ADAS1000-4BSTZ datasheet(38/80 Pages) AD

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ADAS1000-3/ADAS1000-4

Data Sheet

Rev. B | Page 38 of 80

envelope and perform the peak detection needed to establish

breathing (or lack thereof).

Respiration measurement is available on one of the leads

(Lead I, Lead II, or Lead III) or on an external path via a

pair of dedicated pins (EXT_RESP_LA, EXT_RESP_RA, or

EXT_RESP_LL). Only one lead measurement can be made

at one time. The respiration measurement path is not suited

for use as additional ECG measurements because the internal

configuration and demodulation do not align with an ECG

measurement. The respiration signal processing path is not

reconfigurable for ECG measurements, as it is specifically

designed for the respiration signal measurement.

Internal Respiration Capacitors

The internal respiration function uses an internal RC network

(5 kΩ/100 pF), and this circuit is capable of 200 mΩ resolution

(with up to 5 kΩ total path and cable impedance). The current

is ac-coupled onto the same pins that the measurement is

sensed back on. Figure 67 shows the measurement on Lead I,

but, similarly, the measurement can be configured to measure

on either Lead II or Lead III. The internal capacitor mode requires

no external capacitors and produces currents of ~64 μA p-p

amplitude when configured for maximum amplitude setting

(±1 V) through the RESPCTRL register (see Table 30).

Table 12. Maximum Allowable Cable and Thoracic Loading

Cable Resistance

Cable Capacitance

R < 1 kΩ

C < 1200 pF

1 kΩ < R < 2.5 kΩ

C < 400 pF

2.5 kΩ < R < 5 kΩ

C < 200 pF

RTHORACIC < 2 kΩ

Figure 67. Simplified Respiration Block Diagram

LA CABLE

ECG1_LA

EXT_RESP_LA

ECG2_LL

EXT_RESP_LL

ECG3_RA

EXT_RESP_RA

ADAS1000-4

OVERSAMPLED

5kΩ

100pF

±1V

RESPIRATION DAC

DRIVE +

CABLE AND ELECTRODE

IMPEDANCE < 5kΩ

LL CABLE

RA CABLE

FILTER

LPF

RESPIRATION

MEASURE

RESPIRATION DAC

DRIVE–

HPF

IN-AMP AND

ANTI-ALIASING

MAGNITUDE

AND

PHASE

SAR

ADC

46.5kHz TO

64kHz

46.5kHz TO

64kHz

ADAS1000-4BSTZ Datasheet(PDF) 38 Page - Analog Devices

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