AS7058 datasheet(33/199 Pages) AMSOSRAM

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AS7058

Functional description

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Individual configurations for each PPG ADC are the photodiode assignments via register

PPG1_PDSELx and PPG2_PDSELx as well as the offset DAC currents for ambient light

rejection which can be configured via IOS_PPG1_SUBx and IOS_PGG2_SUBx registers.

7.5.1

PPG measurement modes

AS7058 does support three basic measurement modes which are:

•

Single Measurement Mode

•

Multi Measurement Mode

•

Interleaved Measurement Mode

The three measurement modes covered in this chapter are basic measurement modes which

do not support any kind of ambient light compensation. If ambient light compensation

measurement modes are desired please refer to chapter 7.5.2 Ambient light compensation.

However, it’s worth mentioning that all measurement modes for ambient light compensation to

rely on the basic principle and timing of the Single Measurement mode which is described in

this chapter and illustrated in Figure 30.

7.5.1.1

Single measurement

The Single Measurement mode is the simplest measurement which can be selected and

assigned to a subsample as a measurement. A simplified timing diagram to explain the

operation mode and working principle of the Single Measurement is shown in Figure 30. Once

a Single measurement is executed, the first step in the measurement procedure is that the

assigned photodiode is connected via the internal multiplexers to the selected ADC channel. At

the same time a DAC offset current, which is setup in the IOS_PPG1_SUBx for, is applied to

the summing node of the selected ADC and the photodiode input. After a short delay, which

can be configured as part of the chip configuration, the LEDs with the configured LED currents

are enabled for the measurement and in parallel, the ADC modulator is started. After a

configurable modulator reset time, the SINC down-sampler filter is fed with data. The

measurement time depends now very much on the configuration of the SINC filter, filter order

and internal clock speed of AS7058. Once the measurement time has elapsed the sample data

is written to the FIFO memory and ready for readout by a host MCU.

AS7058 Datasheet(PDF) 33 Page - ams-OSRAM AG