LED7708 datasheet(43/53 Pages) STMICROELECTRONICS

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LED7708

Recommended operating conditions

Doc ID 022698 Rev 1

43/53

8.7

Fault management

The LED7708 includes some protection to prevent damage to itself and to the backlight. In

order to satisfy these requirements, the following protection has been implemented:

The XFLT pin is an open drain output (active low) and is affected by the following faulty

conditions:

Figure 17.

Internal signals connected to the XFLT pin

8.7.1

Overvoltage protection

The LED7708 protects itself and the external components from excessive output voltage by

monitoring the voltage at the VFB pin. The overvoltage threshold is given by the following

equation, where R1 and R2 are the resistors of the output divider:

Table 23.

Detected faulty conditions

Faulty Condition

Involved Section

Boost output overvoltage (OV)

Boost controller

External MOSFET overcurrent (OC)

Open channel

Current generators

Excessive channel voltage (LED short-circuit)

Overtemperature protection

Whole device

Table 24.

XFAULT pin behavior

Detected fault

Involved flag

XFLT status

Overvoltage protection

OVPF

Low

Overtemperature alert

OTAF

Low

Open channel

CHSTA16:CHSTA01

Low

LED short-circuit

CHSTA16:CHSTA01

Low

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