®
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
SYNC
1
RCT
2
TIMING
25V
DC-LIM
15
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.
V
CC
8
VREF
4
DC
3
+
-
T
DIS
Vref
+
15V/10V
-
PWM UVLO
9
V
C
DIS
2.5V
13V
BLANKING
S
R
PWM
OVER CURRENT
ISEN
13
+
-
FAULT
SOFT-START
SS
1.2V
7
August 2001
+
10
OUT
Q
VREF OK
CLK
DIS
-
14
VREF
11
16
PGND
ST-BY
STAND-BY
+
E/A
2.5V
2R
1V
R
12
SGND
6
COMP
-
5
VFB
D97IN725A
1/23
L5991 - L5991A
ABSOLUTE MAXIMUM RATINGS
Symbol
V
CC
I
OUT
Parameter
Supply Voltage (I
CC
< 50mA) (*)
Output Peak Pulse Current
Analog Inputs & Outputs (6,7)
Analog Inputs & Outputs (1,2,3,4,5,15,14, 13, 16)
Power Dissipation @ T
amb
= 70°C (DIP16)
@ T
amb
= 50°C (SO16)
Junction Temperature, Operating Range
Storage Temperature, Operating Range
Value
selflimit
1.5
-0.3 to 8
-0.3 to 6
1
0.83
-40 to 150
-55 to 150
Unit
V
A
V
V
W
W
°C
°C
P
tot
T
j
T
stg
(*) maximum package power dissipation limits must be observed
PIN CONNECTION
SYNC
RCT
DC
VREF
VFB
COMP
SS
V
CC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
ST-BY
DC-LIM
DIS
ISEN
SGND
PGND
OUT
V
C
THERMAL DATA
Symbol
R
th j-amb
Parameter
Thermal Resistance Junction -Ambient
(DIP16)
Thermal Resistance Junction -Ambient
(SO16)
Value
80
120
Unit
°C/W
°C/W
PIN FUNCTIONS
N.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Name
SYNC
RCT
DC
VREF
VFB
COMP
SS
V
CC
V
C
OUT
PGND
SGND
ISEN
DIS
DC-LIM
ST-BY
Function
Synchronization. A synchronization pulse terminates the PWM cycle and discharges Ct
Oscillator pin for external C
T
, R
A
, R
B
components
Duty Cycle control
5.0V +/-1.5% reference voltage @ 25°C
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
Standby. Connect a resistor to RCT. Connect to VREF or floating if not used.
2/23
L5991 - L5991A
ELECTRICAL CHARACTERISTICS
(V
CC
= 15V; T
j
= 0 to 105°C; R
T
= 13.3kΩ (*) C
T
= 1nF;
unless otherwise specified.)
Symbol
Parameter
REFERENCE SECTION
V
REF
Output Voltage
Line Regulation
Load Regulation
T
S
Temperature Stability
Total Variation
Short Circuit Current
I
OS
Power Down/UVLO
OSCILLATOR SECTION
Initial Accuracy
Test Condition
T
j
= 25°C; I
O
= 1mA
V
CC
= 12 to 20V; T
j
= 25°C
I
O
= 1 to 10mA; T
j
= 25°C
Line, Load, Temperature
Vref = 0V
V
CC
= 6V; I
sink
= 0.5mA
pin 15 = Vref; T
j
= 25°C; V
comp
= 4.5V
pin 15 = Vref; V
CC
= 12 to 20V
V
comp
= 4.5V
pin 15 = Vref; V
CC
= 12 to 20V
V
comp
= 2V
pin 3 = 0,7V, pin 15 = V
REF
pin 3 = 0.7V, pin 15 = OPEN
pin 3 = 3.2V, pin 15 = V
REF
pin 3 = 3.2V, pin 15 = OPEN
pin 3 = 2.79V, pin 15 = OPEN
Min.
4.925
Typ.
5.0
2.0
2.0
0.4
5.0
0.2
95
93
46.5
100
100
50
Max.
