AS7058 datasheet(68/199 Pages) AMSOSRAM

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AS7058

Functional description

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7.12

Standby mode

AS7058 supports standby operation mode to reduce overall power consumption during the

pause times while no PPG or ECG measurement is ongoing. Especially at very low sample

rates standby mode helps to reduce system power consumption to extend the battery lifetime

of a device. The standby mode function is controlled with up to 14 different standby mode

enable control signals. Each of the fourteen standby enable signals controls a dedicated

hardware block of AS7058. An overview of the 14 different control signals is shown in Table 15

below. Furthermore, it contains information about the related blocks which are necessary for a

certain application. If the device operates in PPG operation mode, only standby enable signals

whose functionality is required for PPG operation need to be enabled via register

STANDBY_ON1 and STANDBY_ON2. In addition to the enable registers each Standby

Enable signal is also connected to a dedicated timing register to define the standby startup

timing of the functional block. A simplified timing diagram of all Standby Enable signals is

shown in Figure 62.

Table 15: Standby mode control signal overview

Standby control

signal

Function

Timing control

registers

Functionality

Standby Enable 1

Controls and enables the internal PLL

and high frequency oscillator.

time_en1

Required for PPG and ECG

operation

Standby Enable 2

Controls and enables the voltage

reference for the LED drivers

time_en2

Required for PPG operation only

Standby Enable 3

Controls and enables on chip

bandgap and bias reference current

time_en3

Required for PPG and ECG

operation

Standby Enable 4

Controls and enables the bypass

functions of the low pass filter

time_en4

Required for PPG and ECG

operation

Standby Enable 5

Controls and enables the bias voltage

block of the current DAC

time_en5

Required for PPG operation only

Standby Enable 6

Controls and enables the PPG

common mode voltage buffer

time1_en6

time2_en6

Required for PPG operation only

Standby Enable 7

Controls and enables the PPG

modulators

time1_en7

time2_en7

Required for PPG operation only

Standby Enable 8

Controls and enables the ECG

common mode voltage buffer

time1_en8

time2_en8