AS3649

Datasheet - Detailed Descr i p ti on

www.ams.com/AS3649

1.0-2

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8 Detailed Description

The AS3649 is a high performance DCDC step up converter with internal PMOS and NMOS switches. Its output is connected to one or two flash

LEDs

SDA and SCL in I

The actual operating mode like standby, torch light, indicator or flash mode, can then be chosen by the interface. If not in standby mode, the

device automatically enters shutdown and resets all registers by setting pin ON=0.

The AS3649 includes a fixed frequency DCDC step-up with accurate startup control. Together with the current source (on LED_OUT1/2) it

includes several protection and safety functions.

8.1 Internal Circuit Diagram

Figure 16. Internal Circuit Diagram

8.2 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 sources), the ramp up is temporarily stopped in order for the DCDC to return to

regulation

1. If two LEDs are connected, it is possible to operate each of the two LEDs individually as the LED current can be

selected individually.

2. The actual value of the LED current setting can be readout by the register led_current_actual (see page 31) to allow

the camera processor to adopt to the actual operating conditions.





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