Universal-Input/15 W 50 kHz

Flyback Switching Regulators

STR-A6252

Sanken Power Devices

from Allegro MicroSystems

Switching

Regulators

ABSOLUTE MAXIMUM RATINGS

STR-A6251 . . . . . . . . . . . . . . 2.5 A*

STR-A6252 . . . . . . . . . . . . . . 3.0 A*

STR-A6251 . . . . . . . . . . . . . . . 2.5 A

STR-A6252 . . . . . . . . . . . . . . . 3.0 A

STR-A6251 . . . . . . . . . . . . . . 72 mJ

STR-A6252 . . . . . . . . . . . . . 123 mJ

S/OCP Voltage Range,

FB/CC/OLP Voltage Range,

FM Voltage Range,

total . . . . . . . . . . . . . . . . . . . . 1.5 W

Storage Temperature Range,

-40°C to +125°C

* Drain switching current is limited by tem-

perature (page 2) and safe operating area

(page 4).

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.

■ 50 kHz PWM with ±5% Frequency Jittering

Cost Reduction of EMI Noise Filtering

■ Rugged 650 V Avalanche-Rated MOSFET

Simplified Surge Absorption

■ Choice of

Ω or 3.95 Ω maximum)

■ 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)

continued

Always order by complete part number, e.g., STR-A6251 .