Ads 1232

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1/37

1

F E A T U R E S D E S C R I P T I O N

A P P L I C A T I O N S

Input

MuxDS ADC

REFP REFN

PGA

Gain=

1,2,64,or128

CAP DVDD

DGNDAGNDA1/TEMP(1)

A0

NOTE:(1)A1forADS1234,TEMPforADS1232.

AINP1

AINN1

AINP2

AINN2

AINP3

AINN3

AINP4

AINN4

ADS1234

Only

SCLK

SPEED

DRDY/DOUT

PDWN

GAIN[1:0]

AVDD

CAP

ExternalOscillator

InternalOscillator

CLKIN/XTAL1 XTAL2

A D S 1 2 3 2

A D S 1 2 3 4

S B A S 3 5 0 F J U N E 2 0 0 5 R E V I S E D F E B R U A R Y 2 0 0 8 w w w . t i . c o m

2 4 - B i t A n a l o g - t o - D i g i t a l C o n v e r t e r F o r B r i d g e S e n s o r s

2 C o m p l e t e F r o n t - E n d f o r B r i d g e S e n s o r s T h e A D S 1 2 3 2 a n d A D S 1 2 3 4 a r e p r e c i s i o n 2 4 - b i t a n a l o g - t o - d i g i t a l c o n v e r t e r s ( A D C s ) . W i t h a n o n b o a r d , U p t o 2 3 . 5 E f f e c t i v e B i t s l o w - n o i s e p r o g r a m m a b l e g a i n a m p l i f i e r ( P G A ) , O n b o a r d , L o w - N o i s e P G A p r e c i s i o n d e l t a - s i g m a A D C a n d i n t e r n a l o s c i l l a t o r , t h e

R M S N o i s e : A D S 1 2 3 2 / 4 p r o v i d e a c o m p l e t e f r o n t - e n d s o l u t i o n f o r 1 7 n V a t 1 0 S P S ( P G A = 1 2 8 ) b r i d g e s e n s o r a p p l i c a t i o n s i n c l u d i n g w e i g h s c a l e s , 4 4 n V a t 8 0 S P S ( P G A = 1 2 8 ) s t r a i n g a u g e s a n d p r e s s u r e s e n s o r s .

1 9 . 2 - B i t N o i s e - F r e e R e s o l u t i o n a t G a i n = 6 4 T h e i n p u t m u l t i p l e x e r a c c e p t s e i t h e r t w o ( A D S 1 2 3 2 ) O v e r 1 0 0 d B S i m u l t a n e o u s 5 0 H z a n d 6 0 H z o r f o u r ( A D S 1 2 3 4 ) d i f f e r e n t i a l i n p u t s . T h e A D S 1 2 3 2

a l s o i n c l u d e s a n o n b o a r d t e m p e r a t u r e s e n s o r t o R e j e c t i o n m o n i t o r a m b i e n t t e m p e r a t u r e . T h e o n b o a r d , l o w - n o i s e F l e x i b l e C l o c k i n g : P G A h a s a s e l e c t a b l e g a i n o f 1 , 2 , 6 4 , o r 1 2 8 L o w - D r i f t O n b o a r d O s c i l l a t o r ( 3 % )

s u p p o r t i n g a f u l l - s c a l e d i f f e r e n t i a l i n p u t o f 2 . 5 V , O p t i o n a l E x t e r n a l C r y s t a l 1 . 2 5 V , 3 9 m V , o r 1 9 . 5 m V . T h e d e l t a - s i g m a A D C S e l e c t a b l e G a i n s o f 1 , 2 , 6 4 , a n d 1 2 8 h a s 2 3 . 5 - b i t e f f e c t i v e r e s o l u t i o n a n d i s c o m p r i s e d o f a

3 r d - o r d e r m o d u l a t o r a n d 4 t h - o r d e r d i g i t a l f i l t e r . T w o E a s y R a t i o m e t r i c M e a s u r e m e n t s d a t a r a t e s a r e s u p p o r t e d : 1 0 S P S ( w i t h b o t h 5 0 H z a n d E x t e r n a l V o l t a g e R e f e r e n c e u p t o 5 V 6 0 H z r e j e c t i o n ) a n d 8 0 S P S . T h e A D S 1 2 3 2 / 4 c a n b e

S e l e c t a b l e 1 0 S P S o r 8 0 S P S D a t a R a t e s c l o c k e d e x t e r n a l l y u s i n g a n o s c i l l a t o r o r a c r y s t a l .

T w o - C h a n n e l D i f f e r e n t i a l I n p u t w i t h B u i l t - I n T h e r e i s a l s o a n i n t e r n a l o s c i l l a t o r a v a i l a b l e t h a t T e m p e r a t u r e S e n s o r ( A D S 1 2 3 2 ) r e q u i r e s n o e x t e r n a l c o m p o n e n t s . O f f s e t c a l i b r a t i o n i s

p e r f o r m e d o n - d e m a n d a n d t h e A D S 1 2 3 2 / 4 c a n b e F o u r - C h a n n e l D i f f e r e n t i a l I n p u t ( A D S 1 2 3 4 ) p u t i n a l o w - p o w e r s t a n d b y m o d e o r s h u t o f f

S i m p l e S e r i a l D i g i t a l I n t e r f a c e c o m p l e t e l y i n p o w e r - d o w n m o d e . A l l o f t h e f e a t u r e s o f S u p p l y R a n g e : 2 . 7 V t o 5 . 3 V t h e A D S 1 2 3 2 / 4 a r e o p e r a t e d t h r o u g h s i m p l e

p i n - d r i v e n c o n t r o l . T h e r e a r e n o d i g i t a l r e g i s t e r s t o 4 0 C t o + 1 0 5 C T e m p e r a t u r e R a n g e

p r o g r a m i n o r d e r t o s i m p l i f y s o f t w a r e d e v e l o p m e n t . D a t a a r e o u t p u t o v e r a n e a s i l y - i s o l a t e d s e r i a l i n t e r f a c e t h a t c o n n e c t s d i r e c t l y t o t h e M S P 4 3 0 a n d

W e i g h S c a l e s o t h e r m i c r o c o n t r o l l e r s . S t r a i n G a u g e s

T h e A D S 1 2 3 2 i s a v a i l a b l e i n a T S S O P - 2 4 p a c k a g e P r e s s u r e S e n s o r s

a n d t h e A D S 1 2 3 4 i s i n a T S S O P - 2 8 . B o t h a r e f u l l y I n d u s t r i a l P r o c e s s C o n t r o l s p e c i f i e d f r o m - 4 0 C t o + 1 0 5 C .

1

P l e a s e b e a w a r e t h a t a n i m p o r t a n t n o t i c e c o n c e r n i n g a v a i l a b i l i t y , s t a n d a r d w a r r a n t y , a n d u s e i n c r i t i c a l a p p l i c a t i o n s o f T e x a s I n s t r u m e n t s s e m i c o n d u c t o r p r o d u c t s a n d d i s c l a i m e r s t h e r e t o a p p e a r s a t t h e e n d o f t h i s d a t a s h e e t .

2 A l l t r a d e m a r k s a r e t h e p r o p e r t y o f t h e i r r e s p e c t i v e o w n e r s .

P R O D U C T I O N D A T A i n f o r m a t i o n i s c u r r e n t a s o f p u b l i c a t i o n d a t e . C o p y r i g h t 2 0 0 5 2 0 0 8 , T e x a s I n s t r u m e n t s I n c o r p o r a t e d P r o d u c t s c o n f o r m t o s p e c i f i c a t i o n s p e r t h e t e r m s o f t h e T e x a s I n s t r u m e n t s s t a n d a r d w a r r a n t y . P r o d u c t i o n p r o c e s s i n g d o e s n o t

n e c e s s a r i ly i n c l u d e t e s t i n g o f a l l p a r a m e t e r s .
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O R D E R I N G I N F O R M A T I O N

A B S O L U T E M A X I M U M R A T I N G S

A D S 1 2 3 2

A D S 1 2 3 4

S B A S 3 5 0 F J U N E 2 0 0 5 R E V I S E D F E B R U A R Y 2 0 0 8

T h i s i n t e g r a t e d c i r c u i t c a n b e d a m a g e d b y E S D . T e x a s I n s t r u m e n t s r e c o m m e n d s t h a t a l l i n t e g r a t e d c i r c u i t s b e h a n d l e d w i t h a p p r o p r i a t e p r e c a u t i o n s . F a i l u r e t o o b s e r v e p r o p e r h a n d l i n g a n d i n s t a l l a t i o n p r o c e d u r e s c a n c a u s e d a m a g e .

