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UC3525B

ACTIVE

Enhanced 35V, Dual 0.4A 400KHz PWM controller with Low output when off, 0C to 70C

Product details

Topology Boost, Buck, Flyback, Forward, Full bridge, Half bridge, Push pull Control mode Voltage Duty cycle (max) (%) 49 Switching frequency (max) (kHz) 500 Features Adjustable switching frequency, Current limiting, Dead time control, Error amplifier, Multi-topology, Soft start, Synchronization pin UVLO thresholds on/off (V) 7/6.5 Operating temperature range (°C) 0 to 70 Rating Catalog Gate drive (typ) (A) 0.4 Vin (max) (V) 40
Topology Boost, Buck, Flyback, Forward, Full bridge, Half bridge, Push pull Control mode Voltage Duty cycle (max) (%) 49 Switching frequency (max) (kHz) 500 Features Adjustable switching frequency, Current limiting, Dead time control, Error amplifier, Multi-topology, Soft start, Synchronization pin UVLO thresholds on/off (V) 7/6.5 Operating temperature range (°C) 0 to 70 Rating Catalog Gate drive (typ) (A) 0.4 Vin (max) (V) 40
PDIP (N) 16 181.42 mm² 19.3 x 9.4 SOIC (DW) 16 106.09 mm² 10.3 x 10.3
  • 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
  • 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

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 shutdown terminal controls both the soft-start circuitry and the output stages, providing instantaneous turn off through the PWM latch with pulsed shutdown, 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 subnormal input voltages. This lockout circuitry includes approximately 500mV of hysteresis for jitter-free operation. Another feature of these PWM circuits is a latch following the comparator. Once a PWM pulse has been terminated for any reason, 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 capable 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.

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 shutdown terminal controls both the soft-start circuitry and the output stages, providing instantaneous turn off through the PWM latch with pulsed shutdown, 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 subnormal input voltages. This lockout circuitry includes approximately 500mV of hysteresis for jitter-free operation. Another feature of these PWM circuits is a latch following the comparator. Once a PWM pulse has been terminated for any reason, 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 capable 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.

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Technical documentation

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Type Title Date
* Data sheet Regulating Pulse Width Modulators datasheet 05 Sep 1999
Selection guide Power Management Guide 2018 (Rev. R) 25 Jun 2018
Application note DN-36 UC1525B/UC1527B Devices - Comparison Summary to UC1525A/27A Devices 05 Sep 1999
Application note DN-62 Switching Power Supply Topology Voltage Mode vs. Current Mode 05 Sep 1999

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PDIP (N) 16 View options
SOIC (DW) 16 View options

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