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AS3648

Datasheet, Confidential - D e ta i l e d D e s c r i p t i o n

Figure 19. Device Shutdown and Wakeup

In shutdown mode once pin SCL goes high for the first time, the internal counter shown in Figure 19 is immediately

the I

Purpose of this circuit

The purpose of this circuit is an additional security mechanism.

Assume the user programmed torch or indicator operation (there is no timeout for these operating modes) and the bat-

tery slowly drops below the undervoltage limit of the system. The processor would get an reset by the PMIC and the

LDO operating VDD_I/F is switched off, but the processor might not have been able to switch-off the torch/indicator

operation of the AS3648. Due to the implemented security mechanism the AS3648 detects a power off of VDD_I/F and

automatically enters shutdown.

Current consumption in standby/shutdown mode

The AS3648 is designed to draw minimum current in standby and shutdown mode. There is a small difference in cur-

rent consumption between these two operating modes (typ. 300nA) only due to the internal level shifters (see the

schmitt trigger input buffers connected to SCL and SDA in Figure 19) for shifting up the voltage on SCL/SDA (VDD_I/F

e.g. 1.8V) to the supply voltage on VIN (e.g. 3.7V). If the AS3648 is driven with digital levels close to 0V/VIN, the cur-

rent consumption for standby mode is identical to shutdown mode.

Operating Mode and Currents

The output currents and operating mode are selected according to the following table:

Table 5. Operating Mode and current settings

AS3648 configuration

operating mode and currents

mode_

setting

(see

page

26)

out_on

(see

page

27)

Condition

Mode

LED_OUT1/2

output current

SCL

low

for

OUT

1

XX

X

X

if previous operating

mode was indicator,

assist light or flash mode

shutdown

all registers are reset to

their default values

0







 

 

  

  

  

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AS3648