Datasheet

ADAS1000/ADAS1000-1/ADAS1000-2 Data Sheet
Rev. A | Page 38 of 80
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
precautions 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 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 67 shows the
connections at RESPDAC_xx paths for the extended respiration
configuration. Again, the EXT_RESP_xx paths can be
connected 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 67. Respiration Measurement Using External Capacitor
±1V
±1V
LPF
LA CABLE
ECG1_LA
EXT_RESP_LA
ECG2_LL
EXT_RESP_LL
ECG3_RA
EXT_RESP_RA
ADAS1000
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
09660-024