Datasheet

MAX9939
SPI Programmable-Gain Amplifier
with Input V
OS
Trim and Output Op Amp
10
Maxim Integrated
Differential-Input, Differential-Output PGA
The output amplifier can be configured so that the
MAX9939 operates as a differential-input, differential-
output programmable gain amplifier. As shown in
Figure 4, use a 10kΩ resistor between OUTA and INB,
and between INB and OUTB. Such a differential-output
configuration is ideal for use in low-voltage applications
that can benefit from the 2X output voltage dynamic
range when compared to single-ended output format.
Use of Output Operational Amplifier as TIA
CMOS inputs on the output op amp makes it ideal for
use as an input transimpedance amplifier (TIA) in cer-
tain current-output sensor applications. In such a situ-
ation, keep in mind that the inverting input operates at
fixed voltage of V
CC
/2. Use a high-value resistor as a
feedback gain element, and use a feedback capacitor
in parallel with this resistor if necessary to aid amplifi-
er stability in the presence of high photodiode or
cable capacitance. The output of this TIA can be rout-
ed to INA+ or INA- for further processing and signal
amplification.
Power-Supply Bypassing
Bypass V
CC
to GND with a 0.1µF capacitor in parallel
with a 1µF low-ESR capacitor placed as close as possi-
ble to the MAX9939.
INPUT OFFSET VOLTAGE
(V4 = 0 TRIMS POSITIVE, V4 = 1 TRIMS NEGATIVE)
V3:V0 V
OS
(mV)
0000 0
0001 1.3
0010 2.5
0011 3.8
0100 4.9
0101 6.1
0110 7.3
0111 8.4
1000 10.6
1001 11.7
1010 12.7
1011 13.7
1100 14.7
1101 15.7
1110 16.7
1111 17.6
Table 4. Input Offset-Voltage Trim