E S D d a m a g e c a n r a n g e f r o m s u b t l e p e r f o r m a n c e d e g r a d a t i o n t o c o m p l e t e d e v i c e f a i l u r e . P r e c i s i o n i n t e g r a t e d c i r c u i t s m a y b e m o r e s u s c e p t i b l e t o d a m a g e b e c a u s e v e r y s m a l l p a r a m e t r i c c h a n g e s c o u l d c a u s e t h e d e v i c e n o t t o m e e t i t s p u b l i s h e d s p e c i f i c a t i o n s .

F o r t h e m o s t c u r r e n t p a c k a g e a n d o r d e r i n g i n f o r m a t i o n , s e e t h e P a c k a g e O p t i o n A d d e n d u m a t t h e e n d o f t h i s d a t a s h e e t , o r s e e t h e T I w e b s i t e a t w w w . t i . c o m .

o v e r o p e r a t i n g f r e e - a i r t e m p e r a t u r e r a n g e ( u n l e s s o t h e r w i s e n o t e d ) ( 1 )

A D S 1 2 3 2 , A D S 1 2 3 4 U N I T

A V D D t o A G N D 0 . 3 t o + 6 V

D V D D t o D G N D 0 . 3 t o + 6 V

A G N D t o D G N D 0 . 3 t o + 0 . 3 V

I n p u t C u r r e n t 1 0 0 , M o m e n t a r y m A

I n p u t C u r r e n t 1 0 , C o n t i n u o u s m A

A n a l o g I n p u t V o l t a g e t o A G N D 0 . 3 t o A V D D + 0 . 3 V

D i g i t a l I n p u t V o l t a g e t o D G N D 0 . 3 t o D V D D + 0 . 3 V

M a x i m u m J u n c t i o n T e m p e r a t u r e + 1 5 0 C

O p e r a t i n g T e m p e r a t u r e R a n g e 4 0 t o + 1 0 5 C

S t o r a g e T e m p e r a t u r e R a n g e 6 0 t o + 1 5 0 C

( 1 ) S t r e s s e s b e y o n d t h o s e l i s t e d u n d e r A b s o l u t e M a x i m u m R a t i n g s m a y c a u s e p e r m a n e n t d a m a g e t o t h e d e v i c e . T h e s e a r e s t r e s s r a t i n g s o n l y , a n d f u n c t i o n a l o p e r a t i o n o f t h e d e v i c e a t t h e s e o r a n y o t h e r c o n d i t i o n s b e y o n d t h o s e i n d i c a t e d u n d e r R e c o m m e n d e d O p e r a t i n gC o n d i t i o n s i s n o t i m p l i e d . E x p o s u r e t o a b s o l u t e - m a x i m u m - r a t e d c o n d i t i o n s f o r e x t e n d e d p e r i o d s m a y a f f e c t d e v i c e r e l i a b i l i t y .

2 C o p y r i g h t 2 0 0 5 2 0 0 8 , T e x a s I n s t r u m e n t s I n c o r p o r a t e d

P r o d u c t F o l d e r L i n k ( s ) : A D S 1 2 3 2 A D S 1 2 3 4
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E L E C T R I C A L C H A R A C T E R I S T I C S

A D S 1 2 3 2

A D S 1 2 3 4


A l l s p e c i f i c a t i o n s a t T A = 4 0 C t o + 1 0 5 C , A V D D = D V D D = V R E F P = + 5 V , a n d V R E F N = A G N D , u n l e s s o t h e r w i s e n o t e d .

A D S 1 2 3 2 , A D S 1 2 3 4

P A R A M E T E R C O N D I T I O N S M I N T Y P M A X U N I T

A n a l o g I n p u t s

F u l l - S c a l e I n p u t V o l t a g e

0 . 5 V R E F/ G a i n V ( A I N P A I N N )

A I N x P o r A I N x N w i t h r e s p e c t t o G N D , A G N D 0 . 1 A V D D + 0 . 1 V

G a i n = 1 , 2 C o m m o n - M o d e I n p u t R a n g e

G a i n = 6 4 , 1 2 8 A G N D + 1 . 5 V A V D D 1 . 5 V V

G a i n = 1 3 n A

D i f f e r e n t i a l I n p u t C u r r e n t G a i n = 2 6 n A

G a i n = 6 4 , 1 2 8 3 . 5 n A

S y s t e m P e r f o r m a n c e

R e s o l u t i o n N o M i s s i n g C o d e s 2 4 B i t s

I n t e r n a l O s c i l l a t o r , S P E E D = H i g h 7 8 8 0 8 2 . 4 S P S

I n t e r n a l O s c i l l a t o r , S P E E D = L o w 9 . 7 5 1 0 1 0 . 3 S P S D a t a R a t e

E x t e r n a l O s c i l l a t o r , S P E E D = H i g h f C L K/ 6 1 , 4 4 0 S P S

E x t e r n a l O s c i l l a t o r , S P E E D = L o w f C L K/ 4 9 1 , 5 2 0 S P S

D i g i t a l F i l t e r S e t t l i n g T i m e F u l l S e t t l i n g 4 C o n v e r s i o n s

D i f f e r e n t i a l I n p u t , E n d - P o i n t F i t 0 . 0 0 0 2 0 . 0 0 1 % o f F S R ( 1 )

G a i n = 1 , 2 I n t e g r a l N o n l i n e a r i t y ( I N L )

D i f f e r e n t i a l I n p u t , E n d - P o i n t F i t 0 . 0 0 0 4 % o f F S R

G a i n = 6 4 , 1 2 8

G a i n = 1 0 . 2 5 p p m o f F S I n p u t O f f s e t E r r o r ( 2 )

G a i n = 1 2 8 0 . 0 2 1 p p m o f F S

G a i n = 1 0 . 3 V / CI n p u t O f f s e t D r i f t

G a i n = 1 2 8 1 0 n V / C

G a i n = 1 0 . 0 0 1 0 . 0 2 % G a i n E r r o r ( 3 )

G a i n = 1 2 8 0 . 0 1 0 . 1 %

G a i n = 1 0 . 2 p p m / CG a i n D r i f t

G a i n = 1 2 8 2 . 5 p p m / C

I n t e r n a l O s c i l l a t o r , f D A T A = 1 0 S P S 1 0 0 1 1 0 d B fI N = 5 0 H z o r 6 0 H z , 1 H z

N o r m a l - M o d e R e j e c t i o n ( 4 )

E x t e r n a l O s c i l l a t o r , f D A T A = 1 0 S P S 1 2 0 1 3 0 d B fI N = 5 0 H z o r 6 0 H z , 1 H z

a t D C , G a i n = 1 , V = 1 V 9 5 1 1 0 d B C o m m o n - M o d e R e j e c t i o n

a t D C , G a i n = 1 2 8 , V = 0 . 1 V 9 5 1 1 0 d B

I n p u t - R e f e r r e d N o i s e S e e N o i s e P e r f o r m a n c e T a b l e s

a t D C , G a i n = 1 , V = 1 V 1 0 0 1 2 0 d B P o w e r - S u p p l y R e j e c t i o n

a t D C , G a i n = 1 2 8 , V = 0 . 1 V 1 0 0 1 2 0 d B

V o l t a g e R e f e r e n c e I n p u t

V o l t a g e R e f e r e n c e I n p u t ( V R E F) VR E F = V R E F P V R E F N 1 . 5 A V D D A V D D + 0 . 1 V V

N e g a t i v e R e f e r e n c e I n p u t ( V R E F N ) A G N D 0 . 1 V R E F P 1 . 5 V

P o s i t i v e R e f e r e n c e I n p u t ( V R E F P ) V R E F N + 1 . 5 A V D D + 0 . 1 V

V o l t a g e R e f e r e n c e 1 0 n A I n p u t C u r r e n t

( 1 ) F S R = f u l l - s c a l e r a n g e = V R E F/ G a i n . ( 2 ) O f f s e t c a l i b r a t i o n c a n m i n i m i z e t h e s e e r r o r s t o t h e l e v e l o f n o i s e a t a n y t e m p e r a t u r e . ( 3 ) G a i n e r r o r s a r e c a l i b r a t e d a t t h e f a c t o r y ( A V D D = + 5 V , a l l g a i n s , T A = + 2 5 C ) .( 4 ) S p e c i f i c a t i o n i s a s s u r e d b y t h e c o m b i n a t i o n o f d e s i g n a n d f i n a l p r o d u c t i o n t e s t .

C o p y r i g h t 2 0 0 5 2 0 0 8 , T e x a s I n s t r u m e n t s I n c o r p o r a t e d 3

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A D S 1 2 3 2

A D S 1 2 3 4


E L E C T R I C A L C H A R A C T E R I S T I C S ( c o n t i n u e d ) A l l s p e c i f i c a t i o n s a t T A = 4 0 C t o + 1 0 5 C , A V D D = D V D D = V R E F P = + 5 V , a n d V R E F N = A G N D , u n l e s s o t h e r w i s e n o t e d .

