L4990 Datasheet PDF - STMicroelectronics


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L4990
STMicroelectronics

Part Number L4990
Description PRIMARY CONTROLLER
Page 24 Pages

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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
-
+
2.5V
DIS
ISEN
SS
OVER CURRENT
13
+
-
1.2V
7
1V
SYNC
1
TIMING
T
DC-LIM
15
VCC
8
25V
16V/10V
+
-
Vref
PWM UVLO
VREF
4
9
VC
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
1/24



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L4990 - L4990A
ABSOLUTE MAXIMUM RATINGS
Symbol
VCC
IOUT
Ptot
Tj
Tstg
Parameter
Supply Voltage (ICC < 50mA) (*)
Output Peak Pulse Current
Analog Inputs & Outputs (6,7)
Analog Inputs & Outputs (1,2,3,4,5,15,14 13)
Power Dissipation @ Tamb = 70°C
Junction Temperature, Operating Range
Storage Temperature, Operating Range
(*) maximum package power dissipation limits must be observed
Value
selflimit
1.5
-0.3 to 8
-0.3 to 6
1
-25 to 125
-55 to 150
Unit
V
A
V
V
W
°C
°C
PIN CONNECTION
SYNC
RCT
DC
VREF
VFB
COMP
SS
VCC
1 16
2 15
3 14
4 13
5 12
6 11
7 10
89
D95IN197
THERMAL DATA
Symbol
Rth j-amb
Rth j-amb
Parameter
Thermal Resistance Junction to Ambient
Thermal Resistance Junction to Ambient
N.C.
DC-LIM
DIS
ISEN
SGND
PGND
OUT
VC
DIP16
SO16
Value
80
120
Unit
°C/W
°C/W
PIN FUNCTIONS
N. Name
1 SYNC
2 RCT
3 DC
4 VREF
5 VFB
6 COMP
7 SS
8 VCC
9 VC
10 OUT
11 PGND
12 SGND
13 ISEN
14 DIS
15 DC-LIM
16 NC
Fun ction
Synchronization. A synchronization pulse terminates the PWM cycle and discharges Ct
Oscillator pin for external Ct, Rt components
Duty Cycle control
5.0V +/-1.5% reference voltage
Error Amplifier Inverting input
Error Amplifier Output
Soft start pin for external capacitor Css
Supply for internal ”Signal” circuitry
Supply for Power section
High current totem pole output
Power ground
Signal ground
Current sense
Disable. It must never be left floating. Tie to SGND if not used.
Connecting this pin to Vref, DC is limited to 50%. If it is left floating or grounded no limitation is
imposed
Not connected
2/24



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L4990 - L4990A
ELECTRICAL CHARACTERISTICS (VCC = 15V; Tj = 0 to 70°C; unless otherwise specified.)
Symbol
Parameter
REFERENCE SECTION
VO Output Voltage
Line Regulation
Load Regulation
TS Temperature Stability
Total Variation
IOS Short Circuit Current
Power Down/UVLO
OSCILLATOR SECTION
Initial Accuracy
Accuracy
Initial Accuracy
Accuracy
Duty Cycle
Duty Cycle
Duty Cycle Accuracy
Oscillator Ramp Peak
Oscillator Ramp Valley
ERROR AMPLIFIER SECTION
Input Bias Current
VI Input Voltage
GOPL
Open Loop Gain
SVR
Supply Voltage Rejection
VOL Output Low Voltage
VOH Output High Voltage
IO Output Source Current
Output Sink Current
Unit Gain Bandwidth
SR Slew Rate
PWM CURRENT SENSE SECTION
Ib Input Bias Current
IS Maximum Input Signal
Delay to Output
Gain
SOFT START
ISSC SS Charge Current
ISSD SS Discharge Current
VSSSAT SS Saturation Voltage
VSSCLAMP SS Clamp Voltage
LEADING EDGE BLANKING
Internal Masking Time
Test Condition
Min. Typ. Max. Unit
Tj = 25°C; IO = 1mA
VCC = 12 to 20V
IO = 1 to 20mA
Line, Load, Temperature
Vref = 0V
VCC = 8.5V; Isink = 0.5mA
4.925 5.0 5.075 V
2.0 15 mV
5.0 20 mV
0.4 mV/°C
4.875 5.0 5.125 V
30 150 mA
0.2 0.5
V
Tj = 25°C; RT = 4.42k;
CT = 1nF; pin 15 Vref
285 300 315 kHz
RT = 4.42K; VCC = 12 to 20V; 279 300 321 kHz
CT = 1nF; pin 15 = Vref
Tj = 25°C; RT = 4.42K;
CT = 1nF; pin 15 OPEN
280 295 310 kHz
RT = 4.42K; VCC = 12 to 20V; 275 295 315 kHz
CT = 1nF; pin 15 OPEN
pin 3 = 0,7V, pin 15 = Vref
pin 3 = 0.7V, pin 15 = OPEN
0%
0%
RT = 4.42kCT = 1nF
pin 3 = 3.2V, pin 15 = Vref
pin 3 = 3.2V, pin 15 = OPEN
45
90
%
%
pin 3 = 2.02V, pin 15 = OPEN 37 40 43 %
3.0 V
1.0 V
VFB to GND
VCOMP = VFB
VCOMP = 2 to 4V
VCC = 12 to 20V
Isink = 2mA, VFB = 2.7V
Isou rce = 0.5mA, VFB = 2.3V
VCOMP > 4V, VFB = 2.3V
VCOMP = 1.1V, VFB = 2.7V
0.2 1.0 µA
2.42 2.5 2.58
V
60 90
dB
85 dB
1.1 V
56
V
0.5 1.3
mA
26
mA
24
MHz
8 V/µs
Isen = 0
VCOMP = 5V
3 15 µA
0.92 1.0 1.08
V
100 ns
2.85 3 3.15 V/V
VSS = 0.6V
DC = 0%
14 20 26 µA
200 µA
0.6 V
7V
100 ns
3/24



