Datasheet

ADS1293

SNAS602B –FEBRUARY 2013–REVISED MARCH 2013

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Analog Pace Channel

The ADS1293 features an additional analog pace channel to process pulses from a pace maker. The analog

pace channel is suitable for low power applications where the device can be configured for low data rates in ECG

mode only, while an analog channel detects PACE pulses. This channel consists of a traditional three opamp

instrumentation amplifier and is designed to amplify an ECG signal in a typical bandwidth, as specified in the

ELECTRICAL CHARACTERISTICS table, allowing for external circuitry to detect the PACE pulses. The analog

pace implementation inside the ADS1293 is depicted in Figure 19. The analog pace channel is not limited to

PACE detection; it is a full analog channel that could be used to pre-amplify signals, for instance, from a

respiration sensor.

The output voltage of the analog pace channel is:

Vpaceout = 3.5 × (Vinp – Vinm) + RLDREF (12)

Where Vinp and Vinm are the positive and negative inputs of the analog pace channel. The input pins of this

channel can be selected in the FLEX_PACE_CN register and can connect to any of the IN1 through IN6 pins.

Note there is no battery monitoring option available through this channel. There is, however, the reference

voltage test mode available as described in Test Mode.

Figure 19. Analog Pace Channel Instrumentation Amplifier

The output of the analog pace channel can be multiplexed to the WCT or RLDIN pin using the AFE_PACE_CN

the Right Leg Drive amplifier is connected to the RLDREF pin. When PACE2WCT = 1, the output is routed to the

WCT terminal, and the WCT terminal is disconnected from the Wilson output. In this case, the Wilson output can

still be connected internally to the IN6 pin using the WILSON_CN register. The analog pace channel is disabled

when SHDN_PACE = 1 to save power when it is not used.

The analog pace channel is designed to drive a high pass filter and can directly drive a capacitive load of 100pF.

For analog pace detection, it is recommended to have a band pass filter at the output of the analog pace

channel, amplify the resulting signal with a relatively high bandwidth amplifier, and compare the amplified pulses

with a relatively high speed window comparator. The bandwidth of the band pass filter, gain of the amplification,

and the thresholds of the window comparator should be tuned so the comparators trigger on pacemaker pulses,

but not to other signals present in the ECG environment.

Product Folder Links: ADS1293