AS7058 datasheet(30/199 Pages) AMSOSRAM

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AS7058

Functional description

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7.4

PPG/ECG sequencer

In order to unload MCU with re-occurring measurement tasks to be triggered and its related

timing constraints, AS7058 has a built in measurement sequencer which controls all relevant

PPG and ECG/Bioimpedance blocks with its corresponding timings. An overview of the

sequencer timing diagram is shown in Figure 27.

Figure 27: PPG/ECG sequencer timing diagram

The sequencer basically supports three different sample rates which can be configured

independently from each other. All timings for the sequencer are derived from the on-chip

32 kHz oscillator. The PPG measurement channel can be configured independently from the

ECG/BioZ sampling periods. Whereas the PPG channel allows for one sample rate for each

PPG sample measurement the ECG/BioZ sequencer supports two different sample rates

which are called SEQ1 Sample Period and SEQ2 Sample Period. The benefit of having two

different sample rates as part of the ECG/BioZ sequencer, like it is shown in Figure 27, is that

an ECG measurement can for example run with SEQ2 at a sample rate of e.g. 400 Hz and the

AC lead off detection can run with SEQ1 at a much higher frequency.

Figure 28: Sequencer clock generation

PPG

Seqeuncer

ECG / BioZ

Sequenzer

PPG

Sample

PPG

Sample

PPG

Sample

PPG

Sample

PPG Sample Period

ECG/BioZ

Sample

SEQ2

SEQ1

SEQ1 Sample Period

ECG/BioZ

Sample

SEQ1

ECG/BioZ

Sample

SEQ2

SEQ1

ECG/BioZ

Sample

SEQ1

SEQ1 Sample Period

ECG/BioZ

Sample

SEQ1

SEQ1 Sample Period

ECG/BioZ

Sample

SEQ1

SEQ 2 Sample Period

32kHz

On Chip Oscillator

ECG Base Divider

16 bit

PPG Clock Divider

16 bit

ECG 2 Clock Divider

16 bit

ECG2_FREQDIVH[7: 0]

ECG2_FREQDIVL[7:0]

PPG_FREQH[7:0]

PPG_FREQL[7: 0]

Clock to PPG Sequencer

Clock to ECGPPG Sequencer 2

ECG_FREQH[7:0]

ECG_FREQL[7:0]

ECG 1 Clock Divider

16 bit

ECG1_FREQDIVH[7: 0]

ECG1_FREQDIVL[7:0]

Clock to ECG/PPG Sequencer 1

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