ADAS1000-4BSTZ datasheet(46/80 Pages) AD

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ADAS1000-3/ADAS1000-4

Data Sheet

Rev. B | Page 46 of 80

FILTERING

Figure 72 shows the ECG digital signal processing. The ADC

sample rate is programmable. In high performance mode, it

is 2.048 MHz; in low power mode, the sampling rate is reduced

to 1.024 MHz. The user can tap off framing data at one of three

data rates, 128 kHz, 16 kHz, or 2 kHz. Note that although the

data-word width is 24 bits for the 2 kHz and 16 kHz data rate,

the usable bits are 19 and 18, respectively.

The amount of decimation depends on the selected data rate,

with more decimation for the lower data rates.

Four selectable low-pass filter corners are available at the 2 kHz

data rate.

Filters are cleared by a reset. Table 16 shows the filter latencies

at the different data rates.

Figure 72. ECG Channel Filter Signal Flow

Table 16. Relationship of ECG Waveform to Pace Indication1, 2, 3

Data Rate

Conditions

Apparent Delay of ECG Data Relative to Pace Event4

2 kHz

450 Hz ECG bandwidth

0.984 ms

250 Hz ECG bandwidth

1.915 ms

150 Hz ECG bandwidth

2.695 ms

40 Hz ECG bandwidth

7.641 ms

16 kHz

109 μs

128 kHz

1 ECG waveform delay is the time required to reach 50% of final value following a step input.

2 Guaranteed by design, not subject to production test.

3 There is an unavoidable residual uncertainty of 8 μs in determining the pace pulse trailing edge.

4 Add 38 μs to obtain the absolute delay for any setting.

2.048MHz

ADC DATA

14-BITS

2.048MHz

128kHz

–3dB AT 13kHz

ACLO

CARRIER

NOTCH

2kHz

AC LEAD-OFF

DETECTION

PACE

DETECTION

128kHz DATA RATE

16-BITS WIDE

AVAILABLE DATA RATE

CHOICE OF 1:

40Hz

150Hz

250Hz

(PROGRAMMABLE BESSEL )

~7Hz

16kHz DATA RATE

24-BITS WIDE

18 USABLE BITS

2kHz DATA RATE

24-BITS WIDE

19 USABLE BITS

128kHz

16kHz

–3dB AT 3.5kHz

2kHz

–3dB AT 450Hz

16kHz

CALIBRATION

31.25Hz DATA RATE

24-BITS WIDE

~22 USABLE BITS

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