Buck Pulse Width Modulator Stepdown Voltage Regulator

UC3578 is not recommended for new designs
Although this product continues to be in production to support previous designs, we don't recommend it for new designs. Consider one of these alternates:
open-in-new Compare alternates
Same functionality with different pin-out to the compared device
LM5145 ACTIVE 75V Synchronous Buck Controller With Wide Input Voltage and Duty Cycle Ranges Voltage mode controller with adjustable switching frequency
Similar functionality to the compared device
TPSM365R3 ACTIVE 3-V to 65-V input, 1-V to 13-V output, 0.3-A synchronous buck converter power module Save board space, simplify design and speed time to market with an integrated-inductor power module.

Product details

Vin (min) (V) 11 Vin (max) (V) 72 Iout (max) (A) 0.2 Operating temperature range (°C) 0 to 70 Control mode Voltage mode Rating Catalog Vout (min) (V) 5 Vout (max) (V) 62 Iq (typ) (A) 0.01 Duty cycle (max) (%) 100
Vin (min) (V) 11 Vin (max) (V) 72 Iout (max) (A) 0.2 Operating temperature range (°C) 0 to 70 Control mode Voltage mode Rating Catalog Vout (min) (V) 5 Vout (max) (V) 62 Iq (typ) (A) 0.01 Duty cycle (max) (%) 100
SOIC (D) 16 59.4 mm² 9.9 x 6
  • Provides Simple Single Inductor Buck PWM Step-Down Voltage Regulation
  • Drives External High Side NMOS Switch
  • 14V to 72V Input Voltage Operating Range
  • Contains 100kHz Internal Oscillator, 2V Reference and UVLO
  • Soft Start on Power Up
  • Overcurrent Shutdown Followed by Soft Start
  • Provides Simple Single Inductor Buck PWM Step-Down Voltage Regulation
  • Drives External High Side NMOS Switch
  • 14V to 72V Input Voltage Operating Range
  • Contains 100kHz Internal Oscillator, 2V Reference and UVLO
  • Soft Start on Power Up
  • Overcurrent Shutdown Followed by Soft Start

The UC3578 is a PWM controller with an integrated high side floating gate driver. It is used in buck step down converters and regulates a positive output voltage. Intended to be used in a distributed power system, the IC allows operation from 14V to 72V input voltage which range includes the prevalent telecomm bus voltages. The output duty cycle of the UC3578 can vary between 0% and 90% for operation over the wide input voltage and load conditions.

The UC3578 simplifies the design of the single switch PWM buck converter by incorporating a floating high side driver for an external N-channel MOSFET switch. It also features a 100kHz fixed frequency oscillator, an internal 2V precision reference, an error amplifier configured for voltage mode operation, and a PWM comparator with latching logic. Complementing the traditional voltage mode control block, the UC3578 incorporates an overcurrent shutdown circuit with full cycle soft re-start to limit the input current to a user defined maximum value during overload operation. Additional functions include an under voltage lockout circuit to insure that sufficient input supply voltage is present before any switching activity can occur.

The UC2578 and the UC3578 are both available in surface mount and thru-hole power packages.

The UC3578 is a PWM controller with an integrated high side floating gate driver. It is used in buck step down converters and regulates a positive output voltage. Intended to be used in a distributed power system, the IC allows operation from 14V to 72V input voltage which range includes the prevalent telecomm bus voltages. The output duty cycle of the UC3578 can vary between 0% and 90% for operation over the wide input voltage and load conditions.

The UC3578 simplifies the design of the single switch PWM buck converter by incorporating a floating high side driver for an external N-channel MOSFET switch. It also features a 100kHz fixed frequency oscillator, an internal 2V precision reference, an error amplifier configured for voltage mode operation, and a PWM comparator with latching logic. Complementing the traditional voltage mode control block, the UC3578 incorporates an overcurrent shutdown circuit with full cycle soft re-start to limit the input current to a user defined maximum value during overload operation. Additional functions include an under voltage lockout circuit to insure that sufficient input supply voltage is present before any switching activity can occur.

The UC2578 and the UC3578 are both available in surface mount and thru-hole power packages.

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* Data sheet Buck Pulse Width Modulator Stepdown Voltage Regulator datasheet 05 Sep 1999
User guide UC3578 Telecom Buck Converter Reference Design 16 Oct 2001

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