UC1524
UC2524
UC3524
15
7
6
16
V
IN
REFERENCE
REGULATOR
V
REF
+5V TO ALL
INTERNAL
CIRCUITRY
R
T
C
T
OSC
(RAMP)
3
OSC OUT
Q
Q
R
+5V
12
11
C
A
E
A
13
14
C
B
E
B
9
+5V
5
4
SENSE
+SENSE
C L
COMPENSATION
10k
1k
10
8
GROUND
(SUBSTRATE)
+5V
E A
1
2
INV INPUT
NI INPUT
COMPARATOR
SHUTDOWN
BLOCK DIAGRAM
DESCRIPTION
The UC1524, UC2524 and UC3524 incorporate on a single monolithic chip
all the functions required for the construction of regulating power supplies, in-
verters or switching regulators. They can also be used as the control element
for high-power-output applications. The UC1524 family was designed for
switching regulators of either polarity, transformer-coupled dc-to-dc convert-
ers, transformerless voltage doublers and polarity converter applications em-
ploying fixed-frequency, pulse-width modulation techniques. The dual
alternating outputs allow either single-ended or push-pull applications. Each
device includes an on-chip reference, error amplifier, programmable oscilla-
tor, pulse-steering flip-flop, two uncommitted output transistors, a high-gain
comparator, and current-limiting and shut-down circuitry. The UC1524 is
characterized for operation over the full military temperature range of -55C
to +125C. The UC2524 and UC3524 are designed for operation from -25C
to +85C and 0 to +70C, respectively.
Advanced Regulating Pulse Width Modulators
FEATURES
Complete PWM Power Control
Circuitry
Uncommitted Outputs for
Single-ended or Push-pull
Applications
Low Standby Current...8mA Typical
Interchangeable with SG1524,
SG2524 and SG3524, Respectively
SLUS180D - NOVEMBER 1999 - REVISED AUGUST 2002
2
UC1524
UC2524
UC3524
EA
CL
REF
REG
1
2
4
5
3
6
7
8
16
15
14
13
12
11
10
9
OSC
S/D
INV INPUT
NON INV
INPUT
OSC OUT
CLSENSE(+)
CLSENSE (-)
R
T
GND
C
T
V
REF
V
IN
E
B
C
B
C
A
E
A
S/D
COMP
CONNECTION DIAGRAM
ABSOLUTE MAXIMUM RATINGS (Note 1)
Supply Voltage, V
CC
(Notes 2 and 3) . . . . . . . . . . . . . . . . . 40V
Collector Output Current. . . . . . . . . . . . . . . . . . . . . . . . . 100mA
Reference Output Current . . . . . . . . . . . . . . . . . . . . . . . . 50mA
Current Through C
T
Terminal . . . . . . . . . . . . . . . . . . . . . . 5mA
Power Dissipation at T
A
= +25C (Note 4). . . . . . . . . . 1000mW
Power Dissipation at T
C
= +25C (Note 4). . . . . . . . . . 2000mW
Operating Junction Temperature Range . . . . 55C to +150C
Storage Temperature Range . . . . . . . . . . . . . 65C to +150C
Note 1: Over operating free-air temperature range unless oth-
erwise noted.
Note 2: All voltage values are with respect to the ground termi-
nal, pin 8.
Note 3: The reference regulator may be bypassed for operation
from a fixed 5V supply by connecting the V
CC
and ref-
erence output pins both to the supply voltage. In this
configuration the maximum supply voltage is 6V.
Note 4: Consult packaging section of databook for thermal lim-
itations and considerations of package.
RECOMMENDED OPERATING CONDITIONS
Supply Voltage, V
CC
. . . . . . . . . . . . . . . . . . . . . . . . . . 8V to 40V
Reference Output Current . . . . . . . . . . . . . . . . . . . . . 0 to 20mA
Current through C
T
Terminal . . . . . . . . . . . . . 0.03mA to 2mA
Timing Resistor, R
T
. . . . . . . . . . . . . . . . . . . . . 1.8k
to 100k
Timing Capacitor, C
T
. . . . . . . . . . . . . . . . . . . 0.001
F to 0.1F
Operating Ambient Temperature Range
UC1524 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55C to +125C
UC2524 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25C to +85C
UC3524 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0C to +70C
ELECTRICAL CHARACTERISTICS:
Unless otherwise stated, these specifications apply for T
A
= 55C to +125C
for the UC1524, 25C to +85C for the UC2524, and 0C to +70C for the UC3524, V
IN
= 20V, and f = 20kHz,
T
A
= T
J.
PARAMETER
TEST CONDITIONS
UC1524/UC2524
UC3524
UNITS
MIN
MAX
MIN
MAX
Reference Section
Output Voltage
4.8
5.0
5.2
4.6
5.0
5.4
V
Line Regulation
V
IN
= 8 to 40V
10
20
10
30
mV
Load Regulation
I
L
= 0 to 20mA
20
50
20
50
mV
Ripple Rejection
f = 120Hz, T
J
= 25C
66
66
dB
Short Circuit Current Limit
V
REF
= 0, T
J
= 25C
100
100
mA
Temperature Stability
Over Operating Temperature Range
0.3
1
0.3
1
%
Long Term Stability
T
J
= 125C, t = 1000 Hrs.