5.075
10
10
5.130
150
0.5
105
107
53.5
0
0
47
93
75
2.8
0.75
Unit
V
mV
mV
mV/°C
V
mA
V
kHz
kHz
kHz
%
%
%
%
%
V
V
µA
V
dB
dB
V
V
mA
mA
MHz
V/µs
µA
V
ns
V/V
V
µA
µA
V
V
ns
1.0
10
9
10.5
10
13
2
V
V
V
V
µA
4.80
30
Duty Cycle
Duty Cycle Accuracy
Oscillator Ramp Peak
Oscillator Ramp Valley
ERROR AMPLIFIER SECTION
Input Bias Current
V
I
Input Voltage
Open Loop Gain
G
OPL
SVR
Supply Voltage Rejection
Output Low Voltage
V
OL
V
OH
Output High Voltage
Output Source Current
I
O
Output Sink Current
Unit Gain Bandwidth
Slew Rate
S
R
PWM CURRENT SENSE SECTION
Input Bias Current
I
b
I
S
Maximum Input Signal
Delay to Output
Gain
Fault Threshold Voltage
V
t
SOFT START SECTION
SS Charge Current
I
SSC
I
SSD
SS Discharge Current
SS Saturation Voltage
V
SSSAT
V
SSCLAMP
SS Clamp Voltage
LEADING EDGE BLANKING
Internal Masking Time
OUTPUT SECTION
Output Low Voltage
V
OL
Output High Voltage
V
OH
V
OUT CLAMP
Output Clamp Voltage
Collector Leakage
80
3.0
0.9
0.2
2.5
90
85
6
1.3
6
4
8
3
1.0
70
3
1.2
20
10
7
100
85
3.2
1.05
3.0
2.58
V
FB
to GND
V
COMP
= V
FB
V
COMP
= 2 to 4V
V
CC
= 12 to 20V
I
sink
= 2mA
I
source
= 0.5mA, V
FB
= 2.3V
V
COMP
> 4V, V
FB
= 2.3V
V
COMP
= 1.1V, V
FB
= 2.7V
2.42
60
1.1
5
0.5
2
1.7
2.5
I
sen
= 0
V
COMP
= 5V
0.92
2.85
1.1
15
1.08
100
3.15
1.3
26
15
0.6
T
j
= 25°C
VSS = 0.6V T
j
= 25°C
DC = 0%
14
5
I
O
= 250mA
I
O
= 20mA; V
CC
= 12V
I
O
= 200mA; V
CC
= 12V
I
O
= 5mA; V
CC
= 20V
V
CC
= 20V V
C
= 24V
20
(*) R
T
= R
A
//R
B
, R
A
= R
B
= 27kΩ, see Fig. 23.
3/23
L5991 - L5991A
ELECTRICAL CHARACTERISTICS
(continued.)
Symbol
Parameter
OUTPUT SECTION
Fall Time
Rise Time
UVLO Saturation
SUPPLY SECTION
Startup voltage
V
CCON
V
CCOFF
V
hys
I
S
I
op
I
q
Minimum Operating
Voltage
UVLO Hysteresis
Start Up Current
Operating Current
Quiescent Current
Test Condition
C
O
= 1nF
C
O
= 2.5nF
C
O
= 1nF
C
O
= 2.5nF
V
CC
= V
C
= 0 to V
CCON;
I
sink
= 10mA
L5991
L5991A
L5991
L5991A
L5991
L5991A
Before Turn-on at:
V
CC
= V
C
= V
CCON
-0.5V
C
T
= 1nF, R
T
= 13.3kΩ, C
O
=1nF
(After turn on), CT = 1nF,
R
T
= 13.3kΩ, C
O
=0nF
I
8
= 20mA
I
ST-BY
= 2mA
V
comp
Falling
V
comp
Rising
Master Operation
I
SOURCE
= 0.8mA
Vclock = 3.5V
Slave Operation
Low Level
High Level
VSYNC = 3.5V
14
7.8
9
7
4.5
0.5
40
Min.
