NCP1237 datasheet(29/34 Pages) ONSEMI

Part #	NCP1237

Description	Fixed Frequency Current Mode Controller for Flyback Converters

PDF	34 Pages

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Manufacturer	ONSEMI [ON Semiconductor]

Direct Link	http://www.onsemi.com

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29 / 34 page

NCP1237

http://onsemi.com

Figure 27. Latch−off Function Timing Diagram

time

Internal Latch Signal

time

VCC

time

DRV

VCC(on)

VCC(min)

Latch signal

high during

pre-start phase

Noise spike

ignored

(tLatch blanking)

Start-up

initiated by

VCC(on)

Switching

allowed (no

latch event)

Latch-off

Temperature shutdown

The die includes a temperature shutdown protection with

a turn−off threshold guaranteed between 140

°C and 160°C,

and a typical hysteresis of 30

°C. When the temperature rises

above the high threshold, the controller stops switching

instantaneously, the HV current source is turned off, and the

internal logic state is reset.

When the temperature falls below the low threshold, the

HV startup current source is enabled, and a regular startup

sequence takes place.

NCP1237 Datasheet(PDF) 29 Page - ON Semiconductor