TPS7A39
www.ti.com.cn
ZHCSGP0A –JULY 2017–REVISED SEPTEMBER 2017
8.2.2 Design 2: Getting the Full Range of a SAR ADC
OUTP
FBP
VOUTP = 5.2 V
COUTP
INP
CINP
CFFP
R1P
+
6 V
œ
R2P
NR/SS
CNR/SS
TPS7A39
BUF
FBN
3mm x 3mm
R1N
+
3.3 V
œ
CFFN
EN
R2N
VOUTN = -0.2 V
OUTN
INN
CINN
COUTN
GND
1 nF
1 kΩ
1 kΩ
Positive
Differential Input
VOUTP
œ
2.2 Ω
AINP
OPA625
+
10 nF
VOUTN
+
Vin
œ
OPA625_CM
ADC
10 nF
10 nF
VOUTP
+
OPA625
AINN
Negative
Differential Input
2.2 Ω
œ
VOUTN
1 kΩ
1 kΩ
1 nF
图 78. Creating Power Rails for an Analog Front-End of an ADC
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