Datasheet

ADS931
11
SBAS060A
1kΩ
1kΩ
LpBy
REFT
REFB
LnBy
+V
S
IN
CM
R
T
4kΩ
1kΩ
R
B
4kΩ
1kΩ
0.1µF
0.1µF
0.1µF
0.1µF
0.1µF
+3V
2kΩ
V
IN
+V
S
R
T
R
B
REFT REFB
ADS931
0.1µF
+1.5V
0.1µF10µF
3V
5V
5V
5V
4kΩ
12kΩ
8kΩ
3kΩ
4kΩ
12kΩ
8kΩ
3kΩ
2V
2V
3V
3.5V
1V
1V
2V
1.5V
reference voltage is established by a two terminal bandgap
reference diode, the REF1004-1.2. Using a general-purpose
single-supply dual operational amplifier (A
1
), like an
OPA2237, OPA2234 or MC34072, the two required refer-
ence voltages for the ADS931 can be generated by setting
each op amp to the appropriate gain; for example: set REFT
to +2V and REFB to +1V.
CLOCK INPUT
The clock input of the ADS931 is designed to accommodate
either +3V or +5V CMOS logic levels. To drive the clock
input with a minimum amount of duty cycle variation and
support the maximum sampling rate (30MSPS), high speed
or advanced CMOS logic should be used (HC/HCT,
AC/ACT). When digitizing at high sampling rates, a 50%
FIGURE 7. High Accuracy Solution to Supply External Reference Voltages.
1/2 A
1
R
F1
R
G1
3kΩ
5kΩ
REF1004
+1.2V
10kΩ
10Ω
Top
Reference
+V
S
+V
S
1/2 A
1
R
F2
R
G2
10Ω
Bottom
Reference
FIGURE 6. Low-cost Solution to Supply External Reference Voltages.