Typ.
20
35
50
70
Max.
60
100
1.0
15
8.4
10
7.6
5
0.8
75
9
7.0
21
25
45
2.5
4.0
16
9
11
8.2
Unit
ns
ns
ns
ns
V
V
V
V
V
V
V
µA
mA
mA
V
mV
V
V
120
13
10
30
V
Z
Zener Voltage
STANDBY FUNCTION
V
REF
-V
ST-BY
Standby Threshold
V
T1
SYNCHRONIZATION SECTION
V
1
I
1
V
1
Clock Amplitude
Clock Source Current
Sync Pulse
4
3
7
1
V
mA
V
V
mA
V
V
µA
µA
Sync Pulse Current
I
1
OVER CURRENT PROTECTION
Fault Threshold Voltage
V
t
DISABLE SECTION
Shutdown threshold
Input Bias Current
Quiescent current After
I
qSH
Disable
3.5
0.5
1.1
2.4
-1
1.2
2.5
330
1.3
2.6
1
V
pin14
= 0 to 3V
V
CC
= 15V
Figure 1. L5991 - Quiescent current vs. input
voltage.
(X = 7.6V and Y= 8.4V for L5991A)
Iq [m A ]
30
Figure 2. L5991 - Quiescent current vs. input
voltage (after disable).
(X = 7.6V and Y= 8.4V for L5991A)
Iq [µ A ]
350
20
8
6
4
0 .2
0 .1 5
0 .1
0 .0 5
0
0
4
V 1 4 = 0 , P in 2 = o p e n
T j = 2 5 °C
300
250
200
150
100
V 1 4 = V ref
T j = 2 5 °C
X
Y
X
Y
50
0
0
4
8
8
12
16
V c c [V ]
20
24
28
12
16
V c c [V ]
20
24
4/23
L5991 - L5991A
Figure 3. Quiescent current vs. input voltage.
Iq [m A ]
9 .0
V 14 = 0, V 5 = V ref
R t = 4.5Koh m ,T j = 25 °C
8 .5
1 M hz
5 00K hz
3 00K hz
1 00K hz
Figure 4. Quiescent current vs. input voltage
and switching frequency.
Iq [m A ]
36
30
24
1 M Hz
C o = 1 nF, T j = 25°C
D C = 0%
8 .0
18
5 00 K H z
12
7 .5
3 00 K H z
1 00 K H z
6
0
8
10
12
14
16
18
V c c [V ]
20
22
24
7 .0
8
10
12
14
16
V cc [V ]
18
20
22
Figure 5. Quiescent current vs. input voltage
and switching frequency.
Iq [mA]
36
Co = 1nF, Tj = 25°C
Figure 6. IC Consumption vs. Temperature.
[mA]
100
Operating current
Vcc =15V, after turn-on
RT=13.3kΩ, CT=1nF
DC=75%, Co=1nF
Quiescent current
Vcc =15V, after turn-on
RT=13.3 kΩ, CT=1nF
DC = 0
30
24
18
12
DC = 100%
1MHz
10
500KHz
1
300KHz
100KHz
0.1
6
0
8
10
12
14
16
Vcc [V]
18
20
22
0.01
-50
Start-up current
Vc=Vcc= Vccon-0.5V, before turn-on
-25
0
25
50
75
100
125
150
Junction temperature [˚C]
Figure 7. Reference voltage vs. load current.
Vref [V]
5.1
Figure 8. Vref vs. junction temperature.
Vref [V])
5.1
5.05
Vcc=15V
Tj = 25°C
5.05
Vcc = 15V
Iref = 1mA
5
5
4.95
4.95
4.9
0
5
10
Iref [mA]
15
20
25
4.9
-50
-25
0
25
50
Tj (°C)
75
100
125
150
5/23