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L4990 - L4990A
ELECTRICAL CHARACTERISTICS (continued.)
Symbol
Parameter
OUTPUT SECTION
VOL Output Low Voltage
VOH Output High Voltage
VOUT CLAMP
Output Clamp Voltage
Collector Leakage
Fall Time
Rise Time
UVLO Saturation
SUPPLY SECTION
VCCON
Startup voltage
VCCOFF Minimum Operating Voltage
Vhys Voltage After Turn-on Hysteresis
IS Start Up Current
Iop Operating Current
Iq Quiescent Current
ISH Shutdown Current
VZ Zener Voltage
SYNCHRONIZATION SECTION
V1 Clock Amplitude
I1 Clock Source Current
V1 Sync Pulse
I1 Sync Pulse Current
OVER CURRENT PROTECTION
Vt Fault Threshold Voltage
DISABLE SECTION
Shutdown threshold
Test Condition
IO = 250mA
IO = 20mA; VCC = 12V
IO = 200mA; VCC = 12V
IO = 5mA; VCC = 20V
VCC = 20V VC = 24V
CO = 1nF
CO = 2.5nF
CO = 1nF
CO = 2.5nF
VCC = 0V to VCCON; Isink = 10mA
L4990
L4990A
L4990
L4990A
L4990
L4990A
Before Turn-on at:
VCC = VCCON - 0.5V
CT = 1nF, RT = 4.42k, CO =1nF
(After turn on), Co =0nF
CT = 1nF, RT = 4.42k,
I8 = 20mA
Master Operation
ISOURCE = 0.8mA
Vclock = 3.5V
Slave Operation
Low Level
High Level
VSYNC = 3.5V
Min.
10
9
15
7.8
9
7
5.5
0.5
100
100
21
4
3.5
0.8
1.1
2.4
Typ.
10.5
10
13
100
20
35
50
70
16
8.4
10
7.6
6
0.8
270
12
7.0
270
25
7
1.2
2.5
Max.
1.0
200
60
100
1.0
17
9
11
8.2
450
18
10
450
30
1
1.3
2.6
Unit
V
V
V
V
µA
ns
ns
ns
ns
V
V
V
V
v
V
v
µA
mA
mA
µA
V
V
mA
V
V
mA
V
V
FUNCTIONAL DESCRIPTION
The I.C. contains a standard PWM current mode
control section with improved performance with
respect to the UC384X family.
Enhanced features include start-up bias current
reduced to < 270µA (typ), improved E/A perform-
ance (4MHz B/W, 1.3mA Source Current, high-
slew rate) accurate 1MHz oscillator, and also re-
duced propagation delays in the critical path from
Current Sense to Output.
4/24
ADDITIONAL FEATURES
Soft Start (SS)
An external capacitor is charged by an internal
constant current source (20µA) to generate a SS
signal which clamps the E/A output
The SS pin doubles as a Fault Reset Delay func-
tion as described below.
Current Limit / Reset Delay
An internal high-speed current limit comparator




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