A D S 1 2 3 2 , A D S 1 2 3 4

P A R A M E T E R C O N D I T I O N S M I N T Y P M A X U N I T

D i g i t a l

L o g i c L e v e l s

VI H 0 . 7 D V D D D V D D + 0 . 1 V

VI L D G N D 0 . 2 D V D D V

VO H IO H = 1 m A D V D D 0 . 4 V

VO L IO L = 1 m A 0 . 2 D V D D V

I n p u t L e a k a g e 0 < V I N < D V D D 1 0 A

E x t e r n a l C l o c k I n p u t F r e q u e n c y 0 . 2 4 . 9 1 5 2 8 M H z

( fC L K I N )

S e r i a l C l o c k I n p u t F r e q u e n c y ( f S C L K ) 5 M H z

P o w e r S u p p l y

P o w e r - S u p p l y V o l t a g e 2 . 7 5 . 3 V

( A V D D , D V D D )

N o r m a l M o d e , A V D D = 3 V , 6 0 0 1 3 0 0 A

G a i n = 1 , 2

N o r m a l M o d e , A V D D = 3 V , 1 3 5 0 2 5 0 0 AG a i n = 6 4 , 1 2 8

N o r m a l M o d e , A V D D = 5 V , 6 5 0 1 3 0 0 AA n a l o g S u p p l y C u r r e n t G a i n = 1 , 2

N o r m a l M o d e , A V D D = 5 V , 1 3 5 0 2 5 0 0 A

G a i n = 6 4 , 1 2 8

S t a n d b y M o d e 0 . 1 1 A

P o w e r - D o w n 0 . 1 1 A

N o r m a l M o d e , D V D D = 3 V , 6 0 9 5 A

G a i n = 1 , 2

N o r m a l M o d e , D V D D = 3 V , 7 5 1 2 0 A

G a i n = 6 4 , 1 2 8

N o r m a l M o d e , D V D D = 5 V , 9 5 1 3 0 A

G a i n = 1 , 2 D i g i t a l S u p p l y C u r r e n t

N o r m a l m o d e , D V D D = 5 V , 7 5 1 2 0 A

G a i n = 6 4 , 1 2 8 S t a n d b y M o d e , S C L K = H i g h , D V D D = 3 V 4 5 8 0 A

S t a n d b y M o d e , S C L K = H i g h , D V D D = 5 V 6 5 8 0 A

P o w e r - D o w n 0 . 2 1 . 3 A

N o r m a l M o d e , A V D D = D V D D = 3 V , 2 4 . 2 m W

G a i n = 1 , 2

N o r m a l M o d e , A V D D = D V D D = 5 V , 3 . 7 7 . 2 m W

G a i n = 1 , 2

P o w e r D i s s i p a t i o n , T o t a l N o r m a l M o d e , A V D D = D V D D = 3 V , 4 . 3 7 . 9 m W

G a i n = 6 4 , 1 2 8

N o r m a l M o d e , A V D D = D V D D = 5 V , 7 . 1 1 3 . 1 m W

G a i n = 6 4 , 1 2 8

S t a n d b y M o d e , A V D D = D V D D = 5 V 0 . 3 0 . 4 m W



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N O I S E P E R F O R M A N C E

A D S 1 2 3 2

A D S 1 2 3 4


T h e A D S 1 2 3 2 / 4 o f f e r o u t s t a n d i n g n o i s e p e r f o r m a n c e t h a t c a n b e o p t i m i z e d f o r a g i v e n f u l l - s c a l e r a n g e u s i n g t h e o n - c h i p p r o g r a m m a b l e g a i n a m p l i f i e r . T a b l e 1 t h r o u g h T a b l e 4 s u m m a r i z e t h e t y p i c a l n o i s e p e r f o r m a n c e w i t h i n p u t s s h o r t e d e x t e r n a l l y f o r d i f f e r e n t g a i n s , d a t a r a t e s , a n d v o l t a g e r e f e r e n c e v a l u e s .

T h e R M S a n d P e a k - t o - P e a k n o i s e a r e r e f e r r e d t o t h e i n p u t . T h e E f f e c t i v e N u m b e r o f B i t s ( E N O B ) i s d e f i n e d a s :

E N O B = l n ( F S R / R M S n o i s e ) / l n ( 2 )

T h e N o i s e - F r e e B i t s a r e d e f i n e d a s :

N o i s e - F r e e B i t s = l n ( F S R / P e a k - t o - P e a k N o i s e ) / l n ( 2 )

W h e r e F S R ( F u l l - S c a l e R a n g e ) = V R E F/ G a i n

T a b l e 1 . A V D D = 5 V , V R E F = 5 V , D a t a R a t e = 1 0 S P S

G A I N R M S N O I S E P E A K - T O - P E A K N O I S E ( 1 ) E N O B ( R M S ) N O I S E - F R E E B I T S

1 4 2 0 n V 1 . 7 9 V 2 3 . 5 2 1 . 4

2 2 7 0 n V 9 0 0 n V 2 3 . 1 2 1 . 4

6 4 1 9 n V 1 2 5 n V 2 2 . 0 1 9 . 2

1 2 8 1 7 n V 1 1 0 n V 2 1 . 1 1 8 . 4

( 1 ) P e a k - t o - p e a k n o i s e d a t a a r e b a s e d o n d i r e c t m e a s u r e m e n t .



1 1 . 3 6 V 8 . 3 V 2 1 . 8 1 9 . 2

2 8 5 0 n V 5 . 5 V 2 1 . 5 1 8 . 8

6 4 4 8 n V 3 0 7 n V 2 0 . 6 1 8

1 2 8 4 4 n V 2 4 7 n V 1 9 . 7 1 7 . 2



G A I N R M S N O I S E P E A K - T O - P E A K N O I S E ( 1 )

E N O B ( R M S ) N O I S E - F R E E B I T S 1 4 5 0 n V 2 . 8 V 2 2 . 6 2 0

2 3 2 5 n V 1 . 8 V 2 2 . 1 1 9 . 7

6 4 2 0 n V 1 3 0 n V 2 1 . 2 1 8 . 5

1 2 8 1 8 n V 1 1 5 n V 2 0 . 3 1 7 . 6




1 2 . 2 V 1 2 V 2 0 . 4 1 7 . 9

2 1 . 2 V 6 . 8 V 2 0 . 2 1 7 . 8

6 4 5 4 n V 3 4 0 n V 1 9 . 7 1 7 . 1

1 2 8 4 8 n V 2 5 4 n V 1 8 . 9 1 6 . 5

( 1 ) P e a k - t o - p e a k n o i s e d a t a a r e b a s e d o n d i r e c t m e a s u r e m e n t o f 1 0 2 4 s a m p l e s .



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P I N C O N F I G U R A T I O N

DVDD

DGND

CLKIN/XTAL1

XTAL2

DGND

DGND

A1

A0

CAP

CAP

AINP1

AINN1

AINP3

AINN3

DRDY/DOUT

SCLK

PDWN

SPEED

GAIN1

GAIN0

AVDD

AGND

REFP

REFN

AINP2

AINN2

AINP4

AINN4

1

2

3

4

5

6

7

8

9

10

11

12

13

14

28

27

26

25

24

23

22

21

20

19

18

17

16

15

ADS1234

DVDD

DGND

CLKIN/XTAL1

XTAL2

DGND

DGND

TEMP

A0

CAP

CAP

AINP1

AINN1

DRDY/DOUT

SCLK

PDWN

SPEED

GAIN1

GAIN0

AVDD

AGND

REFP

REFN

AINP2

AINN2

1

2

3

4

5

6

7

8

9

10

11

12

24

23

22

21

20

19

18

17

16

15

14

13

ADS1232

A D S 1 2 3 2

A D S 1 2 3 4



http://focus.ti.com/docs/prod/folders/print/ads1232.htmlhttp://focus.ti.com/docs/prod/folders/print/ads1234.htmlhttp://focus.ti.com/docs/prod/folders/print/ads1232.htmlhttp://focus.ti.com/docs/prod/folders/print/ads1234.htmlhttp://focus.ti.com/docs/prod/folders/print/ads1232.html

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A D S 1 2 3 2

A D S 1 2 3 4


P I N D E S C R I P T I O N S

T E R M I N A L A N A L O G / D I G I T A L

N A M E A D S 1 2 3 2 A D S 1 2 3 4 I N P U T / O U T P U T D E S C R I P T I O N

D V D D 1 1 D i g i t a l D i g i t a l P o w e r S u p p l y : 2 . 7 V t o 5 . 3 V

D G N D 2 2 D i g i t a l D i g i t a l G r o u n d

C L K I N / E x t e r n a l C l o c k I n p u t : t y p i c a l l y 4 . 9 1 5 2 M H z . T i e l o w t o a c t i v a t e i n t e r n a l o s c i l l a t o r . C a n a l s o u s e 3 3 D i g i t a l / D i g i t a l I n p u t

X T A L 1 e x t e r n a l c r y s t a l a c r o s s C L K I N / X T A L 1 a n d X T A L 2 p i n s . S e e t e x t f o r m o r e d e t a i l s .

