ADP1649ACBZ-R7 datasheet(17/28 Pages) AD

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Data Sheet

ADP1649

Rev. 0 | Page 17 of 28

SAFETY FEATURES

For critical fault conditions, such as output overvoltage, flash

timeout, LED output short-circuit, and overtemperature

conditions, the ADP1649 has built-in protection modes. If a

critical fault occurs, OUTPUT_EN (Register 0x04) is set to 0,

and the driver shuts down. The appropriate fault bit is set in the

fault information register (Register 0x05). The processor can

read the fault information register through the I2C interface to

determine the nature of the fault condition. When the fault

If a noncritical event such as an indicator LED open-circuit,

short-circuit, TxMASK1, or TxMASK2 event occurs, or if the dc

or soft inductor current limit is reached, the LED driver continues

operating. The corresponding information bits are set in the

fault information register until the processor reads them.

SHORT-CIRCUIT FAULT

When the flash driver is disabled, the high-side current regulator

disconnects the dc path between the battery and the LED, pro-

tecting the system from an LED short circuit. The LED_OUT

pin features short-circuit protection that monitors the LED

voltage when the LED driver is enabled. If the LED_OUT pin

remains below the short-circuit detection threshold, a short

circuit is detected. Bit 6 of the fault information register is set

high. The ADP1649 remains disabled until the processor clears

the fault register.

OVERVOLTAGE FAULT

The ADP1649 contains a comparator at the VOUT pin that

monitors the voltage between VOUT and GND. If the voltage

exceeds 5.5 V (typical), the ADP1649 shuts down. Bit 7 in the

fault information register is read back as high. The ADP1649 is

disabled until the fault is cleared, ensuring protection against an

open circuit.

DYNAMIC OVERVOLTAGE MODE (DOVP)

Dynamic OVP mode is a programmable feature that limits the

VOUT voltage exceeding the OVP level while maintaining as

much current as possible through the LED. This mode prevents

an overvoltage fault in the case of a much higher than expected

LED forward voltage. If the LED forward voltage reduces due to

the LED temperature rising, the ADP1649 moves out of DOVP

mode and regulates the LED at the programmed current level.

Set Bit 7 of Register 0x07 high to enable the DOVP mode.

TIMEOUT FAULT

When the external strobe mode is enabled (Register 0x04, Bit 2)

and the strobe enable bit is set to the level sensitive mode

(Register 0x04, Bit 5), then, if the STROBE pin remains high for

longer than the programmed timeout period, the timeout fault

bit (Register 0x05, Bit 4) is read back as high. The ADP1649

remains disabled until the processor clears the fault register.

OVERTEMPERATURE FAULT

When the junction temperature of the ADP1649 rises above

150°C, a thermal protection circuit shuts down the device. Bit 5 of

the fault information register is set high. The ADP1649 remains

disabled until the processor clears the fault register.

INDICATOR LED FAULT

The GPIO2 pin features open-circuit and short-circuit protec-

tion in the indicator LED mode. If a short circuit or open circuit

occurs, Bit 2 of the fault information register is set high. The

indicator LED regulator ensures that no damage occurs to the

IC during a fault.

CURRENT LIMIT

The internal switch limits battery current by ensuring that the

peak inductor current does not exceed the programmed limit

(Bit 6 and Bit 7 in Register 0x04 set the current limit). The default

mode of the ADP1649 is soft current-limit mode. If the peak

inductor current limit is reached, Bit 1 of the fault information

further although the ADP1649 continues to operate. If the

ADP1649 has soft current limit disabled and the peak inductor

current exceeds the limit, the device shuts down and Bit 1 of the

fault information register is set high. In this case, the ADP1649

remains disabled until the processor clears the fault register.

INPUT UNDERVOLTAGE

The ADP1649 includes a battery undervoltage lockout circuit.

During 5 V or LED operation, the battery voltage dropping

below the 2.4 V (typical) input UVLO threshold shuts down the

ADP1649. A power-on reset circuit resets the registers to their

default conditions when the voltage rises above the UVLO rising

threshold.

SOFT START

The ADP1649 has a soft start mode that controls the rate of

increase of battery current at startup by digitally controlling the

output current ramp. The maximum soft start time is 0.6 ms.

RESET USING THE ENABLE (EN) PIN

A low to high transition on the EN pin resets all registers to

their default values. Bringing EN low reduces the IQ to 0.2 µA

(typical).

CLEARING FAULTS

The information bits and faults in Register 0x05 automatically

clear when the processor reads the fault register.

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