Datasheet

MUX[2:0]=101
TempP
MUX[2:0]= 100
MvddP
(1)
MUX[2:0]= 011
FromLoffP
MUX[2:0]= 000
MUX[2:0]= 110
MUX[2:0]= 001
ToPgaP
ToPgaN
MUX[2:0]= 001
RLDIN
MUX[2:0]= 010
RLD_MEAS
AND
MUX[2:0]= 111
VINP
VINN
MUX[2:0]= 000
FromLoffN
RLD_REF
MUX[2:0]= 010
RLD_MEAS
AND
MvddN
(1)
TempN
MUX[2:0]= 100
MUX[2:0]= 101
ADS129x
MUX
TestP
TestN
TESTP_PACE_OUT1
INT_TEST
INT_TEST
TESTN_PACE_OUT2
INT_TEST
INT_TEST
MUX[2:0]= 011
EMI
Filter
(AVDD+AVSS)
2
ADS1294, ADS1294R
ADS1296, ADS1296R
ADS1298, ADS1298R
SBAS459I –JANUARY 2010–REVISED JANUARY 2012 www.ti.com
THEORY OF OPERATION
This section discusses the details of the ADS129x internal functional elements. The analog blocks are reviewed
first, followed by the digital interface. Blocks implementing ECG-specific functions are covered in the end.
Throughout this document, f
CLK
denotes the frequency of the signal at the CLK pin, t
CLK
denotes the period of the
signal at the CLK pin, f
DR
denotes the output data rate, t
DR
denotes the time period of the output data, and f
MOD
denotes the frequency at which the modulator samples the input.
EMI FILTER
An RC filter at the input acts as an EMI filter on all of the channels. The –3dB filter bandwidth is approximately
3MHz.
INPUT MULTIPLEXER
The ADS129x input multiplexers are very flexible and provide many configurable signal switching options.
Figure 24 shows the multiplexer on a single channel of the device. Note that the device has eight such blocks,
one for each channel. TEST_PACE_OUT1, TEST_PACE_OUT2, and RLD_IN are common to all eight blocks.
VINP and VINN are separate for each of the eight blocks. This flexibility allows for significant device and
sub-system diagnostics, calibration, and configuration. Selection of switch settings for each channel is made by
writing the appropriate values to the CHnSET[2:0] register (see the CHnSET: Individual Channel Settings section
for details) and by writing the RLD_MEAS bit in the CONFIG3 register (see the CONFIG3: Configuration Register
3 subsection of the Register Map section for details). More details of the ECG-specific features of the multiplexer
are presented in the Input Multiplexer subsection of the ECG-Specifc Functions section.
(1) MVDD monitor voltage supply depends on channel number; see the Supply Measurements (MVDDP, MVDDN)
section.
Figure 24. Input Multiplexer Block for One Channel
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Product Folder Link(s): ADS1294 ADS1294R ADS1296 ADS1296R ADS1298 ADS1298R