UNITRODE UC1524, UC2524, UC3524 Technical data

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Advanced Regulating Pulse Width Modulators

UC1524 UC2524 UC3524

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

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 -55°C to +125°C. The UC2524 and UC3524 are designed for operation from -25°C to +85°C and 0° to +70°C, respectively.

BLOCK DIAGRAM

(RAMP)

INV INPUT

NI INPUT

GROUND

(SUBSTRATE)

REFERENCE REGULATOR

+5V

REF

OSC

OSC OUT

COMPARATOR

10k

+5V TO ALL

INTERNAL

CIRCUITRY

+5V

–SENSE

+SENSE

+5V 12

SHUTDOWN

COMPENSATION

SLUS180D - NOVEMBER 1999 - REVISED AUGUST 2002

ABSOLUTE MAXIMUM RATINGS (Note 1)

Supply Voltage, VCC(Notes 2 and 3) . . . . . . . . . . . . . . . . . 40V

Collector Output Current. . . . . . . . . . . . . . . . . . . . . . . . . 100mA

Reference Output Current . . . . . . . . . . . . . . . . . . . . . . . . 50mA

Current Through C Power Dissipation at T Power Dissipation at T

Terminal . . . . . . . . . . . . . . . . . . . . . . –5mA

= +25°C (Note 4). . . . . . . . . . 1000mW

= +25°C (Note 4). . . . . . . . . . 2000mW

Operating Junction Temperature Range . . . . –55°C to +150°C

Storage Temperature Range . . . . . . . . . . . . . –65°C to +150°C

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

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, VCC. . . . . . . . . . . . . . . . . . . . . . . . . . 8V to 40V

Reference Output Current . . . . . . . . . . . . . . . . . . . . . 0 to 20mA

Current through C Timing Resistor, R Timing Capacitor, C Operating Ambient Temperature Range

UC1524 . . . . . . . . . . . . . . . . . . . . . . . . . . . . –55°C to +125°C

UC2524 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –25°C to +85°C

UC3524 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0°C to +70°C

Terminal . . . . . . . . . . . . . –0.03mA to –2mA

. . . . . . . . . . . . . . . . . . . . . 1.8kΩ to 100kΩ

. . . . . . . . . . . . . . . . . . . 0.001µF to 0.1µF

CONNECTION DIAGRAM

INV INPUT

NON INV

INPUT

OSC OUT

CLSENSE(+)

CLSENSE (–-)

GND

UC1524 UC2524 UC3524

OSC

REF

REG

S/D

REF

S/D

COMP

ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for T

for the UC1524, –25°C to +85°C for the UC2524, and 0°C to +70°C for the UC3524, V T

A=TJ

= 20V, and f = 20kHz,

= –55°C to +125°C

UC1524/UC2524 UC3524 UNITS

PARAMETER TEST CONDITIONS

MIN MAX MIN MAX

Reference Section

Output Voltage 4.8 5.0 5.2 4.6 5.0 5.4 V Line Regulation V Load Regulation I Ripple Rejection f = 120Hz, T Short Circuit Current Limit V

IN = 8 to 40V 10 20 10 30 mV

L = 0 to 20mA 20 50 20 50 mV

J = 25°C 66 66 dB

REF = 0, TJ = 25°C 100 100 mA

Temperature Stability Over Operating Temperature Range 0.3 1 0.3 1 % Long Term Stability T

J = 125°C, t = 1000 Hrs. 20 20 mV

Oscillator Section

Maximum Frequency C Initial Accuracy R Voltage Stability V

= .001mfd, RT= 2kΩ 300 300 kHz

and CTConstant 5 5 %

= 8 to 40V, TJ= 25°C 1 1 %

Temperature Stability Over Operating Temperature Range 5 5 % Output Amplitude Pin 3, T Output Pulse Width C

= 25°C 3.5 3.5 V

= .01mfd, TJ= 25°C 0.5 0.5

Error Amplifier Section

Input Offset Voltage V Input Bias Current V

= 2.5V 0.5 5 2 10 mV

= 2.5V 2 10 2 10

Open Loop Voltage Gain 72 80 60 80 dB Common Mode Voltage T

= 25°C 1.8 3.4 1.8 3.4 V

µs

µA

UC1524 UC2524 UC3524

ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for T

for the UC1524, –25°C to +85°C for the UC2524, and 0°C to +70°C for the UC3524, V T

A=TJ

PARAMETER TEST CONDITIONS

Error Amplifier Section (cont.)

Common Mode Rejection Ratio T Small Signal Bandwidth A Output Voltage T

Comparator Section

Duty-Cycle % Each Output On 0 45 0 45 % Input Threshold Zero Duty-Cycle 1 1 V

Input Bias Current 1 1

Current Limiting Section

Sense Voltage Pin 9 = 2V with Error Amplifier

Sense Voltage T.C. 0.2 0.2 mV/°C Common Mode Voltage T

Output Section (Each Output)

Collector-Emitter Voltage 40 40 V Collector Leakage Current V Saturation Voltage I Emitter Output Voltage V Rise Time R Fall Time R

Total Standby Current (Note)

= 25°C 70 70 dB

V = 0dB, T

= 25°C 0.5 3.8 0.5 3.8 V

Maximum Duty-Cycle 3.5 3.5 V

Set for Maximum Out, T

= –55°C to 85°C

for the –1V to 1V Limit

= 125°C –0.3 +1 V

= 40V 0.1 50 0.1 50

C = 50mA 1 2 1 2 V

= 20V 17 18 17 18 V

C = 2kΩ,T C = 2kΩ,T

= 40V 8 10 8 10 mA

= 25°C 3 3 MHz

= 25°C

= 25°C 0.2 0.2

= 25°C 0.1 0.1

UC1524/UC2524 UC3524 UNITS

MIN MAX MIN MAX

190 200 210 180 200 220 mV

–1 +1 –1 +1 V

= 20V, and f = 20kHz,

= –55°C to +125°C

µA

µs µs

PRINCIPLES OF OPERATION

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

), and one timing capacitor (CT), RTestablishes a

constant charging current for C voltage ramp at C

, 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 pulse out of the high-gain comparator is then steered to

. This results in a linear

. The resulting modulated

the appropriate output pass transistor (Q

1 or Q2)bythe

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

. 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.

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