General Description

The MAX5021/MAX5022 current-mode PWM controllers

contain all the control circuitry required for the design

of wide input voltage range isolated power supplies.

These devices are well suited for use in universal input

(85VAC to 265VAC) off-line or telecom (-36VDC to

-72VDC) power supplies.

An undervoltage lockout (UVLO) circuit with large hys-

teresis coupled with low startup and operating current

reduce power dissipation in the startup resistor and

allow use of ceramic bypass capacitors. The 262kHz

switching frequency is internally trimmed to ±12%

accuracy; this allows the optimization of the magnetic

and filter components resulting in compact, cost-effec-

tive power supplies. The MAX5021 with 50% maximum

duty cycle and MAX5022 with 75% maximum duty

cycle are recommended for forward converters and fly-

back converters, respectively. The MAX5021/MAX5022

are available in 6-pin SOT23, 8-pin µMAX, and 8-pin

DIP packages and are rated for operation over the

-40°C to +85°C temperature range.

Applications

Universal Off-Line Power Supplies

Standby Power Supplies

Isolated Power Supplies

Isolated Telecom Power Supplies

Mobile Phone Chargers

Features

o Available in a Tiny 6-Pin SOT23 Package

o 50µA Typical Startup Current

o 1.2mA Typical Operating Current

o Large UVLO Hysteresis of 14V

o Fixed Switching Frequency of 262kHz ±12%

o 50% Maximum Duty Cycle Limit (MAX5021)

o 75% Maximum Duty Cycle Limit (MAX5022)

o 60ns Cycle-by-Cycle Current-Limit Response

Time

Current-Mode PWM Controllers for Isolated

Power Supplies

________________________________________________________________ Maxim Integrated Products

1

GND

NDRV

16

OPTO

5

CS

MAX5021

MAX5022

SOT23

TOP VIEW

2

34

NDRV

N.C.

N.C.

1

2

8

7

CS

GND

OPTO

PDIP/

µMAX

3

4

6

5

MAX5021

MAX5022

Pin Configuration

Ordering Information

MAX5021

MAX5022

OPTO

NDRV

CS

GND

Typical Operating Circuit

19-2066; Rev 1; 9/01

EVALUATION

KIT AVAILABLE

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

PART

MAX

DUTY

CYCLE

TEMP.

RANGE

PIN-

PACKAGE

TOP

MARK

MAX5021EUT

50%

-40

°C to +85°C 6 SOT23-6 AASQ

MAX5021EUA

50%

-40

°C to +85°C 8 µMAX

—

MAX5021EPA

50%

-40

°C to +85°C 8 PDIP

—

MAX5022EUT

75%

-40

°C to +85°C 6 SOT23-6 AASR

MAX5022EUA

75%

-40

°C to +85°C 8 µMAX

—

MAX5022EPA

75%

-40

°C to +85°C 8 PDIP

—

WARNING: The MAX5021/MAX5022 are designed to work

with high voltages. Exercise caution!