LM3565

SNVS957 – JANUARY 2013

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Fault Protections

The LM3565 has a number of fault protection mechanisms designed to not only protect the LM3565 itself, but

also to reset the system. Active fault protections include:

•

Over-Voltage Protection (VOUT)

•

Short-Circuit Protection (VOUT and VLED)

•

Over-Temperature Protection

•

Flash Time-Out

•

Under-Voltage Lock-Out (UVLO)

•

Output Capacitor Open Protection

In the event that any of these faults occur, the LM3565 will set a flag in the appropriate Fault Register (Address

0x08 or 0x09) and place the part into standby. Normal operation cannot resume until the fault has been fixed and

an I2C read of the fault register (0x08 and/or 0x09) has been completed. All faults are cleared upon reading the

Fault Registers (0x08 and 0x09).

Output Over-Voltage Protection (OVP)

An OVP fault is triggered when the output voltage of the LM3565 reaches a value greater than 9.5V (typ). The

OVP condition is cleared when the output voltage (VOUT) is able to operate below 9.5V. An output capacitor or an

LED that have become an open circuit can cause an OVP event to occur. This fault is reported to the OVP fault

bit in the Fault Register (bit7 in address 0x05).

Output and LED Short Circuit Protection (SC)

An SC fault is triggered when the output voltage (VOUT) and/or the LED voltage (VLED) does not reach 0.8V in

0.5 ms. The short circuit condition is cleared when the output (VOUT) is allowed to reach its steady state target

and when the LED voltage rises above 0.8V. A shorted output capacitor or a shorted LED could cause this fault

to occur. This fault is reported to the SC fault bit in the Fault Register (bit6 in address 0x08).

Over-Temperature Protection (OTP)

An OTP fault is triggered when the diode junction temperature of the LM3565 reaches an internal temperature of

around 150°C. The OTP condition is cleared when the junction temperature falls below 115°C and the fault

register is read. A printed circuit board (PCB) with poor thermal dissipation properties and very high ambient

temperatures (greater that 85°C) could cause this fault to occur. Refer to Texas Instruments Application Note:

AN-1112: DSBGA Wafer Level Chip Scale Package for more information regarding proper PCB layout. This fault

is reported to the OTP fault bit in the Fault Register (bit5 in address 0x08).

Flash Time-Out (TO)

The TO fault will be triggered whenever a flash is initiated with a level-sensitive Strobe event controlled by a

camera module and the Strobe pulse duration exceeds the selected Flash Time-out duration. This fault is

reported to the TO fault bit in the Fault Register (bit4 in address 0x08). This bit only gets set when PWM Mode is

disabled.

Under-Voltage Lock-Out (UVLO)

An Under-Voltage Lock-Out (UVLO) fault occurs when the input voltage at the LM3565 drops below 2.4V (typ).

When this fault occurs, the LM3565 will be forced into Standby Mode and the UVLO bit will be set to a '1'. To exit

a UVLO state, the input voltage to the LM3565 must increase by 100 mV (typ.) and the UVLO Fault bit must be

cleared. This fault is reported to the UVLO fault bit in the Fault Register (bit0 in address 0x08).

Output Capacitor Open Protection (CO)

An Output Capacitor Open fault is triggered when the LM3565 detects that the capacitance at the VOUT pin has

dropped below the acceptable value (typically 0.1 µF). This fault indicates that the output capacitors are either

disconnected or damaged and is reported to the Output Capacitor fault bit in the ADC Control Register (bit4 in

address 0x09). Once an Output Capacitor Open fault is detected, the State Machine Reset bit (LVRS) in the Low

Voltage Control register (0x04) has to bo toggled between a '1' and a '0' in order for normal operation to resume.

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