Datasheet

RLD
Amp
(AVDD+AVSS)/2
RLDREF_INT
RLDREF_INT
RLD_REF
RLD_OUT
RLD_INV
RLD
ADS129x
WCT_TO_RLD
FromWCTAmplifiers
RLD_REF
WCT
RLDINVRLD
OUT
RLD
REF
RLDIN
VA1-8
Device2
VA1-8
RLDINVRLD
OUT
RLD
REF
RLDIN
VA1-8
DeviceN
VA1-8
Power-Down Power-Down
RLDINVRLD
OUT
RLD
REF
RLDIN
VA1-8
Device1
VA1-8
ToInputMUX ToInputMUX ToInputMUX
ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
www.ti.com SBAS459I –JANUARY 2010–REVISED JANUARY 2012
WCT as RLD
In certain applications, the right leg drive is derived as the average of RA, LA, and LL. This level is the same as
the WCT voltage. The WCT amplifier has limited drive strength and thus should be used only to drive very high
impedances directly. The ADS129x provide an option to internally buffer the WCT signal by setting the
WCT_TO_RLD bit in the CONFIG4 register. The RLD_OUT and RLD_INV pins should be shorted external to the
device. Note that before the RLD_OUT signal is connected to the RLD electrode, an external amplifier should be
used to invert the phase of the signal for negative feedback.
Figure 62. Using the WCT as the Right Leg Drive
RLD Configuration with Multiple Devices
Figure 63 shows multiple devices connected to an RLD.
Figure 63. RLD Connection for Multiple Devices
Copyright © 2010–2012, Texas Instruments Incorporated Submit Documentation Feedback 67
Product Folder Link(s): ADS1294 ADS1294R ADS1296 ADS1296R ADS1298 ADS1298R