Datasheet

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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

♦ Available in a Tiny 6-Pin SOT23 Package

♦ 50µA Typical Startup Current

♦ 1.2mA Typical Operating Current

♦ Large UVLO Hysteresis of 14V

♦ Fixed Switching Frequency of 262kHz ±12%

♦ 50% Maximum Duty Cycle Limit (MAX5021)

♦ 75% Maximum Duty Cycle Limit (MAX5022)

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

Time

MAX5021/MAX5022

Current-Mode PWM Controllers for Isolated

Power Supplies

________________________________________________________________ Maxim Integrated Products 1

GND

NDRV

16OPTO

5 V

MAX5021

MAX5022

SOT23

TOP VIEW

NDRV

N.C.N.C.

GNDV

OPTO

PDIP/µMAX

MAX5021

MAX5022

Pin Configuration

Ordering Information

MAX5021

MAX5022

OUT

SUPPLY

OPTO NDRV

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!

Summary of content (11 pages)

PAGE 1
9-2066; Rev 1; 9/01 ABLE KIT AVAIL N IO T A U L EVA Current-Mode PWM Controllers for Isolated Power Supplies Features ♦ Available in a Tiny 6-Pin SOT23 Package An undervoltage lockout (UVLO) circuit with large hysteresis coupled with low startup and operating current reduce power dissipation in the startup resistor and allow use of ceramic bypass capacitors.
PAGE 2
MAX5021/MAX5022 Current-Mode PWM Controllers for Isolated Power Supplies ABSOLUTE MAXIMUM RATINGS VIN to GND .............................................................-0.3V to +30V VCC to GND ............................................................-0.3V to +13V NDRV to GND.............................................-0.3V to (VCC + 0.3V) CS, OPTO to GND ....................................................-0.3V to +6V NDRV Short-Circuit to GND........................................
PAGE 3
Current-Mode PWM Controllers for Isolated Power Supplies (VIN = +11V to +28V, VCS = 0, OPTO is unconnected, 10nF bypass capacitors at VIN and VCC, NDRV unconnected, TA = -40°C to +85°C, unless otherwise noted. Typical values are at VIN = +12V, TA = +25°C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 230 kHz OSCILLATOR Switching Frequency fSW Maximum Duty Cycle DMAX 262 290 MAX5021 50 51 MAX5022 75 76 5.5 V 6.2 7.
PAGE 4
Typical Operating Characteristics (continued) (VIN = 15V, TA = +25°C, unless otherwise noted.) 1.45 9.06 VIN = 28.0V VCS = 0 OPTO = UNCONNECTED 9.03 1.40 40 60 80 7.70 -40 -20 TEMPERATURE (°C) 40 60 80 -40 MEAN 600 -3σ 15 10 0 570 20 40 60 540 80 560 270 +3σ 265 MEAN 255 -3σ 580 600 620 640 245 660 -40 -20 CURRENT SENSE DELAY vs.
PAGE 5
Current-Mode PWM Controllers for Isolated Power Supplies PIN SOT23 PDIP µMAX NAME 1 8 CS FUNCTION Current Sense Connection for PWM Regulation and Overcurrent Protection. The current-limit comparator threshold is internally set to 0.6V. 2 7 GND Power-Supply Ground 3 6 NDRV External N-Channel MOSFET Gate Connection 4 3 VCC Gate Drive Supply. Internally regulated down from VIN. Decouple with a 10nF or larger capacitor to GND. 5 2 VIN IC Supply.
PAGE 6
MAX5021/MAX5022 Current-Mode PWM Controllers for Isolated Power Supplies L CENTRAL SEMICONDUCTOR CBR1-D100S AC L2 470µH 85VAC TO N 265VAC IN G C1 10µF 400V AC R8 1.2kΩ R1 360kΩ D1 RS = R1 + R2 C9 10µF 400V R2 360kΩ D1 250mA, 75V CENTRAL SEMICONDUCTOR CMPD914 C3 0.22µF 3T 8T R11 10Ω C4 150µF 6.3V +5V OUT VCC R10 10Ω C7 1000pF OPTO C5 0.01µF TEXAS INSTRUMENTS TLV431AIDBV VIN U1 C6 0.1µF R4 24.9kΩ 1% R3 1kΩ 1% OPTO C2 0.
PAGE 7
Current-Mode PWM Controllers for Isolated Power Supplies Undervoltage Lockout (UVLO) The device will attempt to start when VIN exceeds the UVLO threshold of 24V. During startup, the UVLO circuit keeps the CPWM comparator, ILIM comparator, oscillator, and output driver shut down to reduce current consumption (Functional Diagram). Once V IN reaches 24V, the UVLO circuit turns on both the CPWM and ILIM comparators, as well as the oscillator, and allows the output driver to switch.
PAGE 8
MAX5021/MAX5022 Current-Mode PWM Controllers for Isolated Power Supplies T1 VOUT RS C2 VIN VCC C3 MAX5022 OPTO GND NDRV CS -36VDC TO -72VDC IN Figure 4. -48VDC Input to +5V Output WARNING! DANGEROUS AND LETHAL VOLTAGES ARE PRESENT IN OFF-LINE CIRCUITS! USE EXTREME CAUTION IN THE CONSTRUCTION, TESTING, AND USE OF OFF-LINE CIRCUITS. Isolated Telecom Power Supply Figure 4 shows a -48VDC telecom power supply capable of generating an isolated +5V output.
PAGE 9
Current-Mode PWM Controllers for Isolated Power Supplies IN VIN VCC VCC REGULATOR REG_OK UVLO IN REFERENCE 1.25V 24V 10V GND VL (INTERNAL 5.25V SUPPLY) 6.2kΩ DRIVER S Q NDRV R OPTO CPWM 0.75V OSCILLATOR 262kHz* CS GND VOPWM VCS 0.
PAGE 10
Current-Mode PWM Controllers for Isolated Power Supplies 6LSOT.EPS MAX5021/MAX5022 Package Information PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, 8L uMAX/uSOP APPROVAL DOCUMENT CONTROL NO. 21-0036 10 REV.
PAGE 11
Current-Mode PWM Controllers for Isolated Power Supplies PDIPN.EPS Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.