Datasheet

LTC1272
20
1272fc
For more information www.linear.com/1272
APPLICATIONS INFORMATION
Figure 23. Plugging the LTC1272 into an AD7572 Socket
Case 2: Clock Not Synchronous with CS and RD
EXTERNAL
ASYNCHRONOUS
CLOCK
10µF
IN
REF
D11 (MSB)
D10
D9
D8
D7
CLK IN
CLK OUT
HBEN
RD
CS
BUSY
NC
V
LTC1272
D6
D5
D4
DGND
D3/11
D2/10
D1/9
D0/8
A
V
AGND
DD
µP
CONTROL
LINES
0.1µF
–15V
µP
DATA
BUS
ANALOG INPUT
(0V TO 5V)
10µF
THE LTC1272 HAS THE SAME 0V TO 5V INPUT RANGE BUT PROVIDES A 2.42V
REFERENCE OUTPUT AS OPPOSED TO THE –5.25V OF THE AD7572. FOR PROPER
OPERATION, REVERSE THE REFERENCE CAPACITOR POLARITY AND SHORT OUT THE
10Ω RESISTOR.
*
THE D FLIP-FLOP SYNCHRONIZES THE CONVERSION START SIGNAL (RD ) TO THE
ADC CLK SIGNAL TO PREVENT OUTPUT CODE NOISE WHICH OCCURS WITH
AN ASYNCHRONOUS CLOCK.
**
THE LTC1272 CAN ACCOMMODATE THE –15V SUPPLY OF THE AD7572 BUT DOES
NOT REQUIRE IT. PIN 23 OF THE LTC1272 IS NOT INTERNALLY CONNECTED.
LTC1272 • F23
2.42V
V
OUTPUT
*
REF
10Ω*
0.1µF
+
10µF
0.1µF
5V
+
OUT
74HC04
RD
S
Q
D**
CLK
1/2
74HC74
OR
+