Detailed Description

The MAX5070/MAX5071 current-mode PWM controllers

are designed for use as the control and regulation core of

flyback or forward topology switching power supplies.

These devices incorporate an integrated low-side driver,

adjustable oscillator, error amplifier (MAX5070A/

MAX5070B only), current-sense amplifier, 5V reference,

and external synchronization capability (MAX5071A/

clamp prevents overvoltage during startup.

Five different versions of the MAX5070/MAX5071 are

available. The MAX5070A/MAX5070B are the standard

versions with a feedback input (FB) and internal error

amplifier. The MAX5071A/MAX5071B include bidirection-

al synchronization (SYNC). This enables multiple

MAX5071A/MAX5071Bs to be connected and synchro-

nized to the device with the highest frequency. The

MAX5071C includes an ADV_CLK output, which pre-

cedes the MAX5071C’s drive output (OUT) by 110ns.

Figures 1, 2, and 3 show the internal functional diagrams

of the MAX5070A/MAX5070B, MAX5071A/MAX5071B,

and MAX5071C, respectively. The MAX5070A/

MAX5071A are capable of 100% maximum duty cycle.

The MAX5070B/MAX5071B/MAX5071C are designed to

limit the maximum duty cycle to 50%.

High-Performance, Single-Ended, Current-Mode

PWM Controllers

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11

UVLO

REFERENCE

2.5V

PREREGULATOR

5V

VOLTAGE-

DIVIDER

THERMAL

SHUTDOWN

EN-REF

BG

SNS

5V REGULATOR

VOLTAGE-

DIVIDER

8

7

26.5V

VREF

2.5V

VP

REG_OK

DELAY

S

R

Q

OSC

Q

6 OUT

ILIM

CPWM

1V

EN-DRV-BAR

R

2R

VEA

3

5

2

1

CS

GND

FB

COMP

CLK

MAX5070A/MAX5070B

VP

2.5V

16V/10V

100% MAX DUTY CYCLE (MAX5070A)

50% MAX DUTY CYCLE (MAX5070B)

Figure 1. MAX5070A/MAX5070B Functional Diagram