Micropower Voltage Mode PWM
FEATURES • Low 85µA Startup Current
BLOCK DIAGRAM
• Low 300µA Operating Current
• Automa...
Micropower Voltage Mode PWM
FEATURES Low 85µA Startup Current
BLOCK DIAGRAM
Low 300µA Operating Current
Automatically Disabled Startup Pre
regulator
Programmable Minimum Duty Cycle with Cycle Skipping
Programmable Maximum Duty Cycle
Output Current 1A Peak Source and Sink
Programmable Soft Start
Programmable Oscillator Frequency
External Oscillator Synchronization Capability
application INFO available
UCC1581 UCC2581 UCC3581
Note: Pin Connection shown for 14-pin Package
UDG-95011-1
DESCRIPTION
The UCC3581 voltage mode pulse width modulator is designed to control low power isolated DC - DC converters in applications such as Subscriber Line Power (ISDN I.430). Primarily used for single switch forward and flyback converters, the UCC3581 features BiCMOS circuitry for low startup and operating current, while maintaining the ability to drive power MOSFETs at frequencies up to 100kHz. The UCC3581 oscillator allows the flexibility to program both the frequency and the maximum duty cycle with two resistors and a capacitor. A TTL level input is also provided to allow synchronization to an external frequency source.
The UCC3581 includes programmable soft start circuitry, overcurrent detection, a 7.5V linear pre
regulator to control chip VDD during startup, and an on-board 4.0V logic supply.
The UCC3581 provides functions to maximize light load efficiency that are not normally found in PWM controllers.
A linear pre
regulator driver in conjunction with an ext...