ADS1291IPBS datasheet(36/83 Pages) TI2

36 / 83 page

400 k

150 k

RLD1P

400 k

60 k

RLD1N

400 k

150 k

RLD2P

60 k

400 k

RLD2N

From

MUX1P

From

MUX2P

From

MUX2N

From

MUX1N

RLDOUT

1 M

EXT

(1)

EXT

(1)

1.5 nF

RLDREF_INT

RLD

Amp

RLDINV

RLDIN/RLDREF

RLDREF_INT

PGA1P

PGA1N

PGA2N

PGA2P

To MUX

(AVDD + AVSS)

ADS1291, ADS1292, ADS1292R

SBAS502C – DECEMBER 2011 – REVISED APRIL 2020

www.ti.com

Product Folder Links: ADS1291 ADS1292 ADS1292R

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8.3.10.2.4

Right Leg Drive (RLD DC Bias Circuit)

The right leg drive (RLD) circuitry is used as a means to counter the common-mode interference in a ECG

system as a result of power lines and other sources, including fluorescent lights. The RLD circuit senses the

common-mode of a selected set of electrodes and creates a negative feedback loop by driving the body with an

inverted common-mode signal. The negative feedback loop restricts the common-mode movement to a narrow

range, depending on the loop gain. Stabilizing the entire loop is specific to the individual user system based on

the various poles in the loop. The ADS1291, ADS1292, and ADS1292R integrates the muxes to select the

channel and an operational amplifier. All the amplifier terminals are available at the pins, allowing the user to

choose the components for the feedback loop. The circuit shown in Figure 40 shows the overall functional

connectivity for the RLD bias circuit.

The reference voltage for the right leg drive can be chosen to be internally generated (AVDD + AVSS) / 2 or it

can be provided externally with a resistive divider. The selection of an internal versus external reference voltage

for the RLD loop is defined by writing the appropriate value to the RLDREF_INT bit in the RESP2 register.

(1)

Typical values.

Figure 40. RLD Channel Selection

If the RLD function is not used, the amplifier can be powered down using the PDB_RLD bit. This bit is also used

in daisy-chain mode to power-down all but one of the RLD amplifiers.

The functionality of the RLDIN pin is explained in the Input Multiplexer section.

ADS1291IPBS Datasheet(PDF) 36 Page - Texas Instruments

ADS1291IPBS Datasheet(HTML) 36 Page - Texas Instruments

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