X T A L 2 4 4 D i g i t a l E x t e r n a l c r y s t a l c o n n e c t i o n



T E M P 7 D i g i t a l I n p u t O n b o a r d T e m p e r a t u r e D i o d e E n a b l e

I n p u t M u x S e l e c t I n p u t p i n ( M S B )

I n p u t M u x S e l e c t I n p u t p i n ( L S B ) :

A 1 A 0 C h a n n e l A 1 7

D i g i t a l I n p u t 0 0 A I N 1 A 0 8 8

0 1 A I N 2

1 0 A I N 3

1 1 A I N 4

C A P 9 9 A n a l o g G a i n A m p B y p a s s C a p a c i t o r C o n n e c t i o n

C A P 1 0 1 0 A n a l o g G a i n A m p B y p a s s C a p a c i t o r C o n n e c t i o n

A I N P 1 1 1 1 1 A n a l o g I n p u t P o s i t i v e A n a l o g I n p u t C h a n n e l 1

A I N N 1 1 2 1 2 A n a l o g I n p u t N e g a t i v e A n a l o g I n p u t C h a n n e l 1

A I N P 3 1 3 A n a l o g I n p u t P o s i t i v e A n a l o g I n p u t C h a n n e l 3

A I N N 3 1 4 A n a l o g I n p u t N e g a t i v e A n a l o g I n p u t C h a n n e l 3

A I N N 4 1 5 A n a l o g I n p u t N e g a t i v e A n a l o g I n p u t C h a n n e l 4

A I N P 4 1 6 A n a l o g I n p u t P o s i t i v e A n a l o g I n p u t C h a n n e l 4

A I N N 2 1 3 1 7 A n a l o g I n p u t N e g a t i v e A n a l o g I n p u t C h a n n e l 2

A I N P 2 1 4 1 8 A n a l o g I n p u t P o s i t i v e A n a l o g I n p u t C h a n n e l 2

R E F N 1 5 1 9 A n a l o g I n p u t N e g a t i v e R e f e r e n c e I n p u t

R E F P 1 6 2 0 A n a l o g I n p u t P o s i t i v e R e f e r e n c e I n p u t

A G N D 1 7 2 1 A n a l o g A n a l o g G r o u n d

A V D D 1 8 2 2 A n a l o g A n a l o g P o w e r S u p p l y , 2 . 7 V t o 5 . 3 V G a i n S e l e c t

G A I N 1 G A I N 0 G A I N

0 0 1G A I N 0 1 9 2 3 D i g i t a l I n p u t

G A I N 1 2 0 2 4 0 1 2

1 0 6 4

1 1 1 2 8

D a t a R a t e S e l e c t :

S P E E D D A T A R A T E S P E E D 2 1 2 5 D i g i t a l I n p u t

0 1 0 S P S

1 8 0 S P S

P D W N 2 2 2 6 D i g i t a l I n p u t P o w e r - D o w n : H o l d i n g t h i s p i n l o w p o w e r s d o w n t h e e n t i r e c o n v e r t e r a n d r e s e t s t h e A D C .

S e r i a l C l o c k : C l o c k o u t d a t a o n t h e r i s i n g e d g e . A l s o u s e d t o i n i t i a t e O f f s e t C a l i b r a t i o n a n d S l e e p

S C L K 2 3 2 7 D i g i t a l I n p u t m o d e s . S e e t e x t f o r m o r e d e t a i l s .

D u a l - P u r p o s e O u t p u t : D R D Y /

2 4 2 8 D i g i t a l O u t p u t D a t a R e a d y : I n d i c a t e s v a l i d d a t a b y g o i n g l o w . D O U T

D a t a O u t p u t : O u t p u t s d a t a , M S B f i r s t , o n t h e f i r s t r i s i n g e d g e o f S C L K .



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T Y P I C A L C H A R A C T E R I S T I C S

Time (Reading Number)

OutputCode(LSB)

6

5

43

2

1

1

2

3

4

5

6

200 400 600 800 10000

PGA = 1

Data Rate = 10SPS


OutputCode(LSB)

25

20

15

10

5

0

5

10

15

20

25

200 400 600 800 10000

PGA = 128

Data Rate = 10SPS

Output Code (LSB)

Occurrence

300

250

200

150

100

50

0

4 2 0 2 4

PGA = 1

Data Rate = 10SPS

Output Code (LSB)

Occurrence

100

90

80

70

60

50

40

30

20

10

0

16 16808

PGA = 128

Data Rate = 10SPS


OutputCode(LSB)

22.5

17.5

12.5

7.5

2.5

2.5

7.5

12.5

17.5

22.5200 400 600 800 10000

PGA = 1

Data Rate = 80SPS


OutputCode(LSB)

70

50

30

10

10

30

50

70

200 400 600 800 10000

PGA = 128

Data Rate = 80SPS

A D S 1 2 3 2

A D S 1 2 3 4


A t TA = + 2 5 C , A V D D = D V D D = V R E F P = 5 V , a n d V R E F N = A G N D , u n l e s s o t h e r w i s e n o t e d .

N O I S E P L O T N O I S E P L O T

F i g u r e 1 . F i g u r e 2 .

N O I S E H I S T O G R A M N O I S E H I S T O G R A M

F i g u r e 3 . F i g u r e 4 .

N O I S E P L O T N O I S E P L O T

F i g u r e 5 . F i g u r e 6 .



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Output Code (LSB)

Occurance

180

160

140

120

100

80

60

40

20

012 6 1260

PGA = 1

Data Rate = 80SPS

Output Code (LSB)

Occurance

50

45

40

35

30

25

20

15

10

5

0

40 20 0 20 40

PGA = 128

Data Rate = 80SPS

OffsetDrift(nV/ C)

-600

-500

-400

-300

-200

-100 0

100

200

300

400

500

600

35

30

25

20

15

10

5

0

Counts

PGA=1

DataRate=10SPS

90Samplesfrom3Lots

OffsetDrift(nV/ C)

-500

-400

-300

-200

-100 0

100

200

300

400

500

35

30

25

20

15

10

5

0

Counts

PGA=1

DataRate=10SPS

90Samplesfrom3Lots

GainDrift(ppm/ C)

-1

.2

-1

.1

-1

.0

-0

.9

-0

.8

-0

.7

-0

.6

-0

.5

-0

.4

-0

.3

-0

.2

-0

.1 00

.10

.20

.30

.40

.50

.60

.70

.80

.91

.01

.11

.2

18

16

14

12

10

8

6

4

2

0

Counts

PGA=1

DataRate=10SPS

90Samplesfrom3Lots

GainDrift(ppm/ C)

-1

.0

-0

.9

-0

.8

-0

.7

-0

.6

-0

.5

-0

.4

-0

.3

-0

.2

-0

.1 00

.10

.20

.30

.40

.50

.60

.70

.80

.91

.0

20

18

16

14

12

10

8

6

4

2

0

Counts

PGA=1

DataRate=10SPS

90Samplesfrom3Lots

A D S 1 2 3 2

A D S 1 2 3 4


T Y P I C A L C H A R A C T E R I S T I C S ( c o n t i n u e d )


N O I S E H I S T O G R A M N O I S E H I S T O G R A M

F i g u r e 7 . F i g u r e 8 .

O F F S E T D R I F T ( 4 0 C t o + 2 5 C ) O F F S E T D R I F T ( + 2 5 C t o + 1 0 5 C )

F i g u r e 9 . F i g u r e 1 0 .

G A I N D R I F T ( 4 0 C t o + 2 5 C ) G A I N D R I F T ( + 2 5 C t o + 1 0 5 C )

F i g u r e 1 1 . F i g u r e 1 2 .



