Datasheet

PgaP
R2
(for Gain = 2)
60 kΩ
From MuxP
PgaN
From MuxN
R2
R1
30 kΩ
30 kΩ
To ADC
ADS131E04
ADS131E06
ADS131E08
SBAS561A –JUNE 2012–REVISED APRIL 2013 www.ti.com
PGA SETTINGS AND INPUT RANGE
The PGA is a differential input and output amplifier, as shown in Figure 21. It has five gain settings (1, 2, 4, 8,
and 12) that can be set by writing to the CHnSET register (see the CHnSET Register in the Register Map section
for details). The ADS131E0x have CMOS inputs and therefore have negligible current noise. Table 3 shows the
typical bandwidth values for various gain settings. Note that Table 3 shows small-signal bandwidth. For large
signals, performance is limited by PGA slew rate.
The PGA resistor string that implements the gain has 120 kΩ of resistance for a gain of 2. This resistance
provides a current path across the PGA outputs in the presence of a differential input signal. This current is in
addition to the quiescent current specified for the device in the presence of a differential signal at the input.
Figure 21. PGA Implementation
Table 3. PGA Gain versus Bandwidth
GAIN NOMINAL BANDWIDTH AT ROOM TEMPERATURE (kHz)
1 237
2 146
4 96
8 48
12 32
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