STR-A6251 ALLEGRO
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Universal-Input/15 W 50 kHz Flyback Switching Regulators Data Sheet 28103.42b STR-A6251 AND STR-A6252 Sanken Power Devices from Allegro MicroSystems Switching Regulators ABSOLUTE MAXIMUM RATINGS at TA = +25°C Control Supply Voltage, VCC . . . . 36 V Drain Switching Current, ID Peak Drain Switching Current, IDM Single-Pulse Avalanche Energy, EAS S/OCP Voltage Range, FB/CC/OLP Voltage Range, FM Voltage Range, Package Power Dissipation, PD MOSFET Channel Temp., TJ . +150°C Storage Temperature Range, * 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. 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 VDSS Derating Required ■Choice of rDS(on) (2.8 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 .
Universal-Input/15 W 50 kHz Flyback Switching Regulators
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 Switching Regulators Copyright © 2005 Allegro MicroSystems, Inc. FUNCTIONAL BLOCK DIAGRAM FEATURES AND BENEFITS (cont’d) ■Automatic Burst Stand-By (intermittent operation) Input Power <0.1 W at No Load ■Auto-Bias Function Stable Burst Operation Without Generating Interference ■Internal Off-Timer Circuit ■Built-In Constant-Voltage/Constant Current ■Multiple Protections: Pulse-by-Pulse Overcurrent Protection (OCP) Overload Protection (OLP) with Auto Restart Latching Overvoltage Protection (OVP) Undervoltage Lockout (UVLO) with Hysteresis Latching Thermal Shutdown (TSD) ■Molded Small-Size 8-Pin Package For Low-Height SMPS This data sheet is based on Sanken data sheet SSE-23297 and SSE-23298.
Universal-Input/15 W 50 kHz Flyback Switching Regulators www.allegromicro.com Switching Regulators ELECTRICAL CHARACTERISTICS at TA = 25°C, VCC = 18 V (unless otherwise specified). Pin Ratings Characteristic No. Symbol Test Conditions Min Typ Max Units Drain-to-Source Breakdown Volt. 8 - 1 V(BR)DSS ID = 300 µA, 650 V V1 – V3 = 0 V (short) Drain Leakage Current IDSS VDS = 650 V, 300 µA V1 – V3 = 0 V (short) On-State Resistance 8 - 1 rDS(on) STR-A6251, ID = 0.4 A 3.95 Ω STR-A6252, ID = 0.4 A 2.8 Ω MOSFET Switching Time 8 - 3 tf 250 ns Operation-Start Voltage 5 - 3 VCC(ON) VCC = 0 t 15.7 V 12.9 14.3 15.7 V Operation-Stop Voltage 5 - 3 VCC(OFF) VCC = 15.7 t 9 V 9.0 V Maximum Switching Frequency 8 - 3 fosc(max) kHz Frequency-Jitter Deviation 8 - 3 Δfosc 3.0 5.0 7.0 kHz Maximum ON Duty Cycle 8 - 3 D max Circuit Current in Operation ICC(ON) 4.0 mA Circuit Current in Non-Operation ICC(OFF) VCC = 12 V µA FM Voltage 2 - 3 VFMH fosc = fosc(max) 4.0 4.5 5.0 V VFML fosc < fosc(max) 3.2 3.6 4.0 V FM Current IFMH -7.7 -11.0 -14.3 µA IFML 7.7 11.0 14.3 µA OCP Threshold Voltage 1 - 3 VOCP 0.67 0.74 0.81 V Leading Edge Blanking Time 8 - 3 tbw 220 320 420 ns Burst Threshold Voltage 4 - 3 Vburst 1.00 1.12 1.24 V OLP Threshold Voltage 4 - 3 VOLP 7.3 8.6 9.9 V Current at OLP Operation IOLP -12 -17 -22 µA OLP Delay Time 4 - 3 tOLP 0.84 1.20 1.56 s Maximum FB Current IFB(MAX) 220 310 400 µA CC Set Voltage 4 - 3 VSET(CC) 4.9 5.8 6.7 V CC Reset Voltage 4 - 3 VRES(CC) VCC = 25 V 3.5 3.9 4.3 V Start-Up Current Istartup VCC = 13 V 0.77 1.10 1.43 mA OVP Operation Voltage 5 - 3 VCC(OVP) VCC = 18 t 35.2 V 28.8 32.0 35.2 V OVP/TSD Latch Sustaining Current ICC(H) VCC =35.2 t 8.6 V 270 µA OVP/TSD Latch Release Voltage 5 - 3 VCC VCC =35.2 t 5.9 V 5.9 7.2 8.6 V Thermal Shutdown TJ 125 140 Thermal Resistance RθJF °C/W Typical values are given for circuit design information only. Negative current is defined as coming out of (sourcing) the specified terminal.
