-richperipherals of Microchip’s PIC16F1776/9 allows thetwo H-Bridge switches to control different driving tech-niques for high- and low-power stepper motor, constantor high-torque microstepping, current limiting, motorstep rate setting and motor Fault event detection.
The solution described in this application note has thefollowing key features:
• Control Two H-Bridge Circuits with Shoot-Through Prevention
• Driving in Wave Step, Full-Step, Half-Step and Microstepping mode
• Capable of Constant or High-Torque Microstep-ping Drive
• Motor Current Limiting• Microcontroller Implementation of Chopper Drive• Chopper Drive Microstepping• Motor Fault Detection• Capable of Real-Time Motor Parameter Monitor-
ing through Serial Communication (I2C, SPI, EUSART)
FIGURE 1: BLOCK DIAGRAM
Author: Mike GomezMicrochip Technology Inc.
PIC16F1776/9
Temperature Indicator
16-Bit PWM
COG1 H-Bridge Circuit
Stepper Motor 1.8°/Step
COG1A
C5 -+ C6+ -
Real Time Monitoring
andControls
Motor Supply
Winding A
ADC
COG1B
COG1C
COG1D
COG2
COG2A
COG2B
COG2C
COG2D
H-Bridge Circuit
A+
A-
B+
B-
Winding B
RSHUNT 2
16-Bit PWM
TMR0(Step Rate Generator)
FIRMWARE (Full-Step, Half Step, Microstep,
PWM Modulation)
I2C(Communication)
Over Temperature Detection
ChopperDrive
VDD
VSS
Current Winding Control
HLT 2/4 (Stall Detection)
C4 -+C3+ +
ChopperDrive
COG1 Auto- Shutdown Signal
RSH
UN
T 1
Rea
ding
RSH
UN
T 2
Rea
ding
COG2 Auto- Shutdown Signal
C1Over Current
Signal
C2Over Current
Signal
C2 -+C1+ -
10-Bit
DA
C
10-Bit
DA
C
10-Bit
DA
C
10-Bit
DA
C
RSHUNT 1
10-Bit
DA
C
10-Bit
DA
C
Winding A Stall Signal
Winding BStall Signal
FVR
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Figure 1 shows the block diagram of a High-Torque/High-Power Bipolar Stepper Motor Driver based on thePIC16F1776/9 microcontroller. The motor driverutilizes different Core Independent Peripherals (CIP) inthe microcontroller to perform complete stepper motordrive with minimum intervention from its CPU. Theseare the CIPs used in the design:
The novelty of this solution is the way CIPs arecombined with other on-chip peripherals such as I/Oports, Analog-to-Digital Converter (ADC), FixedVoltage Reference (FVR), Digital-to-Analog Converter(DAC) and Timers.
These peripherals are internally connected byfirmware, significantly reducing the number of externalpins required for the implementation. For the detailedschematic diagram, refer to Appendix A: “CircuitSchematic”.
CONTROLLING THE STEPPER MOTORA stepper motor distinguishes itself from other motorsby its ability to move in a discrete number of angularincrements or steps. It is a digital version of an electric
motor that divides a full rotation into a number of equalsteps and moves one step at a time. It can be easilyconfigured to move some specific number of steps aswell as to create a precise Stop command. Dependingon the application’s speed and torque requirements,stepper motor usage varies from low up to high-powerprecision control applications. To know more about thebasics and fundamentals of stepper motors refer toAN907, “Stepper Motors Fundamentals”.
Drive Circuit and Control MechanismTo make the rotor spin, a rotating magnetic field mustbe generated. The two stepper motor windings(Winding A and B) are electrically energized to createa rotating field and a varying magnetic pole polarity onthe stator (North and South) through the use of the H-Bridge circuit with the Complementary OutputGenerator (COG) as the control signal. Figure 2illustrates the current flow through the H-bridge circuit.The current will flow from left to right in Winding A whenMOSFETs Q1 and Q4 are turned ON while Q2 and Q3are OFF. On the other hand, the current will flow fromright to left when Q2 and Q3 are ON while Q1 and Q4are OFF. The same principle applies with theMOSFETs Q5, Q6, Q7 and Q8 on Winding B. Theturning ON and OFF of the MOSFETs is implementedthrough the use of the COG Forward and Reverse Full-Bridge mode output as a control signal. Refer toTB3119, “Complimentary Output Generator TechnicalBrief” for more information regarding the COGperipheral of PIC® microcontrollers.
FIGURE 2: COG AND H-BRIDGE CIRCUIT STEPPING ALGORITHM
COG1A COG1C
COG1B COG1D
Q1 Q3
Q2 Q4
FORWARD MODE REVERSE MODEQ1/Q5 ON OFFQ2/Q6 OFF MODULATEDQ3/Q7 OFF ONQ4/Q8 MODULATED OFF
A A’Winding A
COG2A COG2C
COG2B COG2D
Q5 Q7
Q6 Q8
B B’Winding B
FORWARD MODE REVERSE MODE
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Due to the constantly alternating flow of current, oneinherent danger that should be monitored in using anH-Bridge circuit is the occurrence of a crossconduction. Cross conduction is a condition where thehigh- and low-side MOSFETs are both switched ON atthe same time. This scenario will cause a shoot-through current, which could damage the driver’scomponents. Using the COG’s Counter registers, adead-band delay can be imposed on the COG outputs.
This provides non-overlapping output signals that willprevent shoot-through. The COG contains two 6-bitdead-band delay counters, one for the rising edge ofthe input source and the other for the falling edge of theinput source. This dead-band delay is timed bycounting COG clock periods from zero up to thespecified value in the two COG Counter registers(COG1DBR and COG1DBF). Figure 3 illustrates theCOG outputs with dead-band delay.
FIGURE 3: COG OUTPUT DEAD-BAND TIMER
To continuously step the stepper motor to its desiredposition, the excitation on the stator windings must besequenced in a specific sequence. Figure 4 illustratesthe basic block diagram in driving the windings of abipolar stepper motor. A Timer0 (TMR0) peripheral isused to provide the time interval between changes ofsteps throughout the excitation sequence. There aredifferent stepping sequences or algorithms that can beimplemented on a stepper motor. The choice of whichalgorithm to use depends primarily on the application’srequirements for motor operational speed, torque andstep resolution. A detailed explanation of the differentstepping algorithms will be given in the next Section“Step Mode Implementation”. The motor steppingrate and the rotation is implemented using theComplementary Output Generator (COG). The COGproduces multiple output complementary signals,suitable to drive a Full-Bridge or H-Bridge circuit.