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OffsetDrift(nV/ C)-

50

-40

-30

-20

-10 0

10

20

30

40

50

30

25

20

15

10

5

0

Counts

PGA=128

DataRate=10SPS

90Samplesfrom3Lots

OffsetDrift(nV/ C)

-30

-25

-20

-15

-10

-5 0 5

10

15

20

25

30

20

18

16

14

12

10

8

6

4

2

0

Counts

PGA=128

DataRate=10SPS

90Samplesfrom3Lots

GainDrift(ppm/ C)

0

0

.5

1

.0

1

.5

2

.0

2

.5

3

.0

3

.5

4

.0

4

.5

5

.0

25

20

15

10

5

0

Counts

PGA=128

DataRate=10SPS

90Samplesfrom3Lots

GainDrift(ppm/ C)

0

0

.5

1

.0

1

.5

2

.0

2

.5

3

.0

3

.5

4

.0

4

.5

5

.0

5

.5

6

.0

20

18

16

14

12

10

8

6

4

2

0

Counts

PGA=128

DataRate=10SPS

90Samplesfrom3Lots

Temperature (_C)

Offset(nV)

1000

500

0

500

1000

11050 30 10 10 30 50 70 90

PGA = 128

Data Rate = 10SPS

Temperature (_C)

GainError(%)

0.04

0.03

0.02

0.01

0

0.01

0.02

11050 30 10 10 30 50 70 90

PGA = 128

Data Rate = 10SPS

A D S 1 2 3 2

A D S 1 2 3 4




O F F S E T D R I F T ( 4 0 C t o + 2 5 C ) O F F S E T D R I F T ( + 2 5 C t o + 1 0 5 C )

F i g u r e 1 3 . F i g u r e 1 4 .

G A I N D R I F T ( 4 0 C t o + 2 5 C ) G A I N D R I F T ( + 2 5 C t o + 1 0 5 C )

F i g u r e 1 5 . F i g u r e 1 6 .

O F F S E T v s T E M P E R A T U R E G A I N E R R O R v s T E M P E R A T U R E

F i g u r e 1 7 . F i g u r e 1 8 .

1 0 C o p y r i g h t 2 0 0 5 2 0 0 8 , T e x a s I n s t r u m e n t s I n c o r p o r a t e d


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VIN (V)

RMSNoise(nV)

1000

900

800

700

600

500

400

300

200

100

0

2.52.5 2.0 1.5 0.51.0 1.00 0.5 1.5 2.0

PGA = 1

Data Rate = 10SPS

VIN (mV)

RMSNoise(nV)

50

45

40

35

30

25

20

15

10

5

0

1919 14.25 9.5 4.75 4.750 9.5 14.25

PGA = 128

Data Rate = 10SPS

VIN (V)

INL(ppm

ofFSR)

INL(V)

5

4

3

2

1

0

1

2

3

4

5

25

20

15

10

5

0

5

10

15

20

25

2.5

2.5

2.0

1.5

0.5

1.0 1.00 0.5 1.5 2.0

PGA = 1

VIN (mV)

INL(ppmofFSR)

INL(nV)

10

8

6

4

2

0

2

4

6

8

10

390.625

312.5

234.375

156.25

78.125

0

78.125

156.25

234.375

312.5

390.625

19

19

14.25

9.5

4.75 4.750 9.5 14.25

PGA = 128

Temperature (_C)

A

nalog

Current(A)

2000

1600

1200

800

400

0

11050 30 10 10 30 50 70 90

Normal Mode, PGA = 64, 128


Temperature (_C)

DigitalCurrent(A)

120

100

80

60

40

20

0

11050 30 10 10 30 50 70 90



Sleep Mode, All PGAs

A D S 1 2 3 2

A D S 1 2 3 4




N O I S E v s I N P U T S I G N A L N O I S E v s I N P U T S I G N A L

F i g u r e 1 9 . F i g u r e 2 0 .

I N T E G R A L N O N L I N E A R I T Y I N T E G R A L N O N L I N E A R I T Y v s I N P U T S I G N A L v s I N P U T S I G N A L

F i g u r e 2 1 . F i g u r e 2 2 .

A N A L O G C U R R E N T D I G I T A L C U R R E N T v s T E M P E R A T U R E v s T E M P E R A T U R E

F i g u r e 2 3 . F i g u r e 2 4 .

C o p y r i g h t 2 0 0 5 2 0 0 8 , T e x a s I n s t r u m e n t s I n c o r p o r a t e d 1 1


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Temperature (_C)

DataRate(SPS)

10.06

10.01

9.96

9.91

9.86

11050 30 10 10 30 50 70 90

SPEED = LOW

CLKIN/XTAL1 = LOW (Internal Oscillator)

A D S 1 2 3 2

A D S 1 2 3 4




D A T A R A T E v s T E M P E R A T U R E

F i g u r e 2 5 .



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O V E R V I E W T E M P E R A T U R E S E N S O R ( A D S 1 2 3 2 o n l y )

A N A L O G I N P U T S ( A I N P x , A I N N x )

A0A1

AINP

AINP1

AINN1

AINP2

AINN2

AINP3

AINN3

AINP4

AINN4

10I 1I

1X 8X

AINN

ADS1232 Only

AVDD

ADS1234Only

A D S 1 2 3 2

A D S 1 2 3 4


T h e A D S 1 2 3 2 a n d A D S 1 2 3 4 a r e h i g h l y i n t e g r a t e d , O n - c h i p d i o d e s p r o v i d e t e m p e r a t u r e - s e n s i n g 2 4 - b i t A D C s t h a t i n c l u d e a n i n p u t m u l t i p l e x e r , c a p a b i l i t y . B y s e t t i n g t h e T E M P p i n h i g h , t h e s e l e c t e d l o w - n o i s e P G A , t h i r d - o r d e r d e l t a - s i g m a ( ) a n a l o g i n p u t s a r e d i s c o n n e c t e d a n d t h e i n p u t s t o t h e m o d u l a t o r , a n d f o u r t h - o r d e r d i g i t a l f i l t e r . W i t h A D C a r e c o n n e c t e d t o t h e a n o d e s o f t w o d i o d e s i n p u t - r e f e r r e d R M S n o i s e d o w n t o 1 7 n V , t h e s c a l e d t o 1 x a n d 8 0 x i n c u r r e n t a n d s i z e , a s s h o w n i n

A D S 1 2 3 2 / 4 a r e i d e a l l y s u i t e d f o r m e a s u r i n g t h e v e r y F i g u r e 2 6 . B y m e a s u r i n g t h e d i f f e r e n c e i n v o l t a g e o f l o w s i g n a l s p r o d u c e d b y b r i d g e s e n s o r s i n t h e s e d i o d e s , t e m p e r a t u r e c h a n g e s c a n b e i n f e r r e d a p p l i c a t i o n s s u c h a s w e i g h s c a l e s , s t r a i n g a u g e s , a n d f r o m a b a s e l i n e t e m p e r a t u r e . T y p i c a l l y , t h e d i f f e r e n c e p r e s s u r e s e n s o r s . i n d i o d e v o l t a g e i s 1 1 1 . 7 m V a t 2 5 C w i t h a

t e m p e r a t u r e c o e f f i c i e n t o f 3 7 9 V / C . W i t h P G A = 1 C l o c k i n g c a n b e s u p p l i e d b y a n e x t e r n a l o s c i l l a t o r , a n

a n d 2 , t h e d i f f e r e n c e v o l t a g e o u t p u t f r o m t h e P G A w i l l e x t e r n a l c r y s t a l , o r b y a p r e c i s i o n i n t e r n a l o s c i l l a t o r .

b e 1 1 1 . 7 m V a n d 2 2 3 . 4 m V , r e s p e c t i v e l y . W i t h P G A = D a t a c a n b e o u t p u t a t 1 0 S P S f o r e x c e l l e n t 5 0 H z a n d

6 4 a n d 1 2 8 , i t i s i m p o s s i b l e t o u s e t h e t e m p e r a t u r e 6 0 H z r e j e c t i o n , o r a t 8 0 S P S w h e n h i g h e r s p e e d s a r e

s e n s o r f u n c t i o n . A s i m i l a r s t r u c t u r e i s u s e d i n t h e n e e d e d . T h e A D S 1 2 3 2 / 4 a r e e a s y t o c o n f i g u r e , a n d

M S C 1 2 1 0 f o r t e m p e r a t u r e m e a s u r e m e n t . F o r m o r e a l l d i g i t a l c o n t r o l i s a c c o m p l i s h e d t h r o u g h d e d i c a t e d

i n f o r m a t i o n , s e e T I a p p l i c a t i o n r e p o r t S B A A 1 0 0 ,p i n s ; t h e r e a r e n o r e g i s t e r s t o p r o g r a m . A s i m p l e

U s i n g t h e M S C 1 2 1 x a s a H i g h - P r e c i s i o n I n t e l l i g e n t t w o - w i r e s e r i a l i n t e r f a c e r e t r i e v e s t h e d a t a .

T e m p e r a t u r e S e n s o r , a v a i l a b l e f o r d o w n l o a d a t w w w . t i . c o m .

