ADS1294CZXGR datasheet(31/114 Pages) TI2

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PGAp

50k

20k

(for Gain = 6)

50k

From MuxP

PGAn

From MuxN

To ADC

ADS1294, ADS1294R, ADS1296, ADS1296R, ADS1298, ADS1298R

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SBAS459K – JANUARY 2010 – REVISED AUGUST 2015

9.3.1.5 PGA Settings and Input Range

The PGA is a differential input and differential output amplifier, as shown in Figure 29. The PGA has seven gain

settings (1, 2, 3, 4, 6, 8, and 12) that are set by writing to the CHnSET register (see the CHnSET: Individual

Channel Settings (n = 1 to 8) (address = 05h to 0Ch) (reset = 00h) section). The ADS129x have CMOS inputs,

and therefore have negligible current noise. Table 5 shows the typical values of bandwidths for various gain

settings. Table 5 shows the small-signal bandwidth.

Figure 29. PGA Implementation

Table 5. PGA Gain versus Small-Signal Bandwidth

NOMINAL BANDWIDTH AT ROOM

GAIN

TEMPERATURE (kHz)

237

146

127

The resistor string of the PGA that implements the gain has 120 k

Ω of resistance for a gain of 6. This resistance

provides a current path across the outputs of the PGA 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.

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ADS1294CZXGR Datasheet(PDF) 31 Page - Texas Instruments