EVALUATION KIT AVAILABLE 3W Primary-Side Transformer MAX256 H-Bridge Driver for Isolated Supplies General Description Benefits and Features The MAX256 is an integrated primary-side controller Simple, Flexible Design Provides Up to 3W to the and H-bridge driver for isolated power-supply circuits. Transformer in Isolated Power Supplies The device contains an on-board oscillator, protection Single Supply +5V or +3.3V Operation circuitry and internal FET drivers to provide up to 3W of Internal Resistor-Programmable Oscillator Mode power to the primary winding of a transformer. The External Clock Mode with Watchdog MAX256 can be operated using the internal program- Disable Mode mable oscillator or can be driven by an external clock Integrated System Protection for improved EMI performance. Regardless of the clock Undervoltage Lockout source being used, an internal flip-flop stage guaran- Thermal Shutdown tees a fixed 50% duty cycle to prevent DC current flow Saves Space on Board in the transformer. 8-Pin Thermally-Enhanced SO Package The MAX256 operates from a single-supply voltage of +5V or +3.3V, and includes undervoltage lockout for controlled startup. The device prevents cross-conduc- tion of the H-bridge MOSFETs by implementing break- Ordering Information before-make switching. Thermal shutdown circuitry PART TEMP RANGE PIN-PACKAGE provides additional protection against damage due to overtemperature conditions. MAX256ASA+ -40 C to +125C 8 SO-EP* The MAX256 is available in the 8-pin thermally-enhanced MAX256ASA/V+T -40 C to +125C 8 SO-EP* SO package. The device is specified for the automotive *EP = Exposed paddle. (-40C to +125C) temperature range. */V denotes an automotive qualified part. +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. Applications Isolated Power Supplies Medical Equipment Industrial Process Telecommunications Control Isolated Communications Links Typical Application Circuit Pin Configuration +5V + 4.7F 470nF +5V ISOLATED 1:2.6CT CK RS 1 8 ST1 ST1 MAX256 0.1F V 2 7 GND CC MODE MAX256 V 3 6 GND CC ST2 CK RS *EP MODE 4 5 ST2 47k GND SO-EP *CONNECT EXPOSED PAD TO GND. +5V TO ISOLATED +5V TYPICAL APPLICATION 19-3748 Rev 2 2/153W Primary-Side Transformer MAX256 H-Bridge Driver for Isolated Supplies Absolute Maximum Ratings (All voltages referenced to GND, unless otherwise noted.) Continuous Power Dissipation (T = +70C) A Supply Voltage V ..................................................-0.3V to +6V 8-Pin SO (derate 18.9mW/C above +70C)..............1509mW CC ST1, ST2, CK RS, MODE (Note 1)................-0.3V to V + 0.3V Operating Temperature Range .........................-40C to +125C CC ST1, ST2 Maximum Continuous Current (T < +125C) ....0.6A Storage Temperature Range .............................-65C to +150C A ST1, ST2 Maximum Continuous Current (T < +100C) ....0.9A Junction Temperature......................................................+150C A ST1, ST2 Maximum Continuous Current (T < +85C) ......1.0A Lead Temperature (soldering, 10s) .................................+300C A Soldering Temperature (reflow) .......................................+260C Note 1: ST1 and ST2 are not protected against short circuits. Damage to the device may result from a short-circuit fault. Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Package Thermal Characteristics (Note 2) SO-EP Junction-to-Ambient Thermal Resistance ( )...............53C/W JA Junction-to-Case Thermal Resistance ( )......................5C/W JC Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial. DC Electrical Characteristics (V = +3.0V to +5.5V, T = T to T . Typical values are at V = +5.0V and T = +25C, unless otherwise noted.) CC A MIN MAX CC A PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Voltage V 3.0 5.5 V CC Supply Current I M OD E = V C K RS un connected ( N ote 3) 1.06 3 mA CC C C , MODE = GND, Disable Supply Current I 50 A SD CK RS unconnected External Resistance Range R 10 k S V = 4.5V (Note 4) 0.5 1.0 CC Driver Total Resistance R OHL V = 3.0V (Note 4) 0.6 1.2 CC Undervoltage Lockout Threshold V V rising 0.8 1.9 2.7 V UVLO CC Undervoltage-Lockout-Threshold V 110 mV UVLO HST Hysteresis V = 4.5V 0.8 Logic-Low Level CC V V IL (MODE, CK RS) V = 3.0V 0.7 CC Logic-High Level V 2.0 V IH (MODE, CK RS) Input Leakage Current I 1A LK (MODE) Internal Pulldown Resistance on R MODE = GND 165 k S INT CK RS Thermal Shutdown T 165 C SHDN Thermal Shutdown Hysteresis T 10 C SHDN HST www.maximintegrated.com Maxim Integrated 2