T h e i n p u t s i g n a l t o b e m e a s u r e d i s a p p l i e d t o t h e i n p u t p i n s A I N P x a n d A I N N x . T h e p o s i t i v e i n t e r n a l i n p u t i s g e n e r a l i z e d a s A I N P , a n d t h e n e g a t i v e i n t e r n a l i n p u t g e n e r a l i z e d a s A I N N . T h e s i g n a l i s s e l e c t e d t h r o u g h t h e i n p u t m u x , w h i c h i s c o n t r o l l e d b y p i n s A 0 a n d A 1 ( A D S 1 2 3 4 o n l y ) , a s s h o w n i n T a b l e 5 . F o r t h e A D S 1 2 3 2 , t h e A 1 p i n i s r e p l a c e d b y t h e T E M P p i n t o a c t i v a t e t h e o n b o a r d d i o d e s ( s e e t h e T e m p e r a t u r e S e n s o r s e c t i o n f o r m o r e d e t a i l s ) . T h e A D S 1 2 3 2 / 4 a c c e p t d i f f e r e n t i a l i n p u t s i g n a l s , b u t c a n a l s o m e a s u r e u n i p o l a r s i g n a l s . W h e n m e a s u r i n g u n i p o l a r ( o r s i n g l e - e n d e d s i g n a l s ) w i t h r e s p e c t t o g r o u n d , c o n n e c t t h e n e g a t i v e i n p u t ( A I N N x ) t o g r o u n d a n d c o n n e c t t h e i n p u t s i g n a l t o t h e p o s i t i v e i n p u t ( A I N P x ) . N o t e t h a t w h e n t h e A D S 1 2 3 2 / 4 a r e c o n f i g u r e d t h i s w a y , o n l y h a l f o f t h e c o n v e r t e r f u l l - s c a l e r a n g e i s u s e d , s i n c e o n l y p o s i t i v e d i g i t a l o u t p u t c o d e s a r e p r o d u c e d .

T a b l e 5 . I n p u t C h a n n e l S e l e c t i o n w i t h A 0 a n d A 1 ( A D S 1 2 3 4 o n l y )

M U X P I N S S E L E C T E D A N A L O G I N P U T S

A 1 A 0 P O S I T I V E I N P U T N E G A T I V E I N P U T

0 0 A I N P 1 A I N N 1

0 1 A I N P 2 A I N N 2

1 0 A I N P 3 A I N N 3 1 1 A I N P 4 A I N N 3

F i g u r e 2 6 . M e a s u r e m e n t o f t h e T e m p e r a t u r e S e n s o r i n t h e I n p u t M u l t i p l e x e r


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B y p a s s C a p a c i t o r L O W - N O I S E P G A

V O L T A G E R E F E R E N C E I N P U T S

ZEFF+1

2fMODCBUF

RINT

RINT

RF1

R1 RF2ADCA3

Gainof1or2

CAP

AINP

AINN

CAP

A2

A1

450W

18pF

450W

18pF

A D S 1 2 3 2

A D S 1 2 3 4


B y a p p l y i n g a 0 . 1 F e x t e r n a l c a p a c i t o r ( C E X T) a c r o s s T h e A D S 1 2 3 2 / 4 f e a t u r e s a l o w - d r i f t , l o w - n o i s e P G A t w o c a p a c i t o r p i n s a n d t h e c o m b i n a t i o n o f t h e i n t e r n a l t h a t p r o v i d e s a c o m p l e t e f r o n t - e n d s o l u t i o n f o r b r i d g e 2 k r e s i s t o r R I N T o n - c h i p , a l o w - p a s s f i l t e r ( w i t h a s e n s o r s . A s i m p l i f i e d d i a g r a m o f t h e P G A i s s h o w n i n c o r n e r f r e q u e n c y o f 7 2 0 H z ) i s c r e a t e d t o b a n d l i m i t t h e F i g u r e 2 7 . I t c o n s i s t s o f t w o c h o p p e r - s t a b i l i z e d s i g n a l p a t h p r i o r t o t h e m o d u l a t o r i n p u t . T h i s l o w - p a s s a m p l i f i e r s ( A 1 a n d A 2 ) a n d t h r e e a c c u r a t e l y - m a t c h e d

f i l t e r s e r v e s t w o p u r p o s e s . F i r s t , t h e i n p u t s i g n a l i s r e s i s t o r s ( R 1 , RF 1 , a n d R F 2) , w h i c h c o n s t r u c t a b a n d l i m i t e d t o p r e v e n t a l i a s i n g a s w e l l a s t o f i l t e r o u t d i f f e r e n t i a l f r o n t - e n d s t a g e w i t h a g a i n o f 6 4 , f o l l o w e d t h e h i g h - f r e q u e n c y n o i s e . S e c o n d , i t a t t e n u a t e s t h e b y g a i n s t a g e A 3 . T h e P G A i n p u t s a r e e q u i p p e d w i t h c h o p p i n g r e s i d u e f r o m t h e P G A ( f o r g a i n s o f 6 4 a n d a n E M I f i l t e r , a s s h o w n i n F i g u r e 2 7 . T h e c u t - o f f 1 2 8 o n l y ) t o i m p r o v e t e m p e r a t u r e d r i f t p e r f o r m a n c e . I t f r e q u e n c y o f t h e E M I f i l t e r i s 1 9 . 6 M H z . I f t h e P G A i s i s n o t r e q u i r e d t o u s e h i g h q u a l i t y c a p a c i t o r s ( s u c h a s s e t t o 1 o r 2 , t h e g a i n - o f - 6 4 s t a g e i s b y p a s s e d a n d c e r a m i c o r t a n t a l u m c a p a c i t o r s ) f o r a g e n e r a l s h u t d o w n t o s a v e p o w e r . W i t h t h e c o m b i n a t i o n o f a p p l i c a t i o n . H o w e v e r , h i g h q u a l i t y c a p a c i t o r s s u c h a s b o t h g a i n s t a g e s , t h e P G A c a n b e s e t t o 6 4 o r 1 2 8 . p o l y a r e r e c o m m e n d e d f o r h i g h l i n e a r i t y a p p l i c a t i o n s . T h e P G A o f t h e A D S 1 2 3 2 / 4 c a n b e s e t t o 1 , 2 , 6 4 , o r

1 2 8 w i t h p i n s G A I N 1 ( M S B ) a n d G A I N 0 ( L S B ) . B y u s i n g A V D D a s t h e r e f e r e n c e i n p u t , t h e b i p o l a r i n p u t r a n g e s f r o m 2 . 5 V t o 1 9 . 5 m V , w h i l e t h e u n i p o l a r ( R E F P , R E F N ) r a n g e s f r o m 2 . 5 V t o 1 9 . 5 m V . W h e n t h e P G A i s s e t t o

T h e v o l t a g e r e f e r e n c e u s e d b y t h e m o d u l a t o r i s 1 o r 2 , t h e a b s o l u t e i n p u t s c a n g o r a i l - t o - r a i l w i t h o u t

g e n e r a t e d f r o m t h e v o l t a g e d i f f e r e n c e b e t w e e n R E F P s i g n i f i c a n t p e r f o r m a n c e d e g r a d a t i o n . H o w e v e r , t h e a n d R E F N : V R E F = R E F P R E F N . T h e r e f e r e n c e i n p u t s o f t h e A D S 1 2 3 2 / 4 a r e p r o t e c t e d w i t h i n t e r n a l i n p u t s u s e a s t r u c t u r e s i m i l a r t o t h a t o f t h e a n a l o g

d i o d e s c o n n e c t e d t o t h e p o w e r - s u p p l y r a i l s . T h e s e i n p u t s . I n o r d e r t o i n c r e a s e t h e r e f e r e n c e i n p u t

d i o d e s w i l l c l a m p t h e a p p l i e d s i g n a l t o p r e v e n t i t f r o m i m p e d a n c e , a s w i t c h i n g b u f f e r c i r c u i t r y i s u s e d t o

d a m a g i n g t h e i n p u t c i r c u i t r y . O n t h e o t h e r h a n d , w h e n r e d u c e t h e i n p u t e q u i v a l e n t c a p a c i t a n c e . T h e

t h e P G A i s s e t t o 6 4 o r 1 2 8 , t h e o p e r a t i n g i n p u t r a n g e r e f e r e n c e d r i f t a n d n o i s e i m p a c t A D C p e r f o r m a n c e . I n

i s l i m i t e d t o ( A G N D + 1 . 5 V ) t o ( A V D D 1 . 5 V ) , i n o r d e r t o a c h i e v e b e s t r e s u l t s , p a y c l o s e a t t e n t i o n t o

o r d e r t o p r e v e n t s a t u r a t i n g t h e d i f f e r e n t i a l f r o n t - e n d t h e r e f e r e n c e n o i s e a n d d r i f t s p e c i f i c a t i o n s . A

c i r c u i t r y a n d d e g r a d i n g p e r f o r m a n c e . s i m p l i f i e d d i a g r a m o f t h e c i r c u i t r y o n t h e r e f e r e n c e i n p u t s i s s h o w n i n F i g u r e 2 8 . T h e s w i t c h e s a n d c a p a c i t o r s c a n b e m o d e l e d w i t h a n e f f e c t i v e i m p e d a n c e o f :

