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UC1525B UC1527B

UC2525B UC2527B

UC3525B UC3527B

DESCRIPTION

The UC1525B/1527B series of pulse width modulator integrated circuits

are designed to offer improved performance and lowered external parts

count when used in designing all types of switching power supplies. The

on-chip +5.1V buried zener reference is trimmed to ±0.75% and the input

common-mode range of the error amplifier includes the reference voltage,

eliminating external resistors. A sync input to the oscillator allows multiple

units to be slaved or a single unit to be synchronized to an external system

clock. A single resistor between the CT and the discharge terminals provide

a wide range of dead time adjustment. These devices also feature built-in

soft-start circuitry with only an external timing capacitor required. A shut

down terminal controls both the soft-start circuitry and the output stages,

providing instantaneous turn off through the PWM latch with pulsed shut

down, as well as soft-start recycle with longer shutdown commands. These

functions are also controlled by an undervoltage lockout which keeps the

outputs off and the soft-start capacitor discharged for sub-normal input volt

ages. This lockout circuitry includes approximately 500mV of hysteresis for

jitter-free operation. Another feature of these PWM circuits is a latch follow-

ing the comparator. Once a PWM pulse has been terminated for any rea-

son, the outputs will remain off for the duration of the period. The latch is

reset with each clock pulse. The output stages are totem-pole designs ca-

pable of sourcing or sinking in excess of 200mA. The UC1525B output

stage features NOR logic, giving a LOW output for an OFF state. The

UC1527B utilizes OR logic which results in a HIGH output level when OFF.

Regulating Pulse Width Modulators

FEATURES

•

8 to 35V Operation

•

5.1V Buried Zener Reference

Trimmed to ±0.75%

•

100Hz to 500kHz Oscillator Range

•

Separate Oscillator Sync Terminal

•

Adjustable Deadtime Control

•

Internal Soft-Start

•

Pulse-by-Pulse Shutdown

•

Input Undervoltage Lockout with

Hysteresis

•

Latching PWM to Prevent Multiple

Pulses

• Dual Source/Sink Output Drivers

• Low Cross Conduction Output Stage

• Tighter Reference Specifications

SLUS376 JULY 1995

BLOCK DIAGRAM

UDG-95055

application

INFO

available

Summary of content (16 pages)

PAGE 1
application INFO available UC1525B UC1527B UC2525B UC2527B UC3525B UC3527B Regulating Pulse Width Modulators FEATURES DESCRIPTION • 8 to 35V Operation The UC1525B/1527B series of pulse width modulator integrated circuits are designed to offer improved performance and lowered external parts count when used in designing all types of switching power supplies. The on-chip +5.1V buried zener reference is trimmed to ±0.
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UC1525B UC1527B UC2525B UC2527B UC3525B UC3527B ABSOLUTE MAXIMUM RATINGS RECOMMENDED OPERATING CONDITIONS (Note 1) Supply Voltage, (+VIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . +40V Collector Supply Voltage (VC). . . . . . . . . . . . . . . . . . . . . . +40V Logic Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V to +5.5V Analog Inputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3V to VIN Output Current, Source or Sink . . . . . . . . . . . . . . . . . .
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UC1525B UC1527B UC2525B UC2527B UC3525B UC3527B ELECTRICAL CHARACTERISTICS:Unless otherwise stated, these specifications apply for TA = –55°C to +125°C for the UC1525B and UC1527B; –40°C to +85°C for the UC2525B and UC2527B; 0°C to +70°C for the UC3525B and UC3527B; +VIN = 20V, TA = TJ. UC1525B/UC2525B UC1527B/UC2527B PARAMETER TEST CONDITIONS MIN TYP MAX ±2 UC3525B UC3527B MIN TYP MAX UNITS ±6 ±2 ±6 % ±0.
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UC1525B UC1527B UC2525B UC2527B UC3525B UC3527B ELECTRICAL CHARACTERISTICS:Unless otherwise stated, these specifications apply for TA = –55°C to +125°C for the UC1525B and UC1527B; –40°C to +85°C for the UC2525B and UC2527B; 0°C to +70°C for the UC3525B and UC3527B; +VIN = 20V, TA = TJ. UC1525B/UC2525B UC1527B/UC2527B PARAMETER TEST CONDITIONS MIN TYP MAX UC3525B UC3527B MIN TYP MAX UNITS Output Drivers (Each Output) (VC = 20V) (cont.
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UC1525B UC1527B UC2525B UC2527B UC3525B UC3527B UDG-95060 UDG-95061 The low source impedance of the output drivers provides rapid charging of power FET input capacitance while minimizing external components. Low power transformers can be driven directly by the UC1525B. Automatic reset occurs during dead time, when both ends of the primary winding are switched to ground.
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UC1525B UC1527B UC2525B UC2527B UC3525B UC3527B Oscillator Charge Time vs. TRand CT Oscillator Discharge Time vs.
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UC1525B UC1527B UC2525B UC2527B UC3525B UC3527B LAB TEST FIXTURE UDG-95067 7
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 25-Sep-2013 TBD: The Pb-Free/Green conversion plan has not been defined. 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.
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PACKAGE MATERIALS INFORMATION www.ti.com 26-Mar-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device UC2525BDWTR Package Package Pins Type Drawing SOIC DW 16 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2000 330.0 16.4 Pack Materials-Page 1 10.75 B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant 10.7 2.7 12.0 16.
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PACKAGE MATERIALS INFORMATION www.ti.com 26-Mar-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) UC2525BDWTR SOIC DW 16 2000 367.0 367.0 38.
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