ADAS1000 datasheet(41/80 Pages) AD

41 / 80 page

Data Sheet

ADAS1000/ADAS1000-1/ADAS1000-2

Rev. B | Page 41 of 80

Respiration Carrier Frequency

The frequency of the respiration carrier is programmable and

can be varied through the RESPCTL register (Address 0x03, see

Table 30). The status of the HP bit in the ECGCTL register also

has an influence on the carrier frequency as shown in Table 13.

Table 13. Control of Respiration Carrier Frequencies.

RESPALTFREQ1

RESPEXTSYNC1

HP2

RESP-

FREQ1

Respiration

Carrier

Frequency

56.9

51.2

46.5

25.5

1 Control bits from RESPCTL (Register 0x03).

2 Control bit from ECGCTL (Register 0x01).

In applications where an external signal generator is used to

develop a respiration carrier signal, that external signal source

can be synchronized to the internal carrier using the signal

available on GPIO3 when Bit 7, RESPEXTSEL, is enabled in

the respiration control register (see Table 30).

Table 14. Control of Respiration Carrier Frequency

Available on GPIO3

RESPALT-

FREQ1

RESPEXT-

SYNC1

HP2

RESP-

FREQ1

Respiration Carrier

Frequency on GPIO3

XX3

51.2

46.5

25.5

1 Control bits from RESPCTL (Register 0x03).

2 Control bit from ECGCTL (Register 0x01).

3 X = don’t care.

EVALUATING RESPIRATION PERFORMANCE

ECG simulators offer a convenient means of studying the

performance of the ADAS1000. While many simulators offer a

variable-resistance respiration capability, care must be taken

when using this feature.

Some simulators use electrically programmable resistors, often

referred to as digiPOTs, to create the time-varying resistance to

be measured by the respiration function. The capacitances at the

terminals of the digiPOT are often unequal and code-dependent,

and these unbalanced capacitances can give rise to unexpectedly

large or small results on different leads for the same programmed

resistance variation. Best results are obtained with a purpose-

built fixture that carefully balances the capacitance presented to

each ECG electrode.

EXTEND SWITCH ON RESPIRATION PATHS

There is additional multiplexing on the external respiration inputs

to allow them to serve as additional electrode inputs to the existing

five ECG ADC channels. This approach allows a user to configure

eight electrode inputs; however, it is not intended as a true

8-channel/12-lead solution. Time overheads are required to

reconfigure the multiplexer arrangement using the serial interface

in addition to filter the latency as described in Table 16.

The user has full control over the SW1/SW2/SW3 configuration

as outlined in Table 50.

Figure 72. Alternative Use of the Respiration Paths

TO ECG1_LA CHANNEL

TO ECG2_LL CHANNEL

TO ECG3_RA CHANNEL

TO ECG4_V1 CHANNEL

TO ECG5_V2 CHANNEL

EXT_RESP_RA

EXT_RESP_LL

EXT_RESP_LA

SW1a

SW1b

SW1c

SW1d

SW1e

SW2a

SW2b

SW2c

SW2d

SW2e

SW3a

SW3b

SW3c

SW3d

SW3e

TO RESPIRATION CIRCUITRY

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