W h e r e :

fM O D = m o d u l a t o r s a m p l i n g f r e q u e n c y ( 7 6 . 8 k H z )

CB U F = i n p u t c a p a c i t a n c e o f t h e b u f f e r

F o r t h e A D S 1 2 3 2 / 4 :

F i g u r e 2 7 . S i m p l i f i e d D i a g r a m o f t h e P G A



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ZEFF+1

(2)(76.8kHz)(13fF)+ 500MW

CLK_DETECT

Internal

Oscillator

MUX

ToADC

SS0 S1

EN

Crystal

OscillatorCLKIN/XTAL1

XTAL2

AVDD

(1) fMOD = 76.8kHz

ZEFF = 500M(1)

VREFP VREFN

AVDD

ESD

Protection

CBUF

C L O C K S O U R C E S

A D S 1 2 3 2

A D S 1 2 3 4


F i g u r e 2 9 . E q u i v a l e n t C i r c u i t r y o f t h e C l o c k S o u r c e

W h e n t h e c l o c k s o u r c e i s a c r y s t a l , s i m p l y c o n n e c t t h e 4 . 9 1 5 2 M H z c r y s t a l a c r o s s t h e C L K I N / X T A L 1 a n d X T A L 2 p i n s . T a b l e 6 s h o w s t h e r e c o m m e n d e d p a r t n u m b e r s . D u e t o t h e l o w - p o w e r d e s i g n o f t h e p a r a l l e l r e s o n a n t d r i v e r c i r c u i t r y o n b o a r d , b o t h t h e

F i g u r e 2 8 . S i m p l i f i e d R e f e r e n c e I n p u t C i r c u i t r y C L K I N / X T A L 1 a n d X T A L 2 p i n s a r e o n l y f o r u s e w i t h

e x t e r n a l c r y s t a l s ; t h e y s h o u l d n o t b e u s e d a s c l o c k o u t p u t d r i v e r s f o r e x t e r n a l c i r c u i t r y . N o e x t e r n a l E S D d i o d e s p r o t e c t t h e r e f e r e n c e i n p u t s . T o p r e v e n t c a p a c i t o r s a r e u s e d w i t h t h e c r y s t a l ; i t i s t h e s e d i o d e s f r o m t u r n i n g o n , m a k e s u r e t h e v o l t a g e s r e c o m m e n d e d t o p l a c e t h e c r y s t a l c l o s e t o t h e p a r t i n o n t h e r e f e r e n c e p i n s d o n o t g o b e l o w G N D b y m o r e o r d e r t o r e d u c e b o a r d s t r a y c a p a c i t a n c e f o r b o t h t h e t h a n 1 0 0 m V , a n d l i k e w i s e , d o n o t e x c e e d A V D D b y C L K I N / X T A L 1 a n d X T A L 2 p i n s a n d t o i n s u r e p r o p e r 1 0 0 m V : o p e r a t i o n .

G N D 1 0 0 m V < ( R E F P o r R E F N ) < A V D D + 1 0 0 m V

T a b l e 6 . R e c o m m e n d e d C r y s t a l s

M A N U F A C T U R E R F R E Q U E N C Y P A R T N U M B E R

T h e A D S 1 2 3 2 / 4 c a n u s e a n e x t e r n a l c l o c k s o u r c e , E C S 4 . 9 1 5 2 M H z E C S - 4 9 - 2 0 - 1 e x t e r n a l c r y s t a l , o r i n t e r n a l o s c i l l a t o r t o a c c o m m o d a t e

E C S 4 . 9 1 5 2 M H z E C S - 4 9 - 2 0 - 4 a w i d e v a r i e t y o f a p p l i c a t i o n s . F i g u r e 2 9 s h o w s t h e

e q u i v a l e n t c i r c u i t r y o f t h e c l o c k s o u r c e . T h e C L K _ D E T E C T b l o c k d e t e r m i n e s w h e t h e r t h e c r y s t a l A n e x t e r n a l o s c i l l a t o r m a y b e u s e d b y d r i v i n g t h e o s c i l l a t o r / e x t e r n a l c l o c k s i g n a l i s a p p l i e d t o t h e C L K I N / X T A L 1 p i n d i r e c t l y . T h e E l e c t r i c a l C L K I N / X T A L 1 p i n s o t h a t t h e i n t e r n a l o s c i l l a t o r i s C h a r a c t e r i s t i c s t a b l e s h o w s t h e a l l o w a b l e f r e q u e n c y b y p a s s e d o r a c t i v a t e d . W h e n t h e C L K I N / X T A L 1 p i n r a n g e . f r e q u e n c y i s a b o v e ~ 2 0 0 k H z , t h e C L K _ D E T E C T

o u t p u t g o e s l o w a n d s h u t s d o w n t h e i n t e r n a l o s c i l l a t o r . W h e n t h e X I N p i n f r e q u e n c y i s b e l o w ~ 2 0 0 k H z , t h e C L K _ D E T E C T o u t p u t g o e s h i g h a n d a c t i v a t e s t h e i n t e r n a l o s c i l l a t o r . I t i s h i g h l y r e c o m m e n d e d t o h a r d - w i r e t h e C L K I N / X T A L 1 p i n t o g r o u n d w h e n t h e i n t e r n a l o s c i l l a t o r i s c h o s e n .



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F R E Q U E N C Y R E S P O N S E

Frequency (kHz)

Gain(dB)

0

20

40

60

80

100

120

140

160

180

200

38.4 76.80

fCLK = 4.9152MHz

Frequency (Hz)

Gain(dB)

0

50

100

150

0 10 20 30 40 50 60 70 80 90 100

(a)

Frequency (Hz)

(b)

Gain(dB)

50

100

150

494846 47 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64

Data Rate = 10SPS

Data Rate = 10SPS

A D S 1 2 3 2

A D S 1 2 3 4


F i g u r e 3 1 ( b ) s h o w s t h e z o o m i n p l o t f o r b o t h 5 0 H z a n d 6 0 H z n o t c h e s w i t h t h e S P E E D p i n t i e d l o w

T h e A D S 1 2 3 2 / 4 u s e a s i n c 4 d i g i t a l f i l t e r w i t h t h e ( 1 0 S P S d a t a r a t e ) . W i t h o n l y a 3 % v a r i a t i o n o f t h e

f r e q u e n c y r e s p o n s e ( f C L K = 4 . 9 1 5 2 M H z ) s h o w n i n i n t e r n a l o s c i l l a t o r , o v e r 1 0 0 d B o f n o r m a l - m o d e F i g u r e 3 0 . T h e f r e q u e n c y r e s p o n s e r e p e a t s a t

r e j e c t i o n i s a c h i e v e d . m u l t i p l e s o f t h e m o d u l a t o r s a m p l i n g f r e q u e n c y o f 7 6 . 8 k H z . T h e o v e r a l l r e s p o n s e i s t h a t o f a l o w - p a s s

f i l t e r w i t h a 3 d B c u t o f f f r e q u e n c y o f 3 . 3 2 H z w i t h t h e S P E E D p i n t i e d l o w ( 1 0 S P S d a t a r a t e ) a n d 1 1 . 6 4 H z w i t h t h e S P E E D p i n t i e d h i g h ( 8 0 S P S d a t a r a t e ) .

F i g u r e 3 0 . F r e q u e n c y R e s p o n s e

T o h e l p s e e t h e r e s p o n s e a t l o w e r f r e q u e n c i e s , F i g u r e 3 1 ( a ) i l l u s t r a t e s t h e r e s p o n s e o u t t o 1 0 0 H z , w h e n t h e d a t a r a t e = 1 0 S P S . N o t i c e t h a t s i g n a l s a t m u l t i p l e s o f 1 0 H z a r e r e j e c t e d , a n d t h e r e f o r e s i m u l t a n e o u s r e j e c t i o n o f 5 0 H z a n d 6 0 H z i s a c h i e v e d .

T h e b e n e f i t o f u s i n g a s i n c 4 f i l t e r i s t h a t e v e r y F i g u r e 3 1 . F r e q u e n c y R e s p o n s e O u t T o 1 0 0 H z f r e q u e n c y n o t c h h a s f o u r z e r o s o n t h e s a m e l o c a t i o n .