20
20
mV
Oscillator Section
Maximum Frequency
C
T
= .001mfd, R
T
= 2k
300
300
kHz
Initial Accuracy
R
T
and C
T
Constant
5
5
%
Voltage Stability
V
IN
= 8 to 40V, T
J
= 25C
1
1
%
Temperature Stability
Over Operating Temperature Range
5
5
%
Output Amplitude
Pin 3, T
J
= 25C
3.5
3.5
V
Output Pulse Width
C
T
= .01mfd, T
J
= 25C
0.5
0.5
s
Error Amplifier Section
Input Offset Voltage
V
CM
= 2.5V
0.5
5
2
10
mV
Input Bias Current
V
CM
= 2.5V
2
10
2
10
A
Open Loop Voltage Gain
72
80
60
80
dB
Common Mode Voltage
T
J
= 25C
1.8
3.4
1.8
3.4
V
3
UC1524
UC2524
UC3524
ELECTRICAL CHARACTERISTICS:
Unless otherwise stated, these specifications apply for T
A
= 55C to +125C
for the UC1524, 25C to +85C for the UC2524, and 0C to +70C for the UC3524, V
IN
= 20V, and f = 20kHz,
T
A
= T
J.
PARAMETER
TEST CONDITIONS
UC1524/UC2524
UC3524
UNITS
MIN
MAX
MIN
MAX
Error Amplifier Section (cont.)
Common Mode Rejection Ratio T
J
= 25C
70
70
dB
Small Signal Bandwidth
A
V
= 0dB, T
J
= 25C
3
3
MHz
Output Voltage
T
J
= 25C
0.5
3.8
0.5
3.8
V
Comparator Section
Duty-Cycle
% Each Output On
0
45
0
45
%
Input Threshold
Zero Duty-Cycle
1
1
V
Maximum Duty-Cycle
3.5
3.5
V
Input Bias Current
1
1
A
Current Limiting Section
Sense Voltage
Pin 9 = 2V with Error Amplifier
Set for Maximum Out, T
J
= 25C
190
200
210
180
200
220
mV
Sense Voltage T.C.
0.2
0.2
mV/C
Common Mode Voltage
T
J
= 55C to 85C
for the 1V to 1V Limit
1
+1
1
+1
V
T
J
= 125C
0.3
+1
V
Output Section (Each Output)
Collector-Emitter Voltage
40
40
V
Collector Leakage Current
V
CE
= 40V
0.1
50
0.1
50
A
Saturation Voltage
I
C
= 50mA
1
2
1
2
V
Emitter Output Voltage
V
IN
= 20V
17
18
17
18
V
Rise Time
R
C
= 2k
, T
J
= 25C
0.2
0.2
s
Fall Time
R
C
= 2k
, T
J
= 25C
0.1
0.1
s
Total Standby Current (Note)
V
IN
= 40V
8
10
8
10
mA
The UC1524 is a fixed-frequency pulse-width-modulation
voltage regulator control circuit. The regulator operates at
a frequency that is programmed by one timing resistor
(R
T
), and one timing capacitor (C
T
), R
T
establishes a
constant charging current for C
T
. This results in a linear
voltage ramp at C
T
, which is fed to the comparator provid-
ing linear control of the output pulse width by the error
amplifier. The UC1524 contains an on-board 5V regulator
that serves as a reference as well as powering the
UC1524's internal control circuitry and is also useful in
supplying external support functions. This reference volt-
age is lowered externally by a resistor divider to provide a
reference within the common-mode range of the error
amplifier or an external reference may be used. The
power supply output is sensed by a second resistor di-
vider network to generate a feedback signal to the error
amplifier. The amplifier output voltage is then compared
to the linear voltage ramp at C
T
. The resulting modulated
pulse out of the high-gain comparator is then steered to
the appropriate output pass transistor (Q
1
or Q
2
) by the
pulse-steering flip-flop, which is synchronously toggled by
the oscillator output. The oscillator output pulse also
serves as a blanking pulse to assure both outputs are
never on simultaneously during the transition times. The
width of the blanking pulse is controlled by the valve of
C
T
. The outputs may be applied in a push-pull configura-
tion in which their frequency is half that of the base oscil-
lator, or paralleled for single-ended applications in which
the frequency is equal to that of the oscillator. The output
of the error amplifier shares a common input to the com-
parator with the current limiting and shutdown circuitry
and can be overridden by signals from either of these in-
puts. This common point is also available externally and
may be employed to control the gain of, or to compen-
sate, the error amplifier or to provide additional control to
the regulator.
