LP8543

SNVS604D – AUGUST 2009 – REVISED MARCH 2013

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Table 10. Digital LED Fault Detection Thresholds

DIG_COMP[1:0]

Threshold Voltage (V)

00

3

01

5

10

7

11

9

When Fault is detected the FAULT pin will be pulled down (open drain output), and corresponding status register

bit is set. To clear the fault user must read the status register.

Note: LED fault output signal is generated only once for certain fault type. If, for example, open fault occurs, new

open fault does not cause the FAULT pin to be pulled down uless chip is reset by setting EN pin low and high

again. The faults will be seen in the register however. If LED fault is detected, the string which created the fault is

no longer used for adjusting the boost voltage. Otherwise the LP8543 operates as normally.

Note: Due to the nature of fault detection it is possible to generate false faults during startup etc. conditions.

Therefore when fault is detected it is recommended to read the fault/status register twice to make sure that the

first fault is real. If the second reading gives the same result then the fault is real.

Under-Voltage Detection

seen in the following table:

Table 11. Under-Voltage Detection Thresholds

UVLO_THR

Threshold (V)

0

6

1

3

Under voltage detection is always on. When under voltage is detected the LED outputs and boost will shutdown,

Fault pin will be pulled down (open drain output) and corresponding fault bit is set in status register. Fault can be

reset by reading the status register. LEDs and boost will start again when the voltage has increased above the

threshold level. Hysteresis is implemented to threshold level to avoid continuous triggering of fault when

threshold is reached.

Note: Due to the nature of fault detection it is possible to generate false faults during startup etc. conditions.

Therefore when fault is detected it is recommended to read the fault/status register twice to make sure that the

first fault is real. If the second reading gives the same result then the fault is real.

Over-Current Detection

LP8543 has detection for too high loading on the boost converter. When over current fault is detected the

LP8543 will shut down and set the fault flag.

Thermal Shutdown

If the LP8543 reaches thermal shutdown temperature (150°C) the LED outputs and boost will shut down to

protect it from damage. Also the fault pin will be pulled down to indicate the fault state. Device will activate again

when temperature drops below 130°C.

SMBus/I

Interface Bus Overview

registers on the device. This protocol uses a two-wire interface for bidirectional communications between the IC's

connected to the bus. The two interface lines are the Serial Data Line (SDA), and the Serial Clock Line (SCL /

SCLK). These lines should be connected to a positive supply, via a pull-up resistor and remain HIGH even when

the bus is idle.

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