COG1A/2A
COG1B/2B
COG1C/2C
COG1D/2D
Rising Event Dead-band
Falling Event Dead-
band
Rising Event Dead-band Falling Event Dead-band
COG1A/2A
COG1B/2B
COG1C/2C
COG1D/2D
Rising Event Dead-band Time (sec) =
COGxDBR = 0x0C
625 nS
1COG_clock
x COGxDBR
Falling Event Dead-band Time (sec) =
COGxDBF = 0x0C
625 nS
1COG_clockx COGxD
BF
COG1A/2A
COG1B/2B
COG1C/2C
COG1D/2D
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FIGURE 4: STEPPER MOTOR DRIVE CIRCUIT
STEPPER MOTOR CHARACTERISTICSTo ensure the motor’s optimal performance, differentmotor characteristics such as torque, speed, andstepping rate must be considered. This chapterdiscusses these characteristics and how they influencethe final implementation.
Torque GenerationThe first thing to understand in designing a steppermotor drive is how the torque is generated. A torque isdeveloped when the magnetic fluxes of the rotor andstator are displaced relative to each other. When thewinding is being energized with current, a magnetic fluxis developed in the stator. Due to the high magneticpermeability of the material in the stator, the developedmagnetic flux is confined and creates a strong fluxconcentration on the stator pole. This magnetic fluxcauses the rotor to be attracted and eventually rotatetowards the energized stator. Motor torque can begenerated by forcing the motor shaft out of its stableposition. It can be done by either manually twisting theshaft or by electrically driving the motor to step to a newposition, and the amount of torque produced dependson factors such as motor stepping rate, winding drivecurrent and the drive design.
Stepping RateMotor stepping rate is the number of steps throughwhich the shaft rotates during a specific time intervaland is commonly referred to as PPS (Pulse perSecond). It dictates the running speed of a motor.Example 1 shows the sample calculation for the motorstepping rate.
In a 1.8° step resolution motor, a rotational velocity of120RPM can be generated by applying a 400PPS steprate using a Full-Step mode or an 800PPS step rateusing a Half-Step mode. In the case of Microsteppingmode the calculated step count should be divided by 1/4, 1/8 or 1/16 depending on the microstep resolutionbefore calculating for the step rate in order to retain thesame speed calculation as the full step. The calculatedPPS will then be used by the TMR0 peripheral as areference in producing the drive pulse for the motorwinding. More detailed information on how the PPS istranslated into the necessary driving pulse can befound on the Section “Step Mode Implementation”.
16 Bit PWM
COG1 H-Bridge Circuit
COG1A
COG1B
COG1C
COG1D
COG2
COG2A
COG2B
COG2C
COG2D
H-Bridge Circuit
A+
A-
B+
B-16 Bit PWM
TMR0(Step Rate Generator)
FIRMWARE(Stepping Algorithm)
Cha
nge
in C
OG
Mod
e S
igna
l
Current Modulation
Current Modulation
MotorWinding A
MotorWinding B
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EXAMPLE 1: STEPPING RATE CALCULATION
It is also important to understand that the stepping rateaffects the amount of motor torque generated. A higherstepping rate will result in a lower torque output. Insolving motor torque limitation at higher speed, thecurrent limiting technique can be implemented on thedesign. More detailed information about the currentlimiting technique implementation can be found in theSection “Current Limiting”.
STEP MODE IMPLEMENTATIONStep mode refers to the method or technique ofstepping the motor each time the polarity of the currentin the stator winding changes. It is simply a method ofrotating a stepper motor. Depending on the requiredapplication, different step modes can be implementedto vary motor output resolution and torque. Thefollowing are the step modes that can be implementedon the PIC16F177X microcontroller:
Wave DriveIn wave drive mode, the stepper motor is driven byenergizing only one winding at a time. Figure 5 showsthe implementation of wave drive and its correspondingstepping algorithm.
Step Count(Steps per Revolution)
360°
Step Angle Degree (°)
360°
1.8°200 steps/rev= = =
Timer0(time needed at every step
for Full Step)
1
400 PPS= 2.5mS=
Timer0(time needed at every step
for Half Step)
1
800 PPS= 1.25mS=
400PPS is the needed Stepping Rate to attain a 120RPM in a Full Step Mode Configuration
Stepping Rate(Pulse per Second PPS)
Desired RPM
60 secsx Step Count
400PPS120 RPM
60 secsx 200 steps/rev
=
= =
Full Step Mode Stepping Rate
800PPS is the needed Stepping Rate to attain a 120RPM in a Half Step Mode Configuration
Stepping Rate(Pulse per Second PPS)
Desired RPM
60 secsx Step Count
800PPS120 RPM
60 secsx (200 steps/rev ÷ ½)
=
= =
Half Step Mode Stepping Rate
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FIGURE 5: WAVE DRIVE IMPLEMENTATION
In Figure 5, both Winding A and Winding B areconnected to the H-Bridge drive circuit which isconnected to the COG peripheral of a PIC MCU. Step1 on the algorithm table applies a positive voltage orlogic High to winding lead A while driving the windinglead A’ low, and the current is generated in the directionas shown in Figure 5 creating a magnetic north andsouth on the stator poles accordingly and a rotationtowards the next stator pole. On Step 2, the voltageapplied in winding lead A is removed and put on the
winding lead B. The winding lead B is driven high whilewinding lead B’ is driven low, again creating a rotationtowards the next stator pole. The process will continueup to Step 4 then repeating the cycle. Notice that thewave drive is done by turning ON one winding at a time.This is why it is also referred to as a One-Phase ONvoltage sequence. The term wave is derived due to thegenerated voltage sequence that resembles a wave.Figure 6 shows the generated voltage drive sequenceon the motor windings.
FIGURE 6: WAVE DRIVE WINDING VOLTAGE SEQUENCE
This stepping algorithm can be easily implementedthrough the use of a COG peripheral. As discussed inthe Section “Drive Circuit and ControlMechanism”, this peripheral is used to drive theMOSFETs, which in turn drive the corresponding motorwindings. The COG mode is toggled from Forward toReverse mode, as dictated by the stepping algorithm.The rate at which the mode is toggled depends mainlyon the desired stepping rate (Refer to Section“Stepping Rate” for the calculation). The pre-calculated value of the stepping rate is loaded into the
TMR0 register that interrupts the CPU at theappropriate time intervals to perform the subsequentsteps. Figure 7 shows the step implementation of wavedrive and Figure 8 shows its software implementation.
One advantage of this method is that it has the simplestdrive implementation, while the disadvantage isreduced torque output performance. Since thewindings are energized one at a time, only half of theoverall motor torque can be used. More degradation oftorque performance can be observed with this methodwhen using a unipolar motor construction because ofits multiple winding constructions.
Full-Step DriveOn a full-step drive, two phases are always energized.Both Winding A and Winding B are energizedsimultaneously to rotate the motor. Figure 9 shows theimplementation of full-step drive and its correspondingstepping algorithm.
