ADP1660ACBZ-R7 datasheet(16/28 Pages) AD

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ADP1660

Data Sheet

Rev. 0 | Page 16 of 28

SAFETY FEATURES

For critical fault conditions—such as output overvoltage, flash

timeout, LED output short circuit, and overtemperature condi-

tions—the ADP1660 has built-in protection modes. If a critical

fault occurs, the LED1_EN and LED2_EN bits in Register 0x0F

are set to 0 and the driver shuts down. The appropriate fault bit

is set in the fault information register (Register 0x0C). The pro-

cessor can read the fault information register through the I2C

interface to determine the nature of the fault condition. When

the fault register is read, the fault bit is cleared.

If a noncritical event occurs, the LED driver continues to oper-

ate. Noncritical events include TxMASK event, dc current limit

reached, or soft inductor current limit reached. The corresponding

information bits are set in the fault information register

(Register 0x0C) until the processor reads them.

SHORT-CIRCUIT FAULT

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

lator disconnects the dc path between the battery and the LED,

protecting the system from an LED short circuit. The LED1 and

LED2 pins feature short-circuit protection that monitors the LED

voltage when the LED driver is enabled. If the voltage on the LED1

or LED2 pin remains below the short-circuit detection threshold,

a short circuit is detected, and Bit 6 of the fault information register

(Register 0x0C) is set high. The ADP1660 remains disabled until

the processor clears the fault register.

OVERVOLTAGE FAULT

The ADP1660 contains a comparator at the VOUT pin that

monitors the voltage between VOUT and PGND. If the voltage

exceeds 5.5 V (typical), the ADP1660 shuts down. Bit 7 in the

fault information register (Register 0x0C) is read back as high.

The ADP1660 is disabled until the fault is cleared, ensuring

protection against an open circuit, which would cause an

overvoltage condition.

DYNAMIC OVERVOLTAGE PROTECTION MODE

Dynamic overvoltage protection (OVP) mode is a programmable

feature that prevents the VOUT voltage from exceeding the OVP

level while maintaining as much current as possible through the

LEDs. Dynamic OVP mode prevents an overvoltage fault in the

case of a much higher than expected LED forward voltage. If the

LED forward voltage is reduced due to a rise in LED tempera-

ture, the ADP1660 transitions out of dynamic OVP mode and

regulates the LED at the programmed current level. To enable

dynamic OVP mode, set Bit 6 of Register 0x03 high.

TIMEOUT FAULT

If hardware strobe mode is enabled and strobe is set to level-

sensitive mode (Register 0x01, Bits[5:4] = 11) and if the STROBE

pin remains high for longer than the programmed timeout period,

the timeout fault bit (Register 0x0C, Bit 4) is read back as high.

The ADP1660 remains disabled until the processor clears the

fault register. The timeout value is set using the FL_TIM bits

(Bits[3:0]) in Register 0x02.

OVERTEMPERATURE FAULT

If the junction temperature of the ADP1660 rises above 150°C,

a thermal protection circuit shuts down the device. Bit 5 of the

fault information register (Register 0x0C) is set high. The ADP1660

remains disabled until the processor clears the fault register.

CURRENT LIMIT

An internal switch limits battery current by ensuring that the

peak inductor current does not exceed the limit programmed

using Bits[7:6] in Register 0x01. By default, the soft inductor

peak current limit mode is disabled (Register 0x03, Bit 7 = 1).

When the soft inductor peak current limit is disabled and the

peak inductor current exceeds the limit, Bit 1 of the fault infor-

mation register (Register 0x0C) is set high. The ADP1660 shuts

down and remains disabled until the processor clears the fault

When the soft inductor peak current limit is enabled (Register

0x03, Bit 7 = 0) and the peak inductor current reaches the limit,

Bit 1 of the fault information register (Register 0x0C) is set high.

The inductor and LED current cannot increase further, but the

ADP1660 continues to operate.

INPUT UNDERVOLTAGE

The ADP1660 includes a battery undervoltage lockout circuit.

During fixed 5 V output or LED operation, if the battery voltage

falls below the input UVLO threshold (2.4 V typical), the ADP1660

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

default values when the voltage rises above the UVLO rising

threshold.

SOFT START

The ADP1660 uses a soft start 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 bits in the fault information register (Register 0x0C) are

cleared automatically when the processor reads the fault register

(provided that the faults no longer exist).

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