AS1181 datasheet(32/92 Pages) AMSOSRAM

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AS1181

Functional description

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DS001139 • v3-00 • 2026-Apr-01

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7.2.3

Digital safety monitors

7.2.3.1

Illumination time monitor

The illumination time monitor is continuously sampling the PWM ON time applied via both

inputs and comparing the result with the value programmed in “TD_ILLUM_MAX register

(Address 0x1A36)”. In PWM mode the ON time (HIGH Time) is constrained to be maximum

15ms. Therefore, the value in the TD_ILLUM_MAX register shall be less the 15ms in this

mode. (Refer to Table 5: External PWM mode constraints).

If the actual PWM ON time is longer than the value programmed the current sinks get turned

off and the respective interrupt flag is set.

Figure 31 shows the actual implementation – in the 3rd frame (STROBE = yellow) the PWM ON

time changes from 4ms to 10ms – TD_ILLUM_MAX is programmed to 4.1ms.

The current sink (blue) is turned off immediately and the interrupt IRQ_N (green) is pulled to

GND. The interrupt “Illumination Duration” has been set and is informing the Host.

Figure 31: Illumination time monitor example

AS1181 数据表(PDF) 32 Page - ams-OSRAM AG