In Figure 9, two windings are connected to a motordrive circuit which is connected to the COG peripheralof a PIC MCU. Step 1 of the algorithm table applies apositive voltage or logic High to both winding leads Aand B while driving the winding leads A’ and B’ low.Notice that when both Windings A and B are energized,it creates the same polarity on adjacent poles whichresults in the rotor being equally attracted by both polesand lining up directly in or with the middle as opposedto being lined up with a specific stator pole as seen inthe wave drive. Step 2 in the algorithm maintains the
current flow direction in Winding B while reversing thecurrent direction in Winding A. This causes the rotor torotate 90 degrees and lie in between the next two statorpoles. Continuing the algorithm up to Step 4 producesa complete motor rotation. Since it energizes bothwindings at the same time, a full-step drive is alsoreferred as a Two-Phase ON voltage sequence.Figure 10 shows the voltage drive sequence on themotor windings. The voltage sequence of full-step driveclearly demonstrates that at any given time the currentis flowing through both windings.
FIGURE 10: FULL-STEP DRIVE VOLTAGE SEQUENCE
Just like the wave drive, the full stepping algorithm canbe easily implemented through the use of COGperipheral’s Forward and Reverse Full-Bridge mode.Figure 11 shows the step implementation of full-stepdrive and Figure 12 shows its software implementation.
Compared with the wave drive method, the advantageof this method is an increased output. Since twowindings are energized at the same time, greatertorque can be produced using the full step whilemaintaining the same amount of step angle orresolution.
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In Figure 13, the single-step response characteristicvs. time of a wave and full-step drive is illustrated. Thestep time “t1” is the time it takes the motor shaft torotate one step angle once the first step pulse isapplied. This step time is dependent on the ratio oftorque and the applied load on the motor. Since thetorque is a function of the displacement it follows whatthe acceleration will also be. Therefore, when movingin large step increments such as in Wave or Full-Drivemode a high torque is developed and consequently ahigh acceleration. This can cause overshoots and ring-ing on the motor. The settling time T1 is the time it takesthese oscillations or ringing to cease. Subsequentsteps such as t2 to T2 will also suffer from the sameringing and oscillation. In severe cases, this ringingcould be so pronounced that the rotor will not have timeto settle before the next step pulse is applied.
In certain applications where the motor is operated at alower speed, the resonance phenomenon can beundesirable. To eliminate such behavior, other steppingalgorithms such as half-step and microstepping drivecan be implemented.
Half-Step DriveHalf-step drive is an algorithm that is derived bycombining both wave and full-step drive techniques. Itis a drive technique that increases the motor resolutionby reducing the motor’s default stepping angle by half.For example, a 90° per step motor will have a new stepangle of 45° when half-step drive is used. Since therotor shaft travels less distance in a 45° step comparedto the original 90° step, the ringing produced at eachstep is minimized, thereby reducing the resonanceeffects. Figure 14 shows the implementation of half-step drive and its corresponding stepping algorithm.
FIGURE 14: HALF-STEP DRIVE IMPLEMENTATION
H-Bridge
H-Bridge
COG2
COG1
H-Bridge
H-Bridge
COG2
COG1
H-Bridge
H-Bridge
COG2
COG1
H-Bridge
H-Bridge
COG2
COG1
STEP 1 STEP 2
STEP 3 STEP 4
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In Figure 14, no significant changes from wave and full-step drive can be observed in the motor connection andimplementation. However, the step algorithm is nowtwice as long as in the wave or full-step drive. Thismakes sense considering that reducing the step angleby half will take twice as many steps to complete a 360degree rotation. The first step used in the algorithm isactually the first step of the wave drive in which currentflow occurs only in the Winding A and the rotorresponds by aligning itself with the stator poles.Likewise, the second step used is the first step of thefull-step drive in which the Winding A and Winding Bare energized at the same time, resulting the rotor toposition itself between stator poles. The drive algorithmof wave and full-step are alternately used in the Half-Step mode to generate the eight-step algorithm.Figure 15 shows the actual winding voltage sequenceproduced on the motor windings.
FIGURE 15: HALF-STEP DRIVE VOLTAGE SEQUENCE
The same as the wave and Full-Step mode, the half-step algorithm can be implemented easily by using theCOG peripheral. Figure 16 shows the stepimplementation of half-step drive and Figure 17 showsits software implementation.
When using the half-step algorithm there are someimportant additional considerations. Motor speed willbe reduced to half the speed of the Full-Step mode.This means that the stepping rate should be doubled toretain the same amount of speed. Also, since half thetime only one winding is energized, torque will bedramatically reduced in Half-Stepping mode.
MicrosteppingMicrostepping is a way of moving the stator flux of astepper motor smoothly compared to the Wave, Fulland Half-Step Drive modes. It offers an increase inoverall system performance by further reducing themotor’s resonance problem in exchange for moreprocessing power and a more complex controlalgorithm. The results are a significant reduction inmotor vibration and stepping noises at lower speedwhile at the same time producing a much higher
resolution and smaller step angles. Microsteppingworks on the principle of gradually increasing anddecreasing the current in each winding. The currents inthe windings are continuously varied to break up onefull step into many small discrete steps. For example,using a basic Full-Step mode, one electrical cyclealways consists of four full steps. Hence, one full stepof any stepper motor with any value of step anglecorresponds to 360/4 or 90 degrees of electrical angle.If the 90° electrical cycle is further subdivided into muchsmaller steps, normally in multiples of 8, 16, 32 or 64, itis referred to as a microstepping drive. This techniqueof subdividing steps is achieved by pulse-widthmodulating the voltage driving the motor windingsinstead of being turned on and off abruptly. There aremany different microstepping modes available, withstep lengths from ¼ full-step down to 1/64 full-step.This means that a stepper motor with 90° step anglewill have a new step angle of 22.5° at ¼ microstepping
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and 1.4° at 1/64 microstepping. Aside from the differentmicrostepping modes, microstepping can also beclassified according to its torque output. It can beclassified as either a high-torque or a constant-torquemicrostepping. The next section will explain theworking principle of the different modes and types ofmicrostepping and how to implement it in PICmicrocontrollers.
High-Torque MicrosteppingAs indicated by the name, high-torque microsteppingmaximizes the torque production on the stepper motor.It creates a microstepping by alternately varying thecurrent in the two windings of a stepper motor. A briefdescription of what is happening is that one winding ispowered while the current in the other winding isgradually dropped to zero, reversed, and then rampedup again. This sequence is then repeated for the otherwinding. Implementation of high-torque microsteppingcan be easily understood by comparing the phasediagram and the corresponding torque diagram of afull-step drive and high-torque ¼ microstepping inFigure 18.