T h i s r e s p o n s e , c o m b i n e d w i t h t h e l o w d r i f t i n t e r n a l o s c i l l a t o r , p r o v i d e s a n e x c e l l e n t n o r m a l - m o d e T h e A D S 1 2 3 2 / 4 d a t a r a t e a n d f r e q u e n c y r e s p o n s e r e j e c t i o n o f l i n e - c y c l e i n t e r f e r e n c e . s c a l e d i r e c t l y w i t h c l o c k f r e q u e n c y . F o r e x a m p l e , i f

fC L K i n c r e a s e s f r o m 4 . 9 1 5 2 M H z t o 6 . 1 4 4 M H z w h e n t h e S P E E D p i n i s t i e d h i g h , t h e d a t a r a t e i n c r e a s e s f r o m 8 0 S P S t o 1 0 0 S P S , w h i l e n o t c h e s a l s o i n c r e a s e f r o m 8 0 H z t o 1 0 0 H z . N o t e t h a t t h i s i s o n l y p o s s i b l e w h e n t h e e x t e r n a l c l o c k s o u r c e i s a p p l i e d .



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S E T T L I N G T I M E

A1orA0

t1

DRDY/DOUT

tS

ToggledTEMPPinor AbruptChangeinExternalVIN

VIN

DRDY/DOUT

Startof

conversion.

1stconversion;

includes

unsettledV .IN

2ndconversion;

V settled,butINdigitalfilter

unsettled.

3rdconversion;


unsettled.

4thconversion;


unsettled.

5thconversion;

V anddigitalINfilterboth

settled.

Conversion

Time

A D S 1 2 3 2

A D S 1 2 3 4


s w i t c h i n g i n p u t c h a n n e l s . A n o t h e r e x a m p l e w o u l d b e t o g g l i n g t h e T E M P p i n , w h i c h s w i t c h e s t h e i n t e r n a l

A f t e r c h a n g i n g t h e i n p u t m u l t i p l e x e r , t h e f i r s t d a t a a r e A I N P , A I N N s i g n a l s t o c o n n e c t t o e i t h e r t h e e x t e r n a l

f u l l y s e t t l e d . I n b o t h t h e A D S 1 2 3 2 / 4 , t h e d i g i t a l f i l t e r i s A I N P x , A I N N x p i n s o r t o t h e T E M P d i o d e ( s e e

a l l o w e d t o s e t t l e a f t e r t o g g l i n g e i t h e r t h e A 1 o r A 0 p i n . F i g u r e 2 6 ) .

T o g g l i n g a n y o f t h e s e d i g i t a l p i n s w i l l h o l d t h e D R D Y / D O U T l i n e h i g h u n t i l t h e d i g i t a l f i l t e r i s f u l l y N o t e t h a t w h e n s e t t l i n g d a t a , f i v e r e a d i n g s m a y b e

s e t t l e d . F o r e x a m p l e , i f A 0 c h a n g e s f r o m l o w t o h i g h , r e q u i r e d . I f t h e c h a n g e i n i n p u t o c c u r s i n t h e m i d d l e s e l e c t i n g a d i f f e r e n t i n p u t c h a n n e l , D R D Y / D O U T o f t h e f i r s t c o n v e r s i o n , f o u r m o r e f u l l c o n v e r s i o n s o f i m m e d i a t e l y g o e s h i g h , a n d D R D Y / D O U T g o e s l o w t h e f u l l y - s e t t l e d i n p u t a r e r e q u i r e d t o g e t f u l l y - s e t t l e d w h e n f u l l y - s e t t l e d d a t a a r e r e a d y f o r r e t r i e v a l . T h e r e d a t a . D i s c a r d t h e f i r s t f o u r r e a d i n g s b e c a u s e t h e y i s n o n e e d t o d i s c a r d a n y d a t a . F i g u r e 3 2 s h o w s t h e c o n t a i n o n l y p a r t i a l l y - s e t t l e d d a t a . F i g u r e 3 3 i l l u s t r a t e s t i m i n g o f t h e D R D Y / D O U T l i n e a s t h e i n p u t t h e s e t t l i n g t i m e f o r t h e A D S 1 2 3 2 / 4 i n C o n t i n u o u s m u l t i p l e x e r c h a n g e s . C o n v e r s i o n m o d e .

I n c e r t a i n i n s t a n c e s , l a r g e a n d / o r a b r u p t c h a n g e s i n i n p u t w i l l r e q u i r e f o u r d a t a c y c l e s t o s e t t l e . O n e e x a m p l e o f s u c h a c h a n g e w o u l d b e a n e x t e r n a l m u l t i p l e x e r i n f r o n t o f t h e A D S 1 2 3 2 / 4 , w h i c h c a n c a u s e l a r g e c h a n g e s i n i n p u t v o l t a g e s i m p l y b y

F i g u r e 3 2 . E x a m p l e o f S e t t l i n g T i m e A f t e r C h a n g i n g t h e I n p u t M u l t i p l e x e r

S Y M B O L D E S C R I P T I O N ( 1 ) M I N M A X U N I T S

tS S e t u p t i m e f o r c h a n g i n g t h e A 1 o r A 0 p i n s 4 0 5 0 s

S P E E D = 1 5 1 5 1 m s S e t t l i n g t i m e ( D R D Y / D O U T t1 h e l d h i g h ) S P E E D = 0 4 0 1 4 0 1 m s

( 1 ) V a l u e s g i v e n f o r f C L K = 4 . 9 1 5 2 M H z . F o r d i f f e r e n t f C L K f r e q u e n c i e s , s c a l e p r o p o r t i o n a l t o C L K p e r i o d . E x p e c t a 3 % v a r i a t i o n w h e n a n i n t e r n a l o s c i l l a t o r i s u s e d .

F i g u r e 3 3 . S e t t l i n g T i m e i n C o n t i n u o u s C o n v e r s i o n M o d e


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D A T A R A T E D A T A R E A D Y / D A T A O U T P U T ( D R D Y / D O U T )

S E R I A L C L O C K I N P U T ( S C L K )

D A T A F O R M A T

A D S 1 2 3 2

A D S 1 2 3 4


T h e A D S 1 2 3 2 / 4 d a t a r a t e i s s e t b y t h e S P E E D p i n , T h i s d i g i t a l o u t p u t p i n s e r v e s t w o p u r p o s e s . F i r s t , i t a s s h o w n i n T a b l e 7 . W h e n S P E E D i s l o w , t h e d a t a i n d i c a t e s w h e n n e w d a t a a r e r e a d y b y g o i n g l o w . r a t e i s n o m i n a l l y 1 0 S P S . T h i s d a t a r a t e p r o v i d e s t h e A f t e r w a r d s , o n t h e f i r s t r i s i n g e d g e o f S C L K , t h e l o w e s t n o i s e , a n d a l s o h a s e x c e l l e n t r e j e c t i o n o f b o t h D R D Y / D O U T p i n c h a n g e s f u n c t i o n a n d b e g i n s 5 0 H z a n d 6 0 H z l i n e - c y c l e i n t e r f e r e n c e . F o r o u t p u t t i n g t h e c o n v e r s i o n d a t a , m o s t s i g n i f i c a n t b i t

a p p l i c a t i o n s r e q u i r i n g f a s t d a t a r a t e s , s e t t i n g S P E E D ( M S B ) f i r s t . D a t a a r e s h i f t e d o u t o n e a c h s u b s e q u e n t h i g h s e l e c t s a d a t a r a t e o f n o m i n a l l y 8 0 S P S . S C L K r i s i n g e d g e . A f t e r a l l 2 4 b i t s h a v e b e e n

r e t r i e v e d , t h e p i n c a n b e f o r c e d h i g h w i t h a n T a b l e 7 . D a t a R a t e S e t t i n g s a d d i t i o n a l S C L K . I t w i l l t h e n s t a y h i g h u n t i l n e w d a t a

a r e r e a d y . T h i s c o n f i g u r a t i o n i s u s e f u l w h e n p o l l i n g D A T A R A T E

o n t h e s t a t u s o f D R D Y / D O U T t o d e t e r m i n e w h e n t o S P E E D I n t e r n a l O s c i l l a t o r E x t e r n a l b e g i n d a t a r e t r i e v a l .

P I N o r 4 . 9 1 5 2 M H z C r y s t a l O s c i l l a t o r

0 1 0 S P S f C L K I N / 4 9 1 , 5 2 0

1 8 0 S P S f C L K I N / 6 1 , 4 4 0 T h i s d i g i t a l i n p u t s h i f t s s e r i a l d a t a o u t w i t h e a c h r i s i n g e d g e . T h i s i n p u t h a s b u i l t - i n h y s t e r e s i s , b u t c a r e s h o u l d s t i l l b e t a k e n t o e n s u r e a c l e a n s i g n a l . G l i t c h e s o r s l o w - r i s i n g s i g n a l s c a n c a u s e u n w a n t e d a d d i t i o

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