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Charge pump design for high-voltage biasing applications in piezoelectric-based miniaturized robots A. Saiz-Vela Æ P. Miribel-Catala Æ J. Colomer Æ M. Puig-Vidal Æ J. Samitier Recei ved: 30 Novembe r 2007 / Revis ed: 30 Novembe r 2007 / Acce pted: 14 Novemb er 2008 / Publis hed online: 9 Decemb er 2008 Ó Springer Science+Business Media, LLC 2008 Abstract Fully autonomous piezoe lectric -base d minia - turized robots usually have a high-voltage biasing system that provides the required voltage levels to drive properly their piezoelectric actuators. In this paper a novel on-board biasing system based on the cascade connection of three full-custom charge pump ICs is presented. Simulated and experimental results show that the proposed biasing system is capable to obtain a regulated output voltage up to 20 V fr om a 3. 3 V ba tt ery and de li ve r successf ul ly up to 120 mW of powe r. Moreover, a novel appr oach in the ste ady -state ana lys is of the two -phase vol tage dou ble r (which is the core of the designed charge pump IC) has been developed in order to have a tool capable to provide a ful l und ers tanding of the ste ady-sta te vol tage dou ble r’s behavior while at the same time accelerate and simplify the design process of such circuit. Simulated results show that the propos ed mat hema tica l mod el is more acc urat e tha n already developed models. The design of the charge pump IC ha s been impl emented using a commer ci al 0. 7 lm Bipolar-CMOS-DMOS (BCD) technology. Keywords Charg e pumps Á Switched-capacitor DC–DC converters Á Pulse skippi ng regula tion Á Efficiency improvement 1 Intro ductio n The use of miniaturized robots in applications where high pre cis ion is requir ed like cel l man ipulati on [ 1] or AFM surface scanning [2] is a very active research field. Nano- walker [3], MINIMAN [4] and MiCRoN [5] are successful examples of miniaturized robots that have been developed to do such precise tasks. All of these robots have in com- mon the use of piezoelectric (PZT) actuators and, some of them, can also be autonomous due to the use of on-board bat ter ies [3, 5]. Howe ver, PZT actuat or s need hi gher voltage values than the one provided by the battery to be fully functional (up to 50 V for MINIMAN robots, up to 20 V for MiCRoN robots). Hence, the generation of such high voltage values and efficient power saving strategies ar e key points that must be taken into account when the on- boa rd bia sing sys tem of a miniat uriz ed robot is designed. The presented work has been done in the framework of the Eur ope an res ear ch pro jec t MiCRoN whi ch has bee n focused in the deve lop me nt of 1 cm 3 battery-powered autonomous robots capable to execute handling or manip- ulatio n tasks in biolog ical experiments where accur acies within the micro and nano range are required. Although the main circuitry in such devices is biased by a 3.3 V battery, some PZT actuators mounted on them need signals up to 20 V to be driven [6]. Two different circuits can be used to obtain such high-v oltage value: induct or-bas ed DC–DC convert er s or switc hed-c apacito r DC–DC conver ters (commonly kno wn as cha rge pumps) [7]. The induct or- based approach offers good efficiency results for a wide range of loads but the use of external inductors generates electromagnetic interferences (EMI) that may disturb the cor rec t functional ity of other har dwa re dev ice s in the str uct ure of the robots like the wir ele ss communica tion A. Saiz-Vela (&) Á P. Miribel-Catala Á J. Colomer Á M. Puig-Vidal Á J. Samitier Systems for Instrumentation and Communications (SIC) Lab., Dept. Electro ` nica, Universitat de Barcelona, Martı ´ i Franque ` s 1, 08028 Barcelona, Spain e-mail: [email protected] 123 Analo g Integ r Circ Sig Proce ss (2009) 59:169–1 84 DOI 10.1007/s10470-008-9255-9
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