FIGURE 18: PHASE DIAGRAM AND TORQUE CURVE RESPONSE
Figure 18 (A) and Figure 18 (B) represent the phasecurrent diagram of a Full-Step Drive mode and high-torque ¼ microstepping, respectively. In a phasecurrent diagram, phase currents are analyzed byplotting the current of Winding A (Ia) vs. the current ofWinding B (Ib). Both stepping algorithms in the diagramare arranged in counter-clockwise rotation starting fromthe point on the upper right corner. On the full-stepdrive (A), the first step is achieved by completely
turning ON both Winding A and Winding B as denotedby the coordinates of the point Step 1 which is (100%Ia, 100% Ib). On Step 2, it is achieved by completelyturning on both Winding A’ and Winding B. Note that thepoints lie on the Quadrant II of the phase diagram withcoordinates of (-100%Ia, 100%Ib) which means thatthe opposite leads of Winding A (Winding A’) need to beenergized. Continuing the diagram to the 4th step, itcan be noticed that the phase current diagram followed
-100
-80
-60
-40
-20
20
40
60
80
100
20 40 60 80 100-100 -80 -60 -40 -20IA (%)
IB (%)
(A) Phase Diagram and Torque Response of Full Step Drive
-100
-80
-60
-40
-20
20
40
60
80
100
20 40 60 80 100-100 -80 -60 -40 -20
(B) Phase Diagram and Torque Response of High Torque ¼ Microstepping
STEP 1
O
(100% IA, 100%IB)
STEP 4(100% IA, -100%IB)
STEP 2(-100% IA, 100%IB)
STEP 3(-100% IA, -100%IB)
STEP 1(-41% IA, 100%IB)
STEP 2( -100% IA, 100%IB)
STEP 3100% IA, 41%IB)
IA (%)
IB (%)
Step 2(-100% IA)
Step 10(100% IA)
Step 2(100% IB)
Winding ATorque
Winding BTorque
Step 14 (100% IB)
Step 14 (100% IA)
Step 2 (-100% IA)
Step 2 (100% IB)
Step 6 (-100% IB)
Step 6 (-100% IB)
Step 10 (-100% IB)
Step 10 (100% IA)
Step 14 (100% IA)
Step 2 (-100% IB)
Step 14 (100% IB)
Winding ATorque
Winding BTorque
Step 1(100% IA)
Step 1(100% IB)
Step 2(-100% IA)
Step 2(100% IB)
Step 3(-100% IA)
Step 3(-100% IB)
Step 4(100% IA)
Step 4(-100% IB)
STEP 16(0% IA, 100%IB) STEP 15
(41% IA, 100%IB)STEP 14
(100% IA, 100%IB)
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the same driving algorithm as the full-step drive tablediscussed in the previous chapter. Now looking on theFigure 18 (B), the resolution from the previous isincreased by adding more points or steps on thediagram. The coordinate of the added step points canbe identified by creating a plot from the center point(0%IA, 0%IB) extending up to the square path line witha Ɵ equal to the mode step angle. For example, thetotal step points for ¼ microstepping is 16, this resultsto the Ɵ or step angle of the ¼ microstepping to be22.5°. Extending an arm or ray going to the square pathwill lead to Step 1 coordinates of (-41% IA, 100% IB),Step 2 coordinates of (-100% IA, 100%) and the lastStep 16 with coordinates of (0% IA, 100% IB).
The torque output on the diagram is denoted by thelength or distance of the center from the step points.Therefore, the maximum torque possible can beachieved on Step 2, 6, 10 and 14, as shown in thetorque response in Figure 18. This is true because theWinding A and B on the following steps are completelyturned ON. It can also be noticed that the high-torquesteps are located on the four corners of the diagram. Byconnecting all the points together, a square phasediagram can be seen. This is the reason why high-torque microstepping is also referred to as the squarepath microstepping.
Due to the varying production of torque per steps of thehigh-torque microstepping, this method tends to be abit choppy and produces some vibrations. To overcomethis problem, another form of microstepping isintroduced which is the constant-torque microstepping.
Constant-Torque MicrosteppingConstant-torque microstepping is used to produce aconstant torque all throughout the stepping algorithm. Itproduces less torque compared to high-torquemicrostepping but produces a smoother, less noisy andless vibration stepping drive. It creates a microsteppingby simultaneously varying the current in both windingsof a stepper motor compared to just alternately varyingthe winding current in the high-torque microstepping.
The torque curve produced by both Winding A andWinding B of the constant current microstepping can beexpressed mathematically by Equation 1 andEquation 2, respectively.
EQUATION 1: WINDING TORQUE
To successfully implement a constant-torquemicrostepping, a technique referred to as sine-cosinemicrostepping is used to adjust the current in eachwinding so the net torque produced will be constant. Ingeneral, the torque produced by each winding isproportional with the current in that winding and thetorques add linearly. Therefore, if we want to hold orstep the motor at any angle θ of the microstepping, itcan be done by setting the currents through the motorwindings to the values given in Equation 2.
EQUATION 2: WINDING CURRENT
With the given Equation 2, the resultant stator currentis the vector sum of the individual winding currentsrepresented by Equation 3 This only shows that at anyangle θ, the resultant current remains the same andequal to IMAX, producing a constant-torque output forthe motor.
EQUATION 3: RESULTANT STATOR CURRENT
To further understand the implementation of theconstant current microstepping, Figure 19 shows thephase diagram of both wave drive and the ¼ constant-torque drive algorithm.
TA H sin=
TB H cos=
Where:
TA = Winding A Torque
TB = Winding B Torque
H = Motor Holding Torque
Angle in electrical degrees from a full stepposition
IA IMAX sin=
IB IMAX cos=
IMAX sin 2 IMAX cos
2+=
IMAX 2sin 2cos+ =
IMAX electrical degree=
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FIGURE 19: PHASE DIAGRAM AND TORQUE CURVE RESPONSE
Figure 19 (A) and Figure 19 (B) represents the phasecurrent diagram of a Wave Drive mode and constant-torque ¼ microstepping, respectively. On the wavedrive (A), the first step is achieved by driving thewinding lead A high while winding lead A’ is low andwinding lead B/B’ is turned off, as denoted by thecoordinates of the point Step 1 which is (100% Ia, 0%Ib). On the other hand, Step 2 is achieved by driving thewinding lead B high while winding lead B’ is low andwinding lead A/A’ is turned OFF. Continuing thediagram until the 4th step, it can be noticed that thewindings are energized the same as the Wave Drivemode discussed in the previous chapter. Now lookingat Figure 19 (B), the resolution from the previous isincreased by adding more points or steps to the
diagram. The coordinates of the added step points canbe identified by using Equation 4 and Equation 5 formotor current Ia and Ib, respectively. For example,assume that the IMAX value is one and the drive is instep number one. The sin of 360° multiplied by thepresent step number divided by 16 (¼ microsteppingresolution) will result to .38. This means that themodulation for Winding A at Step 1 should be only 38%of the maximum current. When the calculation iscontinued up to Step 16 and the result is plotted on thephase diagram, it can be noticed that a circle path isproduced by connecting all the step points. This is thereason why constant-torque microstepping is alsoreferred to as the circle path microstepping.
