ADAS1000-4BSTZ datasheet(43/80 Pages) AD

43 / 80 page

Data Sheet

ADAS1000-3/ADAS1000-4

Detection Algorithm Overview

The pace pulse amplitude and width varies over a wide range,

while its shape is affected by both the internal filtering arising

from the decimation process and the low pass nature of the

electrodes, cabling, and components used for defibrillation and

ESIS protection. The ADAS1000-4 provides user programmable

variables to optimize the performance of the algorithm within

the ECG system, given all these limiting elements. The default

parameter values are probably not optimal for any particular

system design; experimentation and evaluation are needed to

ensure robust performance.

Figure 70. Typical Pace Signal

The first step in pace detection is to search the data stream for a

valid leading edge. Once a candidate edge is detected, the algorithm

verifies that the signal looks like a pulse and then begins searching

for a second, opposite polarity edge that meets the pulse width

and amplitude criteria and passes the optional noise filters. Only

the pulses meeting all requirements are flagged as valid pace pulses.

Detection of a valid pace pulse sets the flag or flags in the frame

header register and stores amplitude and width information in

the PACEDATA register (Address 0x1A; see Table 34).

The pace algorithm detects pulses of both negative and positive

polarity using a single set of parameters by tracking the slope of

the leading edge and making the necessary adjustments to internal

parameter signs. This frees the user to concentrate on determining

appropriate threshold values based on pulse shape without

concern for pulse polarity.

Figure 71. Overview of Pace Algorithm

The three user controlled parameters for the pace detection

algorithm are Pace Amplitude Threshold (PACEAMPTH), Pace

Level Threshold (PACELVLTH), and Pace Edge Threshold

(PACEEDGETH).

PACEAMPTH

PACE WIDTH

LEADING EDGE

LEADING EDGE STOP

PACELVLTH

PACEEDGETH

RECHARGE

PULSE

PACE

PULSE

ENABLE PACE DETECTION

SELECT LEADS

FLAG PACE DETECTED

TRAILING

EDGE

DETECTED?

START

START PULSE

WIDTH TIMER

START NOISE

FILTERS (if enabled)

NOISE FILTER

PASSED?

PULSE WIDTH

> 100µs AND <2ms

UPDATE REGISTERS WITH

WIDTH AND HEIGHT

YES

START PACE DETECTION

ALGORITHM

FIND

LEADING EDGE

A > PACEEDGETH?

YES

FIND

END OF

LEADING EDGE

B < PACELVL

YES

PACE AMPLITUDE

> PACEAMPTH

YES

Rev. B | Page 43 of 80

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