SP574B/674B/1674B/774B

12–Bit Sampling A/D Converters

© Copyright 2000 Sipex Corporation

10

A

verter at any time. Break–before–make action is

guaranteed between the two data bytes. This as-

sures that the outputs which are strapped together

in Figure 5 will never be enabled at the same time.

In Figure 7, it can be seen that a read operation

usually begins after the conversion is complete and

STS is low. If earlier access is needed, the read can

begin no later than the addition of times t

before STS goes low.

"NYQUIST" SAMPLING

Each of the SPx74B analog-to-digital convert-

ers has been designed to provide Nyquist sam-

pling (highest input frequency is 1/2 of the

sampling rate) data conversion with no degra-

dation in DC performance. This is shown in

Figure 10. Note that the Differential Linearity

and Integral Linearity min/max values are well

within the

± 1/2 LSB limits of a K-version

Converter. Also, the Typical FFT at Nyquist

rates shown on Figure 10 reflect the values

listed in the Typical AC Dynamics table.

STS

DELAY

R

CK

Q

D

H

D

CK

Q

Q

EOC8

EOC12

CE

R/C

A0

CS

12/8

READ CONTROL

A0 LATCH

INPUT BUFFERS

NIBBLE B ZERO

OVERRIDE

NIBBLE A, B

NIBBLE C

Figure 4. SPx74B Control Logic

28

27

26

25

24

23

22

21

20

19

18

17

16

15

STS

DB11 (MSB)

DB0 (LSB)

DIG

COM

SPx74B

2

4

A0

ADDRESS BUS

A0

12/8

DATA

BUS

Figure 5. Interfacing SPx74B to 8–Bit Interface Bus