ADP1653

Data Sheet

Rev. C | Page 16 of 24

HPLED register between 12 (01100 binary) and 31 (11111 binary).

The flash does not turn on until a strobe command is given by

either pulling the STR pin high or by writing a software strobe

The strobe command operates in one of two watchdog timer

modes, timed flash and user-controlled flash, which are

controlled via the state of the timeout configuration

(TMR_CFG) bit of the CONFIG register. If TMR_CFG is set

(1), the flash operates in timed mode. In timed flash, a rising

edge on STR turns on the flash. The flash remains on until the

internal timeout occurs, which is set by the TMR_SET bits of the

CONFIG register, according to the following equation:

(5)

where Code ranges from 0 (0000 binary) to 15 (1111 binary),

allowing for flash periods ranging from 54 ms to 820 ms.

If TMR_CFG is not set (0), the flash operates in user-controlled

timer mode. In user-controlled timer mode, the flash remains

on as long as STR is held high. If STR remains high longer than

and a fault is set in the watchdog timeout (FLT_TMR) bit of the

FAULT register.

The ADP1653 also offers a software strobe option, allowing the

pulling the STR pin high. Setting the SW_STROBE register bit

to 1 initiates a flash cycle. The strobe can operate in either timed

or user-controlled mode, as previously described.

SAFETY FEATURES

Interrupts

For critical system conditions, such as output overvoltage,

watchdog timeout, and overtemperature conditions, the ADP1653

indicates that an interrupt event has occurred by asserting the

active low interrupt output INT. INT is an open-drain output

and should be pulled up to the I/O voltage rail by using a resistor.

of the fault condition after sensing that INT has gone low. Users

can clear a fault by writing 0x00 to the OUT_SEL register. This

brings INT high and clears the FAULT register.

In 2-bit logic interface mode, INT goes low for the same fault

a fault, set CTRL1 and CTRL0 low.

Overvoltage Fault

The ADP1653 contains a comparator at the OUT pin that monitors

the voltage from the high power LED(s) to PGND. If the voltage

(FLT_OV) is read back as high. The ADP1653 is disabled, and

INT remains low until the fault is cleared.

Timeout Fault

If the 2-bit logic interface is used, the maximum duration for

flash being enabled (CTRL1/CTRL0 =1) is preset to 820 ms.

If CTRL1 and CTRL0 remain high for longer than 820 ms, INT

goes low and the ADP1653 is disabled.

FLT_TMR bit in the FAULT register is read back as high. The

ADP1653 is disabled, and INT remains low until the fault is

cleared.

Overtemperature Fault

If the junction temperature of the ADP1653 rises above 155°C,

a thermal protection circuit shuts down the LED driver and

register is read back as high. The ADP1653 is disabled, and INT

remains low until the fault is cleared.

Short-Circuit Fault

The HPLED pin features short-circuit protection that disables

the ADP1653 if it detects a short circuit to ground at the cathode

of the LED(s). The ADP1653 monitors the HPLED voltage once

the part is enabled in torch mode. If after 820 ms the HPLED

pin remains grounded, a short circuit is detected. INT goes low,

and Bit D3 (FLT_SCP) of the FAULT register is read back as high.

Avoid false triggering of the Short Circuit Fault by not changing

the torch current level while the short-circuit detection circuit is

making a measurement of HPLED pin voltage. Do not change

torch setting directly between two non-zero torch levels 750 ms

to 900 ms after the torch has been enabled. To change torch

mode current level between two non-zero torch levels 750 ms to

900 ms after enabling torch mode, use the following sequence:

Torch Current Setting #1

Torch Current Setting = 0

Torch Current Setting #2

Torch mode and flash modes can be enabled or disabled at

any time.

Input Undervoltage

The ADP1653 includes an input undervoltage lockout circuit.

If the battery voltage drops below the 2.7 V (typical) input UVLO

threshold, the ADP1653 shuts down and the input current drops to

less than 45 µA to prevent deep discharge of the battery. In this

case, the system register information is lost, and when power is

reapplied, a power-on reset circuit resets the registers to their

default conditions.

Current Limit

The internal LX switch limits battery current by ensuring that

the peak inductor current does not exceed 2.1 A (typical). If the

SETI, SETT, or SETF pins accidentally connect to ground, the

reference current is limited to a maximum of 1 mA.