1

May 1997

ML4810

High Frequency Power Supply Controller

FEATURES

s

Integrating Soft Start Reset

s

High current (2A peak) dual totem pole outputs

s

s

5.1V

±2% trimmed bandgap reference

s

Under voltage lockout with 7V hysteresis

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Soft Start Reset Delay (ML4811)

s

Oscillator synchronization function (ML4811)

s

Soft Start latch ensures full soft start cycle

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Outputs pull low for undervoltage lockout

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Accurately controlled oscillator ramp discharge current

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GENERAL DESCRIPTION

The ML4810 and ML4811 High Frequency PWM

Controllers are optimized for use in Switch Mode Power

Supply designs running at frequencies to 1MHz. The

ML4810/11 contain a unique overload protection circuit

which helps to limit stress on the output devices and

reliably performs a soft-start reset. These controllers are

designed to work in either voltage or current mode and

provide for input voltage feed forward.

A 1.1V threshold current limit comparator provides a

cycle-by-cycle current limit. An integrating circuit

“counts” the number of times the 1.1V limit was reached.

A soft-start cycle is initiated if the cycle-by-cycle current

limit is repeatedly activated. A reset delay function is

provided on the ML4811.

These controllers are similar to the UC1825 controller,

* This part is End of Life as of August 1, 2000

however these controllers include many features not

** This part is Obsolete

found on the 1825. These features are set in

Italics.

+

–

OUT A

E/A OUT

RC (RESET)

RESET DELAY

INV

SOFT START

1.5V

CLOCK

1.1V

1.1V

5.1V

2.45V

1.1V

I(1)

3

× I(1)

V+

R

POWER GND

P

4V

R

TF.F.

OSC

S

UNDER

VOLTAGE

LOCKOUT

INTERNAL

BIAS

Q

ENABLE

9V

Q

Q

C

Q

S

RAMP

CLOCK

OUT B

POWER GND

GND

NI

6

7

SYNC

10

O.V.P./SHUTDOWN

11

8

3

2

1

12

9

R

Q

S

+

–

+

–

+

–

–

+

4

20

–

+

–

+

2.2V

COMP

ERROR

AMP

1.25V

I(1)

V+

I(1) =

3V

5

16

14

17

13

18

15

19