CAT4137 datasheet(13/16 Pages) ONSEMI

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CAT4137

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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 24 V. 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 10 mW.

In low power mode, the input supply current will typically

drop to 2 mA. An internal clamping circuit will limit the

subsequent output voltage to approximately 29 V. 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).

Figure 31. Open LED Protection

Figure 32. Open LED Power−up Waveforms

Figure 33. Open LED Supply Current vs. VIN

VIN

CAT4137

(Central CMDSH2−3)

1 μF

0.22 μF

15 W

GND

22 μH

OFF

INPUT VOLTAGE (V)

5.0

4.5

3.5

3.0

2.5

1.0

1.5

2.0

2.5

4.0

VFB = 300 mV

SHDN

VIN

VOUT

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