AS1170 datasheet(23/53 Pages) OSRAM

23 / 53 page

AS1170

Detailed description

Datasheet

• PUBLIC • Document Feedback

DS001083

• v2-00 • 2024-Feb-05

23 / 53

7.5.7

Flash current reductions

Current reduction by VIN measurements in flash mode

Due to the high load of the flash driver and the ESR of the battery (especially critical at low

temperatures), the voltage on the battery drops. If the voltage drops below the reset threshold

of the system would reset. To prevent this condition the AS1170 monitors the battery voltage

and keeps it above vin_low_v_run as follows:

Before a flash is started the voltage on VIN is measured. If the voltage is below the setting of

vin_low_v the fault_uvlo is set and the flash is disabled (driver stays in shutdown) if

vin_low_v_shutdown=1.

During flash, if the voltage on VIN drops below the threshold defined by vin_low_v_run, the

flash current is reduced (or ramping of the current is stopped during flash current startup) and

fault_uvlo is set. The timing for the reduction of the current is 8 µs/LSB current change.

During the flash pulse the actual used current can be readout by the register

led_current_actual.

After the flash pulse the minimum current can be readout by the register led_current_min - this

allows to adjust the camera sensitivity (gain or iso-settings) for the subsequent flash pulse (e.g.

when using a pre-flash and a main flash pulse).

AS1170 数据表(PDF) 23 Page - OSRAM GmbH