CAT4137TS datasheet(12/14 Pages) CATALYST

12 / 14 page

CAT4137

Doc. No. MD-5012 Rev. B

Characteristics subject to change without notice

OPEN LED PROTECTION

In the event of an “Open LED” fault condition, the

CAT4137 will continue to boost the output voltage

with maximum power until the output voltage reaches

approximately 24V. Once the output exceeds this

level, internal circuitry immediately places the device

into a very low power mode where the total input

power consumed is less than 10mW.

In low power mode, the input supply current will

typically drop to 2mA. An internal clamping circuit will

limit the subsequent output voltage to approximately

29V. This operating mode eliminates the need for any

external protection zener diode. This protection

scheme also fully protects the device against any

malfunction in the external Schottky diode (open-

circuit).

Open LED Protection

VIN

CAT4137

VIN

VOUT

(Central CMDSH2-3)

1µF

0.22µF

15Ω

SHDN

GND

22µH

OFF

VFB = 300mV

Open LED Power-up Waveforms

Open LED Supply Current vs. VIN

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

INPUT VOLTAGE [V]

CAT4137TS Datasheet(PDF) 12 Page - Catalyst Semiconductor

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