AP2014/A

Synchronous PWM Controller

Anachip Corp

www.anachip.com.tw

Rev. 1.2 Nov 29, 2005

10/12

Function Descriptions

Introduction

The AP2014 is a fixed frequency, voltage mode

synchronous controller and consists of a precision

reference voltage, an error amplifier, an internal

oscillator, a PWM comparator, 0.5A peak gate driver,

soft-start

and

shutdown

circuits

(see

Block

Diagram).

The output voltage of the synchronous converter is

set and controlled by the output of the error amplifier;

this is the amplified error signal from the sensed

output voltage and the reference voltage.

This voltage is compared to a fixed frequency linear

sawtooth ramp and generates fixed frequency

pulses of variable duty-cycle, which drives the two

N-channel external MOSFETs.The timing of the IC

is provided through an internal oscillator circuit

which uses on-chip capacitor to set the oscillation

frequency to 200 KHz (400 KHz for “A” version).

Soft-Start

The AP2014 has a programmable soft-start to

control the output voltage rise and limit the current

surge at the start-up. To ensure correct start-up, the

rise

above

their

threshold

(3.3V

and

4.2V

respectively) and generates the Power On Reset

(POR) signal.

Soft-start function operates by

sourcing an internal current to charge an external

capacitor to about 3V. Initially, the soft-start function

clamps the E/A’s output of the PWM converter. As

the charging voltage of the external capacitor ramps

up, the PWM signals increase from zero to the point

the feedback loop takes control.

Short-Circuit Protection

The outputs are protected against the short circuit.

The AP2014 protects the circuit for shorted output

by sensing the output voltage (through the external

resistor divider). The AP2014 shuts down the PWM

signals, when the output voltage drops below 0.6V

(0.4V for AP2014A).

The

AP2014

also

protects

the

output

from

over-voltaging when the control FET is shorted.

This is done by turning on the sync FET with the

maximum duty cycle.

Under-Voltage Lockout

The under-voltage lockout circuit assures that the

MOSFET driver outputs remain in the off state

whenever the supply voltage drops below set

3.3V and 4.2V respectively. Normal operation

IC Quiescent Power Dissipation

Power dissipation for IC controller is a function of

applied voltage, gate driver loads and switching

frequency. The IC's maximum power dissipation

occurs when the IC operating with single 12V supply

voltage (Vcc=12V and Vc 24V) at 400KHz switching

frequency and maximum gate loads.

Page 8 show voltage vs. current, when the

gate drivers loaded with 1500pF capacitors. The IC's

power dissipation results to an excessive

temperature rise. This should be considered when

using AP2014A for such application.

Marking Information

(Top View)

SOP-8L/PDIP-8L

AP2014 X

YY WW X

Logo

Part No.

ID code: internal

Year: "01" =2001

"02" =2002

Xth week: 01~52

5

8

4

1

AP2014 : 200KHz (OSC)

AP2014A : 400KHz (OSC)