PRINCIPLES OF OPERATION
4
UC1524
UC2524
UC3524
Output saturation voltage vs load current.
Output dead time vs timing capacitance value.
Open-loop voltage amplification of error amplifier vs
frequency.
TYPICAL CHARACTERISTICS
Oscillator frequency vs timing components.
5
UC1524
UC2524
UC3524
Oscillator
The oscillator controls the frequency of the UC1524 and is
programmed by R
T
and C
T
according to the approximate
formula:
f
R C
T
T
1.18
where
R
T
is in k
where
C
T
is in mF
where
f is in kHz
Practical values of C
T
fall between 0.001mF and 0.1mF.
Practical values of R
T
fall between 1.8k
and 100k.
This results in a frequency range typically from 120Hz to
500kHz.
Blanking
The output pulse of the oscillator is used as a blanking
pulse at the output. This pulse width is controlled by the
value of C
T
. If small values of C
T
are required for fre-
quency control, the oscillator output pulse width may still
be increased by applying a shunt capacitance of up to
100pF from pin 3 to ground. If still greater dead-time is re-
quired, it should be accomplished by limiting the maxi-
mum duty cycle by clamping the output of the error
amplifier. This can easily be done with the circuit in Fig-
ure 1:
Synchronous Operation
When an external clock is desired, a clock pulse of ap-
proximately 3V can be applied directly to the oscillator
output terminal. The impedance to ground at this point is
approximately 2k
. In this configuration R
T
C
T
must be
selected for a clock period slightly greater than that of the
external clock.
If two or more UC1524 regulators are to operated synchro-
nously, all oscillator output terminals should be tied to-
gether, all C
T
terminals connected to single timing capacitor,
and the timing resistor connected to a single R
T
, terminal.
The other R
T
terminals can be left open or shorted to V
REF
.
Minimum lead lengths should be used between the C
T
ter-
minals.
APPLICATION INFORMATION
16
V
REF
COMP
5k
9
GND
8
1N916
Figure 1. Error amplifier clamp.
Figure 2. Single-ended LC switching regulator circuit.
6
UC1524
UC2524
UC3524
Figure 4. Open loop test circuit.
UNITRODE CORPORATION
7 CONTINENTAL BLVD. MERRIMACK, NH 03054
TEL. (603) 424-2410
FAX (603) 424-3460
1
2
15
INV INPUT
NON INV INPUT
16
6
VREF
RT
7
CT
3
OSC OUT
10 SD
12
11
13
14
4
5
9
CA
EA
CB
EB
CLSENSE(+)
CLSENSE(-)
COMP
8
GND
VIN
UC1524
V+
+28 V
5 k
5 k
5 k
2 k
5 k
0.1 F
0.1 F
1 k
1 W
1 k
1 W
100
100
0.1
0.001 F
50 k
500 F
1500 F
+
2N4150
2N4150
20T
20T
5T
5T
5 V
5 A
Figure 3. Push-pull transformer coupled circuit.
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package
Type
Package
Drawing
Pins Package
Qty
Eco Plan
(2)
Lead/Ball Finish
MSL Peak Temp
(3)
UC1524J
OBSOLETE
CDIP
J
16
None
Call TI
Call TI
UC1524J/80937
OBSOLETE
CDIP
J
16
None
Call TI
Call TI
UC1524J883B
OBSOLETE
CDIP
J
16
None
Call TI
Call TI
UC2524DW
ACTIVE
SOIC
DW
16
40
None
CU NIPDAU
Level-2-220C-1 YEAR
UC2524DWTR
ACTIVE
SOIC
DW
16
2000
None
CU NIPDAU
Level-2-220C-1 YEAR
UC2524J
OBSOLETE
CDIP
J
16
None
Call TI
Call TI
UC2524N
ACTIVE
PDIP
N
16
25
None
CU SNPB
Level-NA-NA-NA
UC3524D
ACTIVE
SOIC
D
16
40
None
CU NIPDAU
Level-1-220C-UNLIM
UC3524DTR
ACTIVE
SOIC
D
16
2500
None
CU NIPDAU
Level-1-220C-UNLIM
UC3524DW
ACTIVE
SOIC
DW
16
40
None
CU NIPDAU
Level-2-220C-1 YEAR
UC3524DWTR
ACTIVE
SOIC
DW
16
2000
None
CU NIPDAU
Level-2-220C-1 YEAR
UC3524J
OBSOLETE
CDIP
J
16
None
Call TI
Call TI
UC3524N
ACTIVE
PDIP
N
16
25
None
CU SNPB
Level-NA-NA-NA
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - May not be currently available - please check
http://www.ti.com/productcontent
for the latest availability information and additional
product content details.
None: Not yet available Lead (Pb-Free).
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens,
including bromine (Br) or antimony (Sb) above 0.1% of total product weight.
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
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In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
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PACKAGE OPTION ADDENDUM
www.ti.com
8-Mar-2005
Addendum-Page 1
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