Datasheet

51kW

100kW

47nF

Skin,

ElectrodeContact

Model

Patient

Protection

Resistor

AVSS

RLD_SENS

VLEAD_OFF_EN

AND

AVSS

RLD_STAT

Patient

RLD_SENS

VLEAD_OFF_EN

AND

ToADCinput(throughV

connectiontoanyofthechannels).

REF

ILGND_OFF[1:0]

ADS1294, ADS1294R

ADS1296, ADS1296R

ADS1298, ADS1298R

SBAS459I –JANUARY 2010–REVISED JANUARY 2012

www.ti.com

RLD LEAD-OFF

The ADS129x provide two modes for determining whether the RLD is correctly connected:

• RLD lead-off detection during normal operation

• RLD lead-off detection during power-up

The following sections provide details of the two modes of operation.

RLD Lead-Off Detection During Normal Operation

During normal operation, the ADS129x RLD lead-off at power-up function cannot be used because it is

necessary to power off the RLD amplifier.

RLD Lead-Off Detection At Power-Up

This feature is included in the ADS129x for use in determining whether the right leg electrode is suitably

connected. At power-up, the ADS129x provide two measurement procedures to determine the RLD electrode

connection status using either a current or a voltage pull-down resistor, as shown in Figure 60. The reference

level of the comparator is set to determine the acceptable RLD impedance threshold.

Figure 60. RLD Lead-Off Detection at Power-Up

When the RLD amplifier is powered on, the current source has no function. Only the comparator can be used to

sense the voltage at the output of the RLD amplifier. The comparator thresholds are set by the same LOFF[7:5]

bits used to set the thresholds for other negative inputs.

Product Folder Link(s): ADS1294 ADS1294R ADS1296 ADS1296R ADS1298 ADS1298R