AS1170 datasheet(17/53 Pages) AMSOSRAM

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AS1170

Detailed description

Datasheet

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DS001083

• v2-00 • 2024-Feb-05

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7.1

Softstart / soft ramp down

During startup and ramp down the LED current is smoothly ramped up and ramped down. If

the DCDC converter goes out of regulation (measured by monitoring the voltage across the

current sinks), the ramp up is temporarily stopped in order for the DCDC to return to

regulation3.

7.2

4 MHz / 1 MHz operating mode switching

If freq_switch_on=1 and in flash and assist light mode (indicator mode or low current mode

using PWM mode -see mode_setting - always will use pulseskip) if led_current1>=40h and

led_current2>=40h and current_boost=0, the DCDC converter always operates in PWM mode

(exception: PFM mode is allowed during startup) to reduce EMI in EMI sensitive systems. For

flash and assist light mode and high duty cycles close to 100% on-time (maximum duty cycle)

of the PMOS, the DCDC converter can switch into a 1 MHz operating mode and maximum

duty cycle to improve efficiency for this load condition4. The DCDC converter returns back to

its normal 4 MHz operating frequency when load or supply conditions change. Due to this

switching between two fixed frequencies the noise spectrum of the system is exactly defined

and predictable. If improved efficiency is required, the fixed switching between 1 MHz / 4 MHz

can be disabled by freq_switch_on=0. In this case pulseskip will be used.

3 The actual value of the LED current setting can be readout by the register led_current_actual to allow the camera processor to

adopt to the actual operating conditions.

4 Efficiency compared to a 4 MHz only DCDC converter forced to operate with minimum duty cycle.

AS1170 데이터시트(PDF) 17 Page - ams-OSRAM AG