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XC9147/XC9148 Series

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OPERATIONAL EXPLANATION

This IC consists of a reference voltage source, ramp wave circuit, error amplifier, PWM comparator, phase compensation circuit,

Nch driver FET, Pch synchronous switching FET and current limiter circuit.

XC9147/XC9148 J types

The main function of this IC is a current mode control step-up DC / DC converter that supports low ESR ceramic capacitors. By

adopting current mode control and increasing the oscillation frequency to a high frequency, the size of peripheral parts has been

reduced.

The current feedback circuit monitors the Nch driver FET’s turn-on current for each switching operation, and modulates the error

amplifier output signal to provide multiple feedback signals. This enables a stable feedback loop even when a low ESR capacitor,

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

Regarding to the parts required for operation, select the constants by referring to the part selection section. If a component that

is significantly different from this constant is used, proper phase compensation may not be obtained, and DC / DC may operate

unstable. Also, when using a capacitance other than a ceramic capacitor, use a low ESR capacitance. If a capacitor with a high

ESR is used, heat generation of the capacitor and unstable DC / DC operation may occur.

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Driver configuration / Load disconnection control (parasitic diode control)＞

A Pch FET is built-in on the High Side and an Nch FET is built-in on the Low Side.

In general Pch FETs, there is a parasitic diode with the source as the cathode and the drain as the anode, but the Pch FETs on

the High Side of the XC9147/XC9148 series control the polarity of the parasitic diode.

It is possible to disconnect the load between the input and output sides by controlling this parasitic diode during standby and

prevent reverse flow from the output side to the input side when external voltage is applied from the output side.

The control of the polarity of the parasitic diode depends on the types.

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VDD MAX＞

VDD MAX circuit compares the input voltage and the output voltage then it will select the higher one as the power supply for the

IC.

OSC

RAMP Wave

Generator

Phase

Compensation

Buffer

Driver

Vref with

Soft Start

Controller

Logic

Load disconnect

Controller

Error Amp.

PWM

comparator

CL

Discharge

CE

VOUT

GND

Lx

PWM/PFM

Controller Logic

BAT

VDD MAX

VOUT

VDD

VOUT

Current sense

Short-circuit protection

Latch Timer

UVLO

Thermal

Shutdown

RFB1

RFB2

FB

CFB

CE

Logic