L5991_01 Datasheet, PDF (1/23 Pages) STMicroelectronics – PRIMARY CONTROLLER WITH STANDBY

L5991
®
L5991A
PRIMARY CONTROLLER WITH STANDBY
CURRENT-MODE CONTROL PWM
SWITCHING FREQUENCY UP TO 1MHz
LOW START-UP CURRENT (< 120µA)
HIGH-CURRENT OUTPUT DRIVE SUITABLE
FOR POWER MOSFET (1A)
FULLY LATCHED PWM LOGIC WITH DOU-
BLE PULSE SUPPRESSION
PROGRAMMABLE DUTY CYCLE
100% AND 50% MAXIMUM DUTY CYCLE LIMIT
STANDBY FUNCTION
PROGRAMMABLE SOFT START
PRIMARY OVERCURRENT FAULT DETEC-
TION WITH RE-START DELAY
PWM UVLO WITH HYSTERESIS
IN/OUT SYNCHRONIZATION
LATCHED DISABLE
INTERNAL 100ns LEADING EDGE BLANK-
ING OF CURRENT SENSE
PACKAGE: DIP16 AND SO16
DESCRIPTION
This primary controller I.C., developed in BCD60II
technology, has been designed to implement off
BLOCK DIAGRAM
MULTIPOWER BCD TECHNOLOGY
DIP16
SO16
ORDERING NUMBERS: L5991/L5991A (DIP16)
L5991D/L5991AD (SO16)
line or DC-DC power supply applications using a
fixed frequency current mode control.
Based on a standard current mode PWM control-
ler this device includes some features such as
programmable soft start, IN/OUT synchronization,
disable (to be used for over voltage protection and
for power management), precise maximum Duty
Cycle Control, 100ns leading edge blanking on
current sense, pulse by pulse current limit, over-
current protection with soft start intervention, and
Standby function for oscillator frequency reduction
when the converter is lightly loaded.
2
RCT
+
3
DC
-
14
DIS
-
DIS
+
2.5V
ISEN
SS
OVER CURRENT
13
+
-
1.2V
7
1V
SYNC
1
TIMING
T
DC-LIM
15
V_CC
8
25V
+
15V/10V -
Vref
PWM UVLO
VREF
4
9
V_C
BLANKING
PWM
FAULT
SOFT-START
2R
R
12
SGND
SQ
R
VREF OK
CLK
DIS
6
COMP
13V
10
OUT
VREF
STAND-BY
+
2.5V
E/A
-
11
PGND
16
ST-BY
5
VFB
D97IN725A
August 2001
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