ADAS1000BSTZ datasheet(42/80 Pages) AD

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ADAS1000/ADAS1000-1/ADAS1000-2

Data Sheet

Rev. A | Page 42 of 80

Pace Amplitude Threshold

This register (Address 0x07, see Table 32) can be used to set the

minimum valid pace pulse amplitude:

PACEAMPTH setting =

GAIN

VREF

, (corresponds to a

range of 20 µV to 5 mV in the ×1.4 gain setting (GAIN 0))

where:

N = 0 to 255 (8 bits), register default N = 0x24, (PACEAMPTH

= 706 μV in the ×1.4 gain setting)

GAIN = 1.4, 2.1, 2.8, or 4.2 (programmable).

VREF = 1.8 V.

This level would typically be set to be the minimum expected

pace amplitude.

For best results under most operating conditions for both

biventricular and unipolar pacing, it is suggested to set the

pace amplitude threshold to a value of approximately 700 μV

to 1 mV. It is not recommended to set the threshold below

250 μV to avoid ambient noise from the patient. The amplitude

may need to be adjusted much higher than 1 mV when other

medical devices are connected to the patient.

Pace Edge Threshold

This programmable level (Address 0x0E, see Table 39) is used to

find a leading edge, signifying the start of a pace pulse:

PACEEDGETH setting =

GAIN

VREF

(corresponds to a

range of 20 µV to 5 mV in the ×1.4 gain setting)

where:

If N = 0, PACEEDGETH = PACEAMPTH/2, then N = 0 to 255

(8 bits).

GAIN = 1.4, 2.1, 2.8 or 4.2 (programmable).

VREF = 1.8 V.

Pace Level Threshold

This programmable level (Address 0x0F, see Table 40) is used to

find the leading edge peak:

PACELVLTH setting =

GAIN

VREF

, signed (FF = −1,

01 = +1), default = 0

where:

N = 0 to 255 (8 bits).

GAIN = 1.4, 2.1, 2.8 or 4.2 (programmable).

VREF = 1.8 V.

Pace Validation Filter 1

This filter is used to reject sub threshold pulses such as minute

ventilation (MV) pulses and inductive coupled implantable

telemetry systems. It is typically enabled and is controlled via

the PACECTL register, Bit 9 (see Table 29) register. Filter 1

applies to all leads enabled for pace detection.

Pace Validation Filter 2

This filter is also used to reject sub threshold pulses such as

MV pulses and inductive implantable telemetry systems. It is

normally enabled and is controlled via the PACECTL register,

Bit 10 (see Table 29). Filter 2 applies to all leads enabled for pace

detection.

Pace Width Filter

When enabled, this filter searches for an edge of opposite polarity

to the leading edge with a magnitude of at least half the original

trigger. The second edge must be between 100 µs to 2 ms from the

original edge. When a valid pace width is detected, the width is

stored. When disabled only the minimum pulse width of 100 μs

is disabled. This filter is controlled by the PACECTL register, Bit 11

(see

Table 29).

BIVENTRICULAR PACERS

As described previously, the pace algorithm expects the pace

pulse to be less than 2 ms wide. In a pacer where both ventricles

are paced, they can be paced simultaneously. Where they fall

within the width and height limits programmed into the

algorithm, a valid pace will be flagged, but only one pace pulse

may be visible.

With the pace width filter enabled, the pace algorithm seeks

pace pulse widths within a 100 μs to 2 ms window. Assuming

that this filter is enabled and in a scenario where two ventricle

pacer pulses fire at slightly different times, resulting in the pulse

showing in the lead as one large, wider pulse, a valid pace is

flagged so long as the total width does not exceed 2 ms.

PACE DETECTION MEASUREMENTS

Design verification of the ADAS1000 digital pace algorithm

includes detection of a range of simulated pace signals in

addition to using the ADAS1000 and evaluation board with

one pacemaker device connected to various simulated loads

(approximately 200 Ω to over 2 kΩ) and covering the following

4 waveform corners.

•

Minimum pulse width (100 μs), minimum height (to

<300 μV)

•

Minimum pulse width (100 μs), maximum height (up to

1.0 V)

•

Maximum pulse width (2 ms), minimum height (to

<300 μV)

•

Maximum pulse width (2 ms), maximum height (up to

1.0 V)

These scenarios passed with acceptable results. The use of the

ac lead-off function had no obvious impact on the recorded

pace height, width, or the ability of the pace detection algorithm

to identify a pace pulse. The pace algorithm was also evaluated

with the respiration carrier enabled; again, no differences in the

threshold or pacer detect were noted from the carrier.

ADAS1000BSTZ Datasheet(PDF) 42 Page - Analog Devices

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