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XC9133

Series

SYMBOL

VALUE

PART NUMBER

MANUFACTURER

L

22

μH

VLF3010A-220MR

TDK

XBS053V15R

(*2)

TOREX

SBD

(*1)

-

MA2Z720

PANASONIC

4.7

μF

JMK107BJ475MA-B

TAIYO YUDEN

(*3)

0.22

μF

TMK107BJ224KA-B

TAIYO YUDEN

The series consists of a reference voltage source, ramp wave circuit, error amplifier, PWM comparator, phase

compensation circuit, Lx overvoltage limit circuit, N-channel MOS driver transistor, current limiter circuit and others.

Phase compensation is performed on the resulting error amplifier output, to input a signal to the PWM comparator to

determine the turn-on time during switching.

The PWM comparator compares, in terms of voltage level, the signal from

the error amplifier with the ramp wave from the ramp wave circuit, and delivers the resulting output to the N-channel MOS

driver transistor to cause the Lx pin to output a switching duty cycle.

This process is continuously performed to ensure

stable output voltage. The current feedback circuit detects the N-channel MOS driver transistor's current for each

switching operation, and modulates the error amplifier output signal.

This enables a stable feedback loop even when a

low ESR capacitor, such as a ceramic capacitor, is used, ensuring stable output voltage.

<Reference Voltage Source>

The reference voltage source provides the reference voltage to ensure stable output voltage of the IC.

<Ramp Wave Circuit>

The ramp wave circuit determines switching frequency.

The 1MHz (TYP.) of frequency is fixed internally.

Clock pulses generated in this circuit are used to produce ramp waveforms needed for PWM operation.

<Error Amplifier>

The error amplifier is designed to monitor output voltage.

The amplifier compares the reference voltage with the FB pin

voltage.

When a feed-back voltage becomes lower than the reference voltage, an output voltage of the error amplifier is

increased.

Gain and frequency characteristics of the error amplifier output are fixed internally as an optimize signal.

■TYPICAL APPLICATION CIRCUITS

●XC9133B02A

■EXTERNAL COMPONENTS

NOTE:

*1: Please use a Schottky barrier diode (SBD) with a low junction capacitance.

*3: Use ceramic capacitors processing a low temperature coefficient.

■OPERATIONAL EXPLANATION