L4990 Datasheet, PDF (1/24 Pages) STMicroelectronics – PRIMARY CONTROLLER

L4990
®
L4990A
PRIMARY CONTROLLER
CURRENT-MODE CONTROL PWM
SWITCHING FREQUENCY UP TO 1MHz
LOW START-UP CURRENT < 0.45mA
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
PROGRAMMABLE SOFT START
PRIMARY OVERCURRENT FAULT DETEC-
TION WITH RE-START DELAY
PWM UVLO WITH HYSTERESIS
IN/OUT SYNCHRONIZATION
DISABLE LATCHED
INTERNAL 100ns LEADING EDGE BLANK-
ING OF CURRENT SENSE
PACKAGE: DIP16 AND SO16W
DESCRIPTION
This primary controller I.C., developed in BCD60II
technology, has been designed to implement off
BLOCK DIAGRAM
MULTIPOWER BCD TECHNOLOGY
DIP16
SO16W
ORDERING NUMBERS: L4990/L4990A(DIP16)
L4990D/L4990AD (SO16W)
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 as pro-
grammable soft start, IN/OUT synchronization,
disable (to be used for over voltage protection
and for power management), precise maximum
Duty Cycle Control, 100ns (typ) leading edge
blanking on current sense, pulse by pulse current
limit and overcurrent protection with soft start in-
tervention.
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
+
16V/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
2.5V
+
E/A
-
11
PGND
5
VFB
D98IN1002
July 1999
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