AS7058 datasheet(48/199 Pages) AMSOSRAM

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AS7058

Functional description

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7.7.1

ECG measurement system

The ECG (electrocardiogram) amplifier is a high impedance, low noise instrumentation

amplifier with a configurable integrated high-pass filter. It also includes circuitry to apply a

stimulus to the inputs to detect lead-off conditions by post-processing the input signals in the

digital domain. In order to further improve noise performance, it is recommended to enable

digital post processing filters to attenuate 50 Hz and 60 Hz noise signals. Please refer to

chapter 7.7.2 for on-chip signal processing options.

Figure 41: ECG amplifier block diagram

The ECG signal amplification is obtained from two stages of amplification which are INA1 and

INA2 like it is shown in Figure 41. The first amplifier stage INA1 does support 4 different gain

settings which can be configured via register ECGAMP_INA1_GAIN. The second preamplifier

INA2 features a gain range from 1 to 128 which can be configured via ECGAMP_INA2_GAIN

ECGAMP_CHOP1_EN and ECGAMP_CHOP2_EN. They also have separate chopper clock

signals whose chopper frequency can be controlled via ECGAMP_CHOP1_CLK and

ECGAMP_CHOP2_CLK register.

The integrated high pass filter does support four different cutoff frequencies with 0.22 Hz,

0.33 Hz, 5 Hz and 10 Hz which can be enabled with register ECGAMP_HP_EN. The cut of

frequency is a function of the filter clock and internal filter capacity and can be configured via

registers ECGAMP_HP_CSEL and ECGAMP_HP_CLK_FREQ. In case a high pass filter

function is not desired in the target application the filter can also be bypassed by enabling

signal, the ECG block incorporates also an anti-aliasing filter block. The cut off frequency can

be configured to 200 Hz, 270 Hz, 400 Hz and 800 Hz via register ECGMOD_IMUX_LPF_FC

to bypass the anti-aliasing filter via the ADC input multiplexer.

ECG_INP

ECG_INN

ECG_REF

RLD

High Pass Filter

0.22Hz; 0.33Hz;

5Hz; 10Hz

0.8V

Preamplifier

INA1

Anti-Aliasing

Filter

200Hz; 270Hz;

400Hz; 800Hz

ECG_LPF

ECG

GSR

BIOZ_I

BIOZ_Q

ECG_IMUX_GAIN

Buffer

TEMP

ECG_LEAD

MOD 3

Current input

delta-sigma

ECGMOD_IMUX_SEL2<2:0>

ECGMOD_IMUX_LPF_FC<1:0>

Preamplifier

INA2

ECGAMP_INA1_GAIN

ECGAMP_INA2_GAIN

ECGAMP_HP_EN

AS7058 Datasheet(PDF) 48 Page - ams-OSRAM AG

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