ASD1194 Datasheet, PDF (61/76 Pages) Texas Instruments – Low-Power, 8-Channel, 16-Bit Analog Front-End for Biopotential Measurements

ADS1194, ADS1196
ADS1198
www.ti.com
SBAS471C – APRIL 2010 – REVISED NOVEMBER 2011
PACE DETECT
The ADS1194/6/8 provide flexibility for pace detection with external hardware by bringing out the output of the
PGA at two pins: TESTP_PACE_OUT1 and TESTN_PACE_OUT2.
External Hardware Approach
The ADS1194/6/8 provide the option of bringing out the output of the PGA; see Figure 53. External hardware
circuitry can be used to detect the presence of the pulse. The output of the pace detection logic can then be fed
into the device through one of the GPIO pins. The GPIO data are transmitted through the SPI port. Two of the
eight channels can be selected using register bits in the PACE register, one from the odd-numbered channels
and the other from the even-numbered channels. During the differential to single-ended conversion, there is an
attenuation of 0.4. Therefore, the total gain in the pace path is equal to (0.4 × PGA_GAIN). The pace out signals
are multiplexed with the TESTP and TESTN signals through the TESTP_PACE_OUT1 and
TESTN_PACE_OUT2 pins respectively. The channel selection is done by setting bits[4:1] of the PACE register.
If the pace circuitry is not used, the pace amplifiers can be turned off using the PD_PACE bit in the PACE
register.
Note that if the output of a channel connected to the WCT amplifier (for example, the V_LEAD channels) is
connected to one of the pace amplifiers for external pace detection, the artifact of chopping appears at the pace
amplifier output. Refer to the Wilson Center Terminal (WCT) and Chest Leads section for more detials.
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