EQUATION 4: WINDING A CURRENT FORMULA FOR MICROSTEPPING
-100
-80
-60
-40
-20
20
40
60
80
100
20 40 60 80 100-100 -80 -60 -40 -20
(A) Phase Diagram and Torque Response of Wave Drive
(B) Phase Diagram and Torque Response of Constant Torque ¼ Microstepping
STEP 1(100% IA, 0%IB)
IA (%)
STEP 4(0% IA, -100%IB)
STEP 3(-100% IA, 0%IB)
STEP 2(0% IA, 100%IB)
IB (%)
A
B
STEP 4 STEP 1 STEP 2 STEP 3 STEP 4
A’
B’
Winding ATorque
Winding BTorque
-100
-80
-60
-40
-20
20
40
60
80
100
20 40 60 80 100-100 -80 -60 -40 -20IA (%)
STEP 1(-38% IA, 92%IB)
IB (%)
STEP 2(-71% IA, 71%IB)
STEP 3(-92% IA, 38%IB)
STEP 16(0% IA, 100%IB )
STEP 4(-100% IA, 0%IB)
Step 12 (0% IB)
Step 16 (100% IB)
Step 4 (0% IB)
Step 4(-100% IA)
Step 8 (0% IA) Step 16
(0% IA)
Step 8 (-100% IB)
Step 8 (0% IA)
Step 12 (-100% IA)
Step 12 ( 0% IB)
Step 12 (0% IB)
Winding ATorque
Winding BTorque
Step 8 (-100% IB)
Step 12 (100% IA)
Step 12 (100% IA)
Step 16 (0% IA)
Step 16 (100% IB)
IA IMAX Step Number 360 Step Resolution sin=
2017 Microchip Technology Inc. DS00002326A-page 17
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EQUATION 5: WINDING B CURRENT FORMULA FOR MICROSTEPPING
Microstepping ImplementationThe next question is how to drive calculated variablecurrents through the coil and how to implement it usingPIC microcontrollers. There are different ways toachieve this, but the best way is:
1. Use the Core independent COG peripheralavailable on PIC microcontrollers to easily drivethe H-Bridge circuit.
2. Apply the PWM peripheral as the input sourcefor the COG to be used for the currentmodulation on the motor windings.
3. Create a timer interrupt that will be triggered forevery step on the algorithm.
Figure 20 and Figure 21 show the COG drive signal forhigh- and constant-torque microstepping, respectively.
FIGURE 20: HIGH-TORQUE MICROSTEPPING COG DRIVE SIGNAL
DS00002326A-page 18 2017 Microchip Technology Inc.
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FIGURE 21: CONSTANT-TORQUE MICROSTEPPING COG DRIVE SIGNAL
Microstepping PerformanceFigure 22 and Figure 23 shows the actual motorperformance when the high-torque and constant-torque microstepping is applied.
FIGURE 22: HIGH-TORQUE ¼ MICROSTEPPING
Q1COG1A
Q2COG1B
Q3COG1C
Q4COG1D
Q5 COG2A
Q6 COG2B
Q7 COG2C
Q8COG2D
Win
ding
A
COG Drive
STEP 1 STEP 2 STEP 3 STEP 4 STEP 5 STEP 6 STEP 7
ForwardModulated
ForwardModulated OFFForward
ModulatedReverseModulated
ReverseModulated ReverseReverse
Modulated
Win
ding
B
COG Drive ForwardModulated
ForwardModulated ForwardForward
ModulatedForwardModulated
ForwardModulated OFFForward
Modulated
STEP 8 STEP 9 STEP 10
ReverseModulated
ReverseModulated
ReverseModulated
ReverseModulated
STEP 11 STEP 12
Reverse
OFF
STEP 13 STEP 14
ReverseModulated
ForwardModulated
STEP 15 STEP 16
OFF
Forward
ReverseModulated
ReverseModulated
ReverseModulated
ReverseModulated
ForwardModulated
ForwardModulated
Winding ACurrent
Winding BCurrent
Winding AVoltage
Winding BVoltage
2017 Microchip Technology Inc. DS00002326A-page 19
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FIGURE 23: CONSTANT-TORQUE ¼ MICROSTEPPING
CURRENT LIMITINGStepper motors are often run at voltages higher thantheir rated voltage, specifically on applications that usea high-torque stepper motor. Although this is notnecessarily the case for very small stepper motors,
high-torque stepper motors need to run at highervoltages in order for the motor to reach its full potential.The higher the voltage applied, the greater the torque amotor can produce but the more it will affect thebehavior of the current on the windings. Figure 24shows the behavior of the current on a stepper motor.
FIGURE 24: CURRENT WAVEFORM ON AN INDUCTIVE-REACTIVE CIRCUIT
Winding ACurrent
Winding BCurrent
Winding AVoltage
Winding BVoltage
63%
63%
IMAX = V/R
Time
Cur
rent
t = 0 e e
t = t1e = L/R
dI/dt (0) = V/L
V
t = t1
+ R
L
Inductive-Reactive Circuit
DS00002326A-page 20 2017 Microchip Technology Inc.
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A stepper motor can be modeled as an inductivereactive circuit. Due to its composition of several coilsof copper wire, its two inherited physical properties areresistance and inductance. The resistance is the oneresponsible for some of the motor‘s power loss whilethe inductance makes the motor winding opposecurrent changes, and therefore limits high-speedoperation. Referring to Figure 24, when a supplyvoltage is connected to the winding, the current risesaccording to Equation 6. Initially the current increasesat a rate according to Equation 7. The rise rate willdecrease as the current approaches its maximum levelas denoted by Equation 8. On the other hand, when asupply voltage is disconnected at t = t1, the current willstart to decrease according to Equation 9.
EQUATION 6: INSTANTANEOUS CURRENT IN RL CIRCUIT
EQUATION 7: RL CIRCUIT CURRENT RISE RATE
EQUATION 8: CURRENT RISE RATE AT MAXIMUM CURRENT LEVEL
EQUATION 9: INSTANTANEOUS CURRENT DECAY
This behavior of the current is acceptable on low speedand low stepping rate motor application. The problemcomes when a higher motor speed operation isnecessary. When a square wave voltage is applied tothe winding, which is the case in Wave, Full and Half-Step Drive mode, the current will be decreased andsmoothed. Figure 25 shows current waveformbehavior at three different motor stepping rates.
