STRA6252 - Universal Input/15 W 50 kHz Flyback Switching Reg

The STR-A6251 and STR-A6252 are 50 kHz PWM topology (with
±5% frequency jittering for minimum EMI) regulators specifically
designed to satisfy the requirements for increased integration and
reliability in flyback converters. They incorporate a primary control and
drive circuit with avalanche-rated power MOSFETs. The STR-A6252
features higher allowable switching current and lower on-resistance.
The STR-A6251 is also available for 67 kHz operation.
Covering the power range from below 21 watts or 24 watts for a
230 VAC input, or to 15 or 20 watts for a universal (85 to 264 VAC)
input, these devices can be used in a wide range of applications, from
DVD players and VCR player/recorders to ac adapters for cellular
phones and digital cameras. An auto-burst standby function reduces
power consumption at light load, while multiple protections, including
the avalanche-energy guaranteed MOSFET, provide high reliability of
system design.
Cycle-by-cycle current limiting, undervoltage lockout with hyster-
esis, overvoltage protection, and thermal shutdown protect the power
supply during the normal overload and fault conditions. Overvoltage
protection and thermal shutdown are latched after a short delay. The
latch may be reset by cycling the input supply. Low start-up current and
a low-power standby mode selected from the secondary circuit completes
a comprehensive suite of features. Both devices are provided in an 8-pin
mini-DIP plastic package with pin 6 removed.

FEATURES AND BENEFITS

50 kHz PWM with ±5% Frequency Jittering Cost Reduction of EMI Noise Filtering
Rugged 650 V Avalanche-Rated MOSFET Simplified Surge Absorption
No V DSS Derating Required
Choice of rDS(on)
Auto-Burst Mode for Stand-By Operation or Light Loads
Less Transformer Audible Noise
Built-In Leading Edge Blanking
Soft Start and Low Start-Up Current
Start-Up Circuit Disabled in Operation
Low Operating Current (4 mA max)