ML4823MJ Micro Linear, ML4823MJ Datasheet

ML4823MJ

Manufacturer Part Number

ML4823MJ

Description

High Frequency Power Supply Controller

Manufacturer

Micro Linear

Datasheet

1.ML4823MJ.pdf (9 pages)

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GENERAL DESCRIPTION

The ML4823 High Frequency PWM Controller is an IC

controller optimized for use in Switch Mode Power

Supply designs running at frequencies to 1MHz.

Propagation delays are minimal through the comparators

and logic for reliable high frequency operation while slew

rate and bandwidth are maximized on the error amplifier.

This controller is designed for single-ended applications

using voltage or current mode and provides for input

voltage feed forward.

A 1V threshold current limit comparator provides cycle-

by-cycle current limit and exceeding a 1.4V threshold

initiates a soft-start cycle. The soft start pin doubles as a

maximum duty cycle clamp. All logic is fully latched to

provide jitter-free operation and prevent multiple pulsing.

An under-voltage lockout circuit with 800mV of hysteresis

assures low startup current and drives the outputs low

during fault conditions.

This controller is an improved second source for the

UC3823 controller; however, the ML4823 includes

features not found on the 3823. These features are set in

italics .

BLOCK DIAGRAM

RAMP

E/A OUT

INV

SOFT START

LIM

1.4V

/S.D.

REF

–

1.25V

ERROR

AMP

–

OSC

(Pin Configuration Shown for 16-Pin Version)

High Frequency Power Supply Controller

–

COMP

V+

–

FEATURES

Practical operation at switching frequencies to 1.0MHz

High current (2A peak) totem pole output

Wide bandwidth error amplifier

Fully latched logic with double pulse suppression

Pulse-by-pulse current limiting

Soft start and max. duty cycle control

Under voltage lockout with hysteresis

5.1V trimmed bandgap reference

Low start-up current (1.1mA)

Pin compatible improved replacement for UC3823

Fast shut down path from current limit to output

Soft start latch ensures full soft start cycle

Outputs pull low for undervoltage lockout

*Some Packages Are Obsolete

5.1V

UNDER

VOLTAGE

LOCKOUT

–

ENABLE

REF

–

GEN

INTERNAL

BIAS

ML4823*

POWER GND

SIGNAL GND

CLOCK OUT

POWER V

5.1V V

OUTPUT

May 1997

REF

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ML4823MJ Summary of contents

Page 1

High Frequency Power Supply Controller GENERAL DESCRIPTION The ML4823 High Frequency PWM Controller controller optimized for use in Switch Mode Power Supply designs running at frequencies to 1MHz. Propagation delays are minimal through the comparators and logic ...

Page 2

ML4823 PIN CONFIGURATION ML4823 16-PIN DIP (P16) 16-PIN SOIC (S16W) INV E/A OUT 3 14 CLOCK RAMP TOP VIEW PIN ...

Page 3

ABSOLUTE MAXIMUM RATINGS Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. Supply Voltage ( .......................................... 30V C ...

Page 4

ML4823 ELECTRICAL CHARACTERISTICS PARAMETER ERROR AMPLIFIER (Continued) CMRR PSRR Output Sink Current Output Source Current Output High Voltage Output Low Voltage Unity Gain Bandwidth Slew Rate PWM COMPARATOR RAMP Bias Current Duty Cycle Range E/A OUT Zero DC Threshold Delay ...

Page 5

FUNCTIONAL DESCRIPTION OSCILLATOR The ML4823 oscillator charges the external capacitor (C with a current (I ) equal to 3/R . When the capacitor SET SET voltage reaches the upper threshold (Ramp Peak), the comparator changes state and the capacitor discharges ...

Page 6

ML4823 ERROR AMPLIFIER The ML4823 error amplifier is a 5.5MHz bandwidth 12V/ s slew rate op-amp with provision for limiting the positive output voltage swing (Output Inhibit line) for ease in implementing the soft start function ...

Page 7

SOFT START AND CURRENT LIMIT The ML4823 employs two current limits. When the voltage at I /SD exceeds the I REF threshold on I LIM LIM REF, the outputs are immediately shut off and the cycle is terminated for the ...

Page 8

PHYSICAL DIMENSIONS 16 PIN 0.02 MIN (0.50 MIN) (4 PLACES) 0.170 MAX (4.32 MAX) 0.125 MIN (3.18 MIN) 0.385 - 0.395 (8.89 - 10.03) 0.350 - 0.356 (8.89 - 9.04) 1 PIN 1 ID 0.042 - 0.048 ...

Page 9

... ML4823CP ML4823CQ ML4823CS ML4823IP ML4823IS ML4823MJ © Micro Linear 1997 is a registered trademark of Micro Linear Corporation Micro Linear Products described in this document may be covered by one or more of the following patents, U.S.: 4,897,611; 4,964,026; 5,027,116; 5,281,862; 5,283,483; 5,418,502; 5,508,570; 5,510,727; 5,523,940; 5,546,017; 5,559,470; 5,565,761; 5,592,128; 5,594,376; Japan: 2598946; 2619299. Other patents are pending. ...

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