FIGURE 25: CURRENT WAVEFORM AT DIFFERENT STEPPING FREQUENCY
Above a certain stepping rate frequency (B) (C) thetotal motor current never reaches its maximum value.As the torque of the motor is approximatelyproportional to the current, the maximum producedtorque will be reduced as the stepping rate frequencyincreases. Also, when the stepping rate is further
increased, the motor has now a tendency to be stalledand missed steps due to the lack of current that willdrive the motor windings.
To overcome the effect of stepping rate and inductanceto the motor current and also to gain a high-torqueresponse at a higher stepping rate, one solution will bedriving the motor at the maximum voltage possible.
I t V R 1 e t R L–– =
I t O V L=
IMAX V R=
I t V R et t1– R L–
=
Period
Period
Period
Time
Time
Time(A)
(B)
(C)
IMAX
-IMAX
IMAX
-IMAX
IMAX
-IMAX
Current
2017 Microchip Technology Inc. DS00002326A-page 21
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Driving the motor with a higher voltage will force morecurrent on the windings as well as increase the rise rateof the current, as denoted when increasing the value ofvoltage (V) in Equation 6. Although it is a good solution,it is important to take into consideration that exceedingthe maximum specified voltage and current will result ina decrease in motor lifetime and damage the drive cir-cuitry. A solution to avoid this scenario is to implementa chopper driver circuit. The chopper drive will be usedto limit and control the current while feeding the motorwith a higher voltage. The next section will discuss howa chopper drive can be implemented using the PIC®
microcontroller peripherals.
Chopper DriveThe chopper driver provides an optimal solution forcurrent control on motor winding. The basic ideabehind the chopper control is to use a high-voltagesource to bring the current in the winding of a steppingmotor up to IMAX very quickly then when IMAX isreached, the voltage is chopped or switched off tomaintain its rated voltage and current rating. Figure 26illustrates the implementation of the chopper driveusing a PIC microcontroller.
FIGURE 26: PIC MICROCONTROLLER IMPLEMENTATION OF CHOPPER DRIVE
Chopper drive is done by sensing the peak current onthe motor windings via a shunt resistor (RSHUNT)connected in series with the motor. As the currentincreases, a voltage develops across the RSHUNT,which is used as an input to the comparator. When thepredetermined reference level defined by the FVR andDAC voltage output (VDAC_Reference) is reached, thecomparator triggers an Auto-shutdown command onthe COG peripheral. As the COG completely turns off,the current will then decay until the RSHUNT voltage isbelow the VDAC_Reference and then triggers an Auto-restart command on the COG, which turns back ON theCOG peripheral.
The comparator used is provided with hysteresis sothat the voltage is not reapplied until the VRSHUNT =VDAC_Reference – VCHYSTERISIS. Hysteresis isnecessary to prevent limiting the frequency with which
the comparator and MOSFET chop the supply voltage.Figure 27 and Figure 28 show the drive waveform andthe actual resulting waveform in a chopper driverimplementation, respectively.
FVR
C1
C2
16Bit-DACR
SHU
NT
1
RSH
UN
T 2
H-Bridge B H-Bridge A
COG1
COG2 Shutdown Signal
Shutdown Signal
VDAC_Reference
VRSHUNT2
VDAC_Reference
VRSHUNT1
+
+
-
-
DS00002326A-page 22 2017 Microchip Technology Inc.
AN2326
FIGURE 27: CHOPPER DRIVE CURRENT WAVEFORM
FIGURE 28: CHOPPER DRIVE CURRENT AND VOLTAGE RESPONSE
Time
Time
VDAC_Reference
VCHYSTER
ISUPP
LYIM
OTO
R
Chopper Generated ON/OFF Pulse on COG
Time
(A). Motor Voltage and Current Response at 100RPM(Without the Chopper Drive Implementation)
(B). Motor Voltage and Current Response at 150RPM(Without the Chopper Drive Implementation)
(C). Motor Voltage and Current Response at 150RPM(With Chopper Drive Implementation)
2017 Microchip Technology Inc. DS00002326A-page 23
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Chopper Drive MicrosteppingAside from its current limiting function, the chopperdrive can also be used to implement a microsteppingtechnique on a stepper motor. From the previousdiscussion, microstepping varies the currentsinusoidally between 0 and IMAX rather than bringingthe current up to IMAX as quickly as possible, resultingin a reduction of motor resonance and generatinghigher resolution steps. By combining thecharacteristics of microstepping drive and high-voltagechopper drive, a motor driver that allows a high-power/torque motor to operate at the highest speed possiblewhile gaining an increase in the overall motorperformance can be created.
Figure 29 shows the implementation circuit for chopperdrive microstepping. In chopper drive microstepping,the winding current is being monitored and controlled
instead of the winding voltage. The winding current isdirectly proportional and in phase with the producedtorque while the winding voltage is out of phase with theproduced torque. As a result, controlling the currentprovides the best performance in driving the motor.Chopper drive microstepping can be implemented bycreating a dynamic VDAC_Reference voltage set pointthat resembles a digitized sine and cosine waveform.The available high resolution DACs on PIC16F1776/9are used as a reference for Comparator 1 andComparator 2. Using a digitized sine wave referenceon the RSHUNT1 and a digitized cosine wavereference on the RSHUNT2 allows the driver toproduce a voltage level that shows that the motor ismicrostepped. Refer to Figure 30 for the resultingwaveform for the chopper drive microstepping.
DS00002326A-page 24 2017 Microchip Technology Inc.
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Motor Fault Detection FeatureIn order to avoid system failure or motor driverperformance degradation, appropriate early Faultdetection strategies are implemented in thisapplication.
Over-Current DetectionA good reason to run a stepper motor at a higher supplyvoltage is to push the maximum rated current throughthe motor windings. Running at a higher voltage leadsto a faster current rise time that leads to a high-torqueresponse at a higher speed when added with a chopperdrive. Although stepper motor can be driven at a highervoltage level, conditions such as winding isolationbreakdown and overheating can still be a risk whenvoltage and current goes too high. To avoid excessivewinding current and to limit the current through thewindings, over-current detection can be implemented.
To implement over-current detection, a RSHUNT isadded to the drive circuitry, giving a voltagecorresponding to the current flowing in the motorwinding. The voltage drop across this resistor varieslinearly with respect to the motor current. The voltageis fed to the inverting input of the Comparator andcompared with a certain reference voltage. Thisreference voltage is based on the product of RSHUNTresistance and the maximum allowable stall current ofthe motor. The reference voltage can be provided bythe FVR which can be narrowed down further by the
DAC. In this manner, very small reference voltage canbe used, allowing the RSHUNT resistance to be keptlow. Keeping the resistance low reduces the RSHUNTpower dissipation. If the RSHUNT voltage exceeds thereference, the comparator output will trigger the Autoshutdown feature of the COG.
