REJ03D0835-0300 Rev.3.00 Jun 06, 2008

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M51995AP/AFP

Switching Regulator Control

REJ03D0835-0300

Rev.3.00

Jun 06, 2008

Description

M51995A is the primary switching regulator controller which is especially designed to get the regulated DC voltage

from AC power supply.

This IC can directly drive the MOS-FET with fast rise and fast fall output pulse.

Type M51995A has the functions of not only high frequency OSC and fast output drive but also current limit with fast

response and high sensibility so the true “fast switching regulator” can be realized.

It has another big feature of current protection to short and over current, owing to the integrated timer-type protection

circuit, if few parts are added to the primary side.

The M51995A is equivalent to the M51977 with externally re-settable OVP (over voltage protection) circuit.

Features

• 500 kHz operation to MOS FET

 Output current : ±2 A

 Output rise time 60 ns, fall time 40 ns

 Modified totempole output method with small through current

• Compact and light-weight power supply

 Small start-up current : 90 µA typ.

 Big difference between “start-up voltage” and “stop voltage” makes the smoothing capacitor of the power input

section small.

Start-up threshold 16 V, stop voltage 10 V

 Packages with high power dissipation are used to with-stand the heat generated by the gate-drive current of MOS

FET.

16-pin DIP, 20-pin SOP 1.5 W (at 25

°C)

• Simplified peripheral circuit with protection circuit and built-in large-capacity totempole output

 High-speed current limiting circuit using pulse-by-pulse method (Two system of CLM+pin, CLM−pin)

 Protection by intermittent operation of output over current : Timer protection circuit

 Over-voltage protection circuit with an externally re-settable latch (OVP)

 Protection circuit for output miss action at low supply voltage (UVLO)

• High-performance and highly functional power supply

 Triangular wave oscillator for easy dead time setting

Application

Feed forward regulator, fly-back regulator