Universal-Input/15 W 50 kHz Flyback Switching Regulators Worcester, Massachusetts 01615-0036 Switching Regulators Avalanche energy is measured at VDD = 99 V, L = 20 mH, IL = 2.5 A. MOSFET TYPICAL CHARACTERISTICS STR-A6252 STR-A6251 Avalanche energy is measured at VDD = 99 V, L = 20 mH, IL = 3.0 A. Recommended Operating Conditions For the availability of parts meeting -40°C requirements, contact Allegro’s Sales Representative.
Universal-Input/15 W 50 kHz Flyback Switching Regulators www.allegromicro.com Switching Regulators MOSFET TYPICAL CHARACTERISTICS (cont’d) STR-A6251 STR-A6252 WARNING — These devices are designed to be operated at lethal voltages and energy levels. Circuit designs that embody these components must conform with applicable safety requirements. Precautions must be taken to prevent accidental contact with power-line potentials. Do not connect grounded test equipment. The use of an isolation transformer is recommended during circuit development and breadboarding.
Universal-Input/15 W 50 kHz Flyback Switching Regulators Worcester, Massachusetts 01615-0036 Switching Regulators Typical Application APPLICATIONS INFORMATION The products described herein are manufactured in Japan by Sanken Electric Co., Ltd. for sale by Allegro MicroSystems, Inc. Sanken and Allegro reserve the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Therefore, the user is cautioned to verify that the information in this publication is current before placing any order. When using the products described herein, the applicability and suitability of such products for the intended purpose shall be reviewed at the users responsibility. Although Sanken undertakes to enhance the quality and reliability of its products, the occurrence of failure and defect of semiconductor products at a certain rate is inevitable. Users of Sanken products are requested to take, at their own risk, preventative measures including safety design of the equipment or systems against any possible injury, death, fires or damages to society due to device failure or malfunction. Sanken products listed in this publication are designed and intended for use as components in general-purpose electronic equipment or apparatus (home appliances, office equipment, telecommunication equipment, measuring equipment, etc.). Their use in any application requiring radiation hardness assurance (e.g., aerospace equipment) is not supported. When considering the use of Sanken products in applications where higher reliability is required (transportation equipment and its control systems or equipment, fire- or burglar-alarm systems, various safety devices, etc.), contact a company sales representative to discuss and obtain written confirmation of your specifications. The use of Sanken products without the written consent of Sanken in applications where extremely high reliability is required (aerospace equipment, nuclear power-control stations, life-support systems, etc.) is strictly prohibited. The information included herein is believed to be accurate and reliable. Application and operation examples described in this publica- tion are given for reference only and Sanken and Allegro assume no responsibility for any infringement of industrial property rights, intellectual property rights, or any other rights of Sanken or Allegro or any third party that may result from its use. Complete product description and applications information is provided in Application Note 28103.40, Series STR- A6200 Flyback Switching Regulators. NOTE: The start-up performance of the IC can only be guaranteed for values of C2 greater than 22 µF. This value is required to keep the internal supply voltage within regulation during IC initialization.
Universal-Input/15 W 50 kHz Flyback Switching Regulators www.allegromicro.com Switching Regulators PACKAGE DIMENSIONS Dimensions in Inches (for reference only) Dimensions in Millimeters (controlling dimensions) Terminal Finish: Pure Sn, 2nd level interconnect category (e3). Product Weight: Approx. 0.51 g. Frame temperature, TF, is measured at the root of pin 3. For more efficient heat radiation, connect a broad PCB pattern at pins 7 and 8. EI 26EI