Ambient Temperature DetectionAmbient Temperature can be detected using the deviceon-chip temperature indicator peripheral present on thePIC16F177X family. The indicator measures devicetemperature, corresponding to the temperature in itsenvironment with some delay. It allows the drivesystem to lower the current limit based on the ambienttemperature, letting the motor operate at a desirabletemperature.
The indicator is used to measure the devicetemperature between -40°C and +85°C. The internalcircuit of the temperature indicator produces a variablevoltage relative to temperature using internal transistorjunction threshold voltage. This voltage is converted todigital form by the Analog-to-Digital Converter (ADC).The ADC result will be used to determine the actualtemperature reading defined by Equation 10. For amore accurate temperature indicator reading, a single-point calibration is implemented. Refer to ApplicationNote AN1333, “Use and Calibration of the InternalTemperature Indicator” for more details regarding thecalibration process.
EQUATION 10: TEMPERATURE READING CALCULATION
The implementation of the overtemperature detectionuses the ADC internal channel input selection (CHS)bit. The temperature indicator module is used as thechannel input for the ADC. For every Timer interrupt,the completed ADC conversion result will be comparedwith the desired maximum temperature limit. When theADC result exceeds the maximum temperature limit,the output of the COG is disabled.
2017 Microchip Technology Inc. DS00002326A-page 25
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Motor Stall DetectionUnder normal conditions, when the motor is spinning, itgives periodic Back-EMF signals on both windings. Inthe case of a stalled motor, there is a little to no BEMFsignal produced. Hence, by monitoring when the motorstops producing these signals, the motor stall conditioncan also be detected. To implement motor stall detec-
tion, Level-Triggered Hardware Limit Timer (HLT)mode in Timer2/4/6 peripheral is used. For more detailsregarding the HLT, refer to TB3122, “Hardware LimitTimer on PIC® Microcontrollers”. Its main function is tomonitor any changes in the periodic Back EMF signal.Refer to Figure 31 for HLT implementation on motorcontrol design.
FIGURE 31: HLT STALL DETECTION
In this application, the outputs of Comparator 1 andComparator 2, whose inputs are connected to motorWinding A+ and Winding B+, respectively, are used asthe external signal source for the Timer2/4 HLT. Themotor produces Back EMF signals ranging from 50 kHz(20uS) to 400Hz (2.5mS) depending on the motorspeed. The period (PR) register of the Timer2/4 is thenset to a value that is sufficiently larger than theminimum input frequency (400Hz). By doing this, themotor stall condition can be detected at a much widerspeed range. Refer to Equation 11 for the PR valuecalculation.
EQUATION 11: PR2 CALCULATION
The reason for a larger PR value is for the input signalto occur first and reset the Timer2/4 count before thePR period match occurs. In the case of a rotating motor,
Back EMF pulses are always present to continuouslyreset the Timer2/4 count, preventing the period matchfrom occurring. Otherwise, in a case of stalled motor,Back EMF pulses are not present to reset the Timer2/4count, hence the timer continues to increment until theperiod match occurs. An interrupt event is triggeredevery time period match occurs. This can be used toshut down the COG output and indicate that the motoris not spinning or in a stall condition. Refer to Figure 32for the implementation of HLT mode as stall detection.
C1
H-BridgeDriver Stepper Motor
DAC
/8/4 Shutdown Signal
Winding A+ Back EMF Signal
C2
DAC
Timer2/4HLT Mode
COG 1/2
FVR
Winding B+ Back EMF Signal
PR TMR2 4 Clock Source Input Signal MIN Prescaler Postscaler-------------------------------------------------------------------------------------------------------------------
DS00002326A-page 26 2017 Microchip Technology Inc.
AN2326
FIGURE 32: HLT MODE IMPLEMENTATION
FIGURE 33: HLT STALL DETECTION
BEMF A/BC1/C2OUT
Motor Normal Running Condition
Motor Stall Condition
150PR Register Value
Timer Clock
Timer Count
Reset Signal
1 2 3 4 5 . . .
121
1 2 3 4 5 . . .
Timer2/4Interrupt
Motor stalled at this point
150
Timer Clock
Timer Count 1 2 3 4 5 . . .
121
TimerInterrupt
PR Value
150 PR and Timer Count Matched at this point
(PR Match)
BEMF A/BC1/C2OUT
Widning A
Winding B
HLTInterrupt Flag
Motor Normal Running Condition Motor Stall Condition
2017 Microchip Technology Inc. DS00002326A-page 27
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CONCLUSIONIn a stepper motor application where precisemeasurement, current control, fault detection and high-torque output is needed, an efficient and flexiblemicrocontroller that can accommodate all thesefeatures can provide an advantage and significantimpact. This application note describes how thePIC16F1776/9 microcontroller meets theserequirements.
The microcontroller is able to drive all the differenttypes of stepping motors. Full-step, wave, and half-stepdrive techniques are well within the capability of themicrocontroller. The step resolution, accuracy, andmotor resonance reduction can also be improvedthrough microstepping and current limiting techniques.The available Core Independent Peripherals such asCOG, 16-bit PWM, 10-bit DAC and high-speedcomparator allow for the implementation of moreadvanced stepper motor control techniques, such aschopper drive microstepping. For added applicationflexibility, an option for constant-torque or high-torquemicrostepping can also be implemented. Also, differentmotor fault detection methods can be employed toensure a safe and proper drive control. In addition, theuse of CIP’s to accomplish these features will give theuser a lot of spare capacity in the microcontroller toimplement any product-specific features.
DS00002326A-page 28 2017 Microchip Technology Inc.
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APP
END
IX A
:C
IRC
UIT
SC
HEM
ATI
C
FIG
UR
E A
-1:
HIG
H-T
OR
QU
E ST
EPPE
R M
OTO
R D
RIV
ER U
SIN
G P
IC16
F177
6/9
FDS
3992
FDS3
992
WIN
DIN
G B
’
33R
33R
10k
10k
FAN
7384
14 13 12 11 10 9 8
1 2 3 4 5 6 7
LIN
SD
HIN
VD
D
FO CS
C
VSS
VB
HO VS
NC
NC
LO VSL
3.3u
F/50
V+B
AT41
50R
15V
CO
G1B
CO
G1A
15V 0.
