Datasheet

Data Sheet ADAS1000-3/ADAS1000-4
Rev. A | Page 35 of 76
External Respiration Path
The EXT_RESP_xx pins are provided for use either with the
ECG electrode cables or, alternatively, with a dedicated external
sensor independent of the ECG electrode path. Additionally,
the EXT_RESP_xx pins are provided such that the user can
measure the respiration signal at the patient side of the RFI/
ESIS protection filters. In this case, the user must take pre-
cautions to protect the EXT_RESP_xx pins from any signals
applied that are in excess of the operating voltage range.
External Respiration Capacitors
If necessary, the ADAS1000-4 allows the user to connect
external capacitors into the respiration circuit to achieve higher
resolution (<200 mΩ). This level of resolution requires that the
cable impedance be ≤1 kΩ. The diagram in Figure 64 shows the
connections at RESPDAC_xx paths for the extended respiration
configuration. Again, the EXT_RESP_xx paths can be con-
nected at the patient side of any filtering circuit; however, the
user must provide protection for these pins. While this external
capacitor mode requires external components, it can deliver a
larger signal-to-noise ratio. Note again that respiration can be
measured on only one lead (at one time); therefore, only one
pair of external respiration paths (and external capacitors) may
be required.
Figure 64. Respiration Measurement Using External Capacitor
LA CABLE
ECG1_LA
EXT_RESP_LA
ECG2_LL
EXT_RESP_LL
ECG3_RA
EXT_RESP_RA
ADAS1000-4
46.5kHz TO
64kHz
46.5kHz TO
64kHz
OVERSAMPLED
5kΩ
1kΩ
1kΩ
1kΩ
5kΩ
100pF
100pF
RESPDAC_LA
RESPDAC_RA
RESPDAC_LL
1nF TO 10nF
1nF TO 10nF
MUTUALLY
EXCLUSIVE
MUTUALLY
EXCLUSIVE
RESPIRATION DAC
DRIVE +
CABLE AND ELECTRODE
IMPEDANCE < 1kΩ
LL CABLE
RA CABLE
FILTER
FILTER
FILTER
RESPIRATION
MEASURE
RESPIRATION DAC
DRIVE –
HPF
IN-AMP AND
ANTI-ALIASING
MAGNITUDE
AND
PHASE
SAR
ADC
10997-024
±1V
±1V
LPF