Datasheet

10kW
ADC
G=1
R
F
R
I
Output
Stage
SPI
Interface
REF3225
SCLK
DIO
CS
V
OUT
DV
DD
AV
DD
GND
V
REF
MSP430
Microcontroller
+3V
+3V
V
REF
PGA112
PGA113
V /CH0
CAL
CH1
CAL3
CAL4
CAL1
CAL2
0.1V
CAL
0.9V
CAL
10kW
80kW
MUX
CAL2/3
2.5V
ADCRef
C
0.1 F
BYPASS
m
C
0.1 F
BYPASS
m
C
0.1 F
BYPASS
m
PGA112 , , PGA113
PGA116 , PGA117
SBOS424B – MARCH 2008 – REVISED SEPTEMBER 2008 ............................................................................................................................................ www.ti.com
Figure 73. Using CAL Channels with V
REF
= Ground
Table 9. Using the MUX CAL Channels with V
REF
= GND
(AV
DD
= 3V, DV
DD
= 3V, ADC Ref = 2.5V, and V
REF
= GND)
MUX GAIN OP AMP OP AMP
FUNCTION SELECT SELECT MUX INPUT (+In) (V
OUT
) DESCRIPTION
Minimum signal level that the
MUX, op amp, and ADC can
Minimum Signal CAL1 1 GND GND 50mV
read. Op amp V
OUT
is limited
by negative saturation.
90% ADC Ref for system
0.9 ×
Gain Calibration CAL2 1 2.25V 2.25V full-scale or gain calibration
(V
CAL
/CH0)
of the ADC.
Maximum signal level that
the MUX, op amp, and ADC
can read. Op amp V
OUT
is
0.9 ×
Maximum Signal CAL2 2 2.25V 2.95V limited by positive saturation.
(V
CAL
/CH0)
System is limited by ADC
max input of 2.5V (ADC Ref
= 2.5V).
0.1 × 10% ADC Ref for system
Offset Calibration CAL3 1 0.25V 0.25V
(V
CAL
/CH0) offset calibration of the ADC.
Minimum signal level that the
MUX, op amp, and ADC can
Minimum Signal CAL4 1 V
REF
GND 50mV
read. Op amp V
OUT
is limited
by negative saturation.
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