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BD8381EFV-M

LED Drivers for Automotive Light

ROHM Semiconductor 

BD8381EFV-M

Technical Note

●Operation in error circumstances of LED

① LED open detection

VCC

OUTH

SW

VOUT

FB

OUTH/OUTL

VOUT/OVP

LED OPEN

50m

V

0V

Switching Duty extends.

Switching stop

1.7V

OUTL

PWMOUT

FB

OPEN

Q1

FAIL2

LED open detection when VOVP≧1.7 and VFB≦50mV

（When it achieves the detection condition, the FP latch is done. ）

Fig.18

②LED short detection

VCC

OUTH

SW

OUTL

PWMOUT

RSENSE

VOUT

N

1

Short

Q1

VOUT

LEDR-LEDC

It gets down by LED1 step.

N

LEDR

1

0V

OUTH/OUTL

FAIL2

0.2V

fosc

Switching stop

△T=32770×fo1sc

It detects short, and after the timer of △T,

error is detected with FAIL2.

Fig.19

③ LED anode/cathode land GND short detection

VCC

RSENSE

OUTH

SW

VOUT

Short

to GND

VOUT

LED anode GND short

0V

FB 200mV

50mV

0V

Capacity dependence connected with CT

OUTL

PWMOUT

Fig.20

Q1

RSENSE

OUTH/OUTL

FAIL2

1

Switching stop

Timer operation of CT after GND

short detection.

FAIL1 becomes Hi? Low.

It detects short, and after the timer of △T,

error is detected with FAIL2.

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10/20

2011.04 - Rev.A

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