AS7058 datasheet(24/199 Pages) AMSOSRAM

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AS7058

Functional description

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DS001077 • v2-00 • 2025-Sep-24

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7.1

LED driver

The PPG block in the AS7058 features two independent LED current drivers connected to

eight LED input pins via two multiplexers. The two LED current sinks have 8-bit resolution with

four programmable full-scale range settings of 25 mA, 150 mA, 225 mA, and 300 mA (typ.).

The lowest range with 25 mA is supposed to be used in combination with the VCSEL emitter

technology. Both drivers include their protection block to supervise the power supply and

interrupt when a malfunction is detected, which would violate laser safety regulations. The

configuration of the LED drivers can be uniquely set for each measurement. The

SUBY_DRVX_SEL defines which LED is selected for each sub sample measurement.

Table 6: LED driver and MUX configuration

SUBy_DRV1_SEL

SUBy_DRV2_SEL

LED1

LED5

LED2

LED6

LED3

LED7

LED4

LED8

Figure 22 shows how the two LED drivers are connected to the eight LED pins and how the

VCSEL protection block is integrated. The minimum LED supply voltage VLED depends on the

forward voltage of the selected LEDs and the minimum driver headroom voltage which is

shown in Table 7. Since AS7058 current sinks support up to four different current operation

ranges the minimum driver headroom voltage is also dependent on the selected LED driver

full-scale range. Therefore, the minimum voltage that needs to be applied is the sum of the

forward voltage of the LED and the LED driver headroom voltage depending on the selected

LED driver full scale range.

Table 7: LED driver full-scale range headroom voltage

LED driver full-scale range (mA)

LED driver headroom voltage (mV)

300

150

400

225

550

300

750

The VLED supply voltage must be above the sum of both voltages to enable proper regulation of

the LED driver and to guarantee the configured LED current for each driver. A lower supply

voltage can result in increased noise behavior and not reaching target LED currents.

AS7058 Datasheet(PDF) 24 Page - ams-OSRAM AG

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