1uF
10k
10k
DC
+
FDS
3992
FDS
3992W
IND
ING
B
33R
33R
10k
10k
FAN
7384
14 13 12 11 10 9 8
1 2 3 4 5 6 7
LIN
SD
HIN
VDD
FO CS
C
VSS
VB
HO VS
NC
NC
LO VSL
3.3u
F/50
V+
BAT
4150
R
15V
CO
G1B
CO
G1A
15V
0.1u
F10
k
10k
DC
+
SHU
NT_
2
0.1R
/2W
SHU
NT_
2_G
ND
FDS
3992
FDS3
992
WIN
DIN
G A
’
33R
33R
10k
10k
FAN
7384
14 13 12 11 10 9 8
1 2 3 4 5 6 7
LIN
SD
HIN
VD
D
FO CS
C
VSS
VB
HO VS
NC
NC
LO VSL
3.3u
F/50
V+B
AT41
50R
15V
CO
G1B
CO
G1A
15V 0.
1uF
10k
10k
DC
+
FDS
3992
FDS
3992W
IND
ING
A
33R
33R
10k
10k
FAN
7384
14 13 12 11 10 9 8
1 2 3 4 5 6 7
LIN
SD
HIN
VDD
FO CS
C
VSS
VB
HO VS
NC
NC
LO VSL
3.3u
F/50
V+
BAT
4150
R
15V
CO
G1B
CO
G1A
15V
0.1u
F10
k
10k
DC
+
SHU
NT_
1
0.1R
/2W
SHU
NT_
1_G
ND
Step
per
Mot
or
Winding A
Win
ding
B
B+B
-
WIN
IDN
G A
WIN
DIN
G A
’
WIN
IDN
G B
WIN
IDN
G B
’
PIC
16F1
776/
9
10
CO
G2C
CO
G2B
CO
G2A
CO
G1D
CO
G1C
CO
G1B
CO
G1A
MC
LR
U1
11 12 13 14
19 18 17 16 1524 23 22 21 2028 27 26 25
5 6 7 8 91 2 3 4
VSS
C1I
N-/S
HU
NT_
1
C2I
N-/S
HU
NT_
2
CO
G2D
VDD
VSS
MC
7815
CD
2T/R
4
CC
0.1u
FC
47uF
VIN
VO
UT
GND 1
23
100u
F
++
+
1 3 2
+15 V
DC
+
+15V
SU
PPLY
KLD
X-02
02-A
GN
D (-
)
VIN
(+)
BP1
BP2
+C 470u
FC
0.1u
F
DC
+M
CP
1703
T-33
02E/
MB
CC
220u
FC
1.0u
F
VIN
VOU
T
GND 1
23
220u
F
++
+VDD
+5V
2017 Microchip Technology Inc. DS00002326A-page 29
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APPENDIX B: CIP PERFORMANCE EVALUATION
TABLE B-1: COG IN DRIVING H-BRIDGE CIRCUIT
TABLE B-2: RESOURCE COMPARISON
OperationH-Bridge Drive Using COG H-Bridge Drive Using Conventional Method
Availability Execution Time Advantage/Limitation Availability Execution
Time Advantage/Limitation
Shoot-Through Current Protection
Yes
1 instruction
cycle or FOSC/4
5-bit Resolution available on all COG
mode provide selection of Synchronous and Asynchronous Delay
DS00002326A-page 30 2017 Microchip Technology Inc.
Note the following details of the code protection feature on Microchip devices:• Microchip products meet the specification contained in their particular Microchip Data Sheet.
• Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions.
• There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
• Microchip is willing to work with the customer who is concerned about the integrity of their code.
• Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of ourproducts. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such actsallow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Information contained in this publication regarding deviceapplications and the like is provided only for your convenienceand may be superseded by updates. It is your responsibility toensure that your application meets with your specifications.MICROCHIP MAKES NO REPRESENTATIONS ORWARRANTIES OF ANY KIND WHETHER EXPRESS ORIMPLIED, WRITTEN OR ORAL, STATUTORY OROTHERWISE, RELATED TO THE INFORMATION,INCLUDING BUT NOT LIMITED TO ITS CONDITION,QUALITY, PERFORMANCE, MERCHANTABILITY ORFITNESS FOR PURPOSE. Microchip disclaims all liabilityarising from this information and its use. Use of Microchipdevices in life support and/or safety applications is entirely atthe buyer’s risk, and the buyer agrees to defend, indemnify andhold harmless Microchip from any and all damages, claims,suits, or expenses resulting from such use. No licenses areconveyed, implicitly or otherwise, under any Microchipintellectual property rights unless otherwise stated.
2017 Microchip Technology Inc.
Microchip received ISO/TS-16949:2009 certification for its worldwide headquarters, design and wafer fabrication facilities in Chandler and Tempe, Arizona; Gresham, Oregon and design centers in California and India. The Company’s quality system processes and procedures are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping devices, Serial EEPROMs, microperipherals, nonvolatile memory and analog products. In addition, Microchip’s quality system for the design and manufacture of development systems is ISO 9001:2000 certified.
QUALITY MANAGEMENT SYSTEM CERTIFIED BY DNV
== ISO/TS 16949 ==
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ClockWorks, The Embedded Control Solutions Company, EtherSynch, Hyper Speed Control, HyperLight Load, IntelliMOS, mTouch, Precision Edge, and Quiet-Wire are registered trademarks of Microchip Technology Incorporated in the U.S.A.
Adjacent Key Suppression, AKS, Analog-for-the-Digital Age, Any Capacitor, AnyIn, AnyOut, BodyCom, chipKIT, chipKIT logo, CodeGuard, CryptoAuthentication, CryptoCompanion, CryptoController, dsPICDEM, dsPICDEM.net, Dynamic Average Matching, DAM, ECAN, EtherGREEN, In-Circuit Serial Programming, ICSP, Inter-Chip Connectivity, JitterBlocker, KleerNet, KleerNet logo, Mindi, MiWi, motorBench, MPASM, MPF, MPLAB Certified logo, MPLIB, MPLINK, MultiTRAK, NetDetach, Omniscient Code Generation, PICDEM, PICDEM.net, PICkit, PICtail, PureSilicon, QMatrix, RightTouch logo, REAL ICE, Ripple Blocker, SAM-ICE, Serial Quad I/O, SMART-I.S., SQI, SuperSwitcher, SuperSwitcher II, Total Endurance, TSHARC, USBCheck, VariSense, ViewSpan, WiperLock, Wireless DNA, and ZENA are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries.
SQTP is a service mark of Microchip Technology Incorporated in the U.S.A.
Silicon Storage Technology is a registered trademark of Microchip Technology Inc. in other countries.
GestIC is a registered trademark of Microchip Technology Germany II GmbH & Co. KG, a subsidiary of Microchip Technology Inc., in other countries.
All other trademarks mentioned herein are property of their respective companies.
