SG1844 Datasheet, PDF (1/12 Pages) Microsemi Corporation – CURRENT MODE PWM CONTROLLER

THE IN F I N I T E P O W E R OF IN N O VAT I O N
L I N D O C # : 1844
SG1844/SG1845 Series
CURRENT MODE PWM CONTROLLER
PRODUCTION DATA SHEET
DESCRIPTION
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
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.
PRODUCT HIGHLIGHT
TYPICAL APPLICATION OF SG3844 IN A FLYBACK CONVERTER
AC
INPUT
R_ST
I_ST
V_CC
SG3844
KEY FEATURES
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
HIGH RELIABILITY FEATURES
s AVAILABLE TO MIL-STD-883B
s LINFINITY LEVEL "S" PROCESSING AVAILABLE
T_A (°C)
M
Plastic DIP
8-pin
0 to 70
SG3844M
SG3845M
-25 to 85
SG2844M
SG2845M
—
-55 to 125
—
—
MIL-STD/883
—
—
DESC
PACKAGE ORDER INFORMATION
N
Plastic DIP
14-pin
DM
Plastic
8-pin
SOIC
D
Plastic SOIC
14-pin
Y
Ceramic DIP
8-pin
J
Ceramic DIP
14-pin
F
Cer. Flatpack
10-pin
L
Ceramic LCC
20-pin
SG3844N
SG3844DM
SG3844D
SG3844Y
SG3844J
—
—
SG3845N
SG3845DM
SG3845D
SG3845Y
SG3845J
—
—
SG2844N
SG2844DM
SG2844D
SG2844Y
SG2844J
—
—
SG2845N
SG2845DM
SG2845D
SG2845Y
SG2845J
—
—
—
—
—
SG1844Y
SG1844J
—
SG1844L
—
—
—
SG1845Y
SG1845J
—
SG1845L
—
—
—
SG1844Y/883B SG1844J/883B
—
SG1844L/883B
—
—
—
SG1845Y/883B SG1845J/883B
—
SG1845L/883B
—
—
—
SG1844Y/DESC SG1844J/DESC SG1844F/DESC SG1844L/DESC
—
—
SG1845Y/DESC SG1845J/DESC SG1845F/DESC SG1845L/DESC
Note: All surface-mount packages are available in Tape & Reel.
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Copyright © 2000
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1
Rev. 1.4 4/00