Copyright © 2000

Rev. 1.4

4/00

FOR FUR THER INFORMA TION CALL (714) 898-8121

1

OF

SG1844/SG1845 Series

DESCRIPTION

KEY FEA TURES

s OPTIMIZED FOR OFF-LINE CONTROL

s LOW START-UP CURRENT (<1mA)

s AUTOMATIC FEED FORWARD

COMPENSATION

s TRIMMED OSCILLATOR DISCHARGE

CURRENT

s PULSE-BY-PULSE CURRENT LIMITING

s ENHANCED LOAD RESPONSE

CHARACTERISTICS

s UNDER-VOLTAGE LOCKOUT WITH 6V

HYSTERESIS (SG1844 only)

s DOUBLE PULSE SUPPRESSION

s HIGH-CURRENT TOTEM-POLE OUTPUT

s INTERNALLY TRIMMED BANDGAP

REFERENCE

s 500kHz OPERATION

s UNDERVOLTAGE LOCKOUT

SG1844 - 16 volts

SG1845 - 8.4 volts

s LOW SHOOT-THROUGH CURRENT <75mA

OVER TEMPERATURE

The SG1844/45 family of control ICs

provides all the necessary features to

implement off-line fixed frequency,

current-mode switching power supplies

with a minimum number of external

components. Current-mode architecture

demonstrates improved line regulation,

improved load regulation, pulse-by-

pulse current limiting and inherent

protection of the power supply output

switch.

The bandgap reference is trimmed to

±1% over temperature. Oscillator

discharge current is trimmed to less than

±10%. The SG1844/45 has under-

voltage lockout, current-limiting circuitry

PRODUCT HIGHLIGHT

P A CKAGE O RDER I NFORMA TION

T

0 to 70

SG3844M

SG3844N

SG3844DM

SG3844D

SG3844Y

SG3844J

—

—

SG3845M

SG3845N

SG3845DM

SG3845D

SG3845Y

SG3845J

—

—

-25 to 85

SG2844M

SG2844N

SG2844DM

SG2844D

SG2844Y

SG2844J

—

—

SG2845M

SG2845N

SG2845DM

SG2845D

SG2845Y

SG2845J

—

—

-55 to 125

—

—

—

—

SG1844Y

SG1844J

—

SG1844L

—

—

—

—

SG1845Y

SG1845J

—

SG1845L

MIL-STD/883

—

—

—

—

SG1844Y/883B SG1844J/883B

—

SG1844L/883B

—

—

—

—

SG1845Y/883B SG1845J/883B

—

SG1845L/883B

DESC

—

—

—

—

SG1844Y/DESC SG1844J/DESC

SG1844F/DESC SG1844L/DESC

—

—

SG1845Y/DESC SG1845J/DESC

SG1845F/DESC SG1845L/DESC

HIGH RELIABILITY FEATURES

s AVAILABLE TO MIL-STD-883B

s LINFINITY LEVEL "S" PROCESSING AVAILABLE

Note: All surface-mount packages are available in Tape & Reel.

and start-up current of less than 1mA.

The totem-pole output is optimized to

drive the gate of a power MOSFET. The

output is low in the off state to provide

direct interface to an N-channel device.

Both operate up to a maximum duty

cycle range of zero to <50% due to an

internal toggle flip-flop which blanks the

output off every other clock cycle.

The SG1844/45 is specified for

operation over the full military ambient

temperature range of -55°C to 125°C.

The SG2844/45 is specified for the

industrial range of -25°C to 85°C, and

the SG3844/45 is designed for the

commercial range of 0°C to 70°C.

Plastic DIP

8-pin

M

Plastic DIP

14-pin

N

Plastic SOIC

8-pin

DM

Plastic SOIC

14-pin

D

Ceramic DIP

8-pin

Y

Ceramic DIP

14-pin

J

Cer. Flatpack

10-pin

F

Ceramic LCC

20-pin

L

AC

INPUT

SG3844

R

ST

I

ST

V

CC