COMBOSMARTMETER datasheet(18/60 Pages) TI1

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PgaP

(for Gain = 2)

60 kΩ

From MuxP

PgaN

From MuxN

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 k

Ω 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)

237

146

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COMBOSMARTMETER 数据表(PDF) 18 Page - Texas Instruments