LTC3901 Secondary Side Synchronous Driver for Push-Pull and Full-Bridge Converters FEATURES DESCRIPTIO N-Channel Synchronous MOSFET Driver The LTC 3901 is a secondary side synchronous rectifier Programmable Timeout driver designed to be used in isolated push-pull and full- Reverse Inductor Current Sense bridge converter power supplies. The chip drives two Gate Drive Transformer Synchronization external N-channel MOSFETs and accepts a transformer- Sequence Monitor generated bipolar input to maintain sychronization with Wide V Supply Range: 4.5V to 11V the primary side controller. CC 15ns Rise/Fall Times at V = 5V, C = 4700pF CC L The LTC3901 provides a full range of protection features Undervoltage Lockout for the external MOSFETs. A programmable timeout func- Small 16-Lead SSOP Package tion is included that disables both drivers when the syn- U chronization signal is missing or incorrect. Additionally, APPLICATIO S the chip senses the output inductor current through the 48V Input Isolated DC/DC Converters drain-source resistance of the two MOSFETs, turning off Isolated Telecom Power Supplies the MOSFETs if the inductor current reverses. The LTC3901 Distributed Power Step-Down Converters also shuts off the drivers if the supply is low or if the Industrial Control System Power Supplies synchronization sequence is incorrect. Automotive and Heavy Equipment , LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIO L1 V ISOLATION OUT + 12V BARRIER C OUT T1 V IN 36V TO 72V + CSE V CC MA MB ME ME CSE GND LTC3901 DRVA DRVB + CSF PV CC LTC3723 PUSH-PULL MF MF CONTROLLER CSF PGND COMP V SDRA SDRB FB SYNC TIMER T2 OUT FB LT4430 OR LT1431 OPTOCOUPLER DRIVER COMP 3901 F01 Figure 1. Simplified Isolated Push-Pull Converter 3901f 1 U ULTC3901 UUW ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO (Note 1) TOP VIEW ORDER PART Supply Voltage PV 1 16 V CC CC NUMBER V , PV ............................................................................ 12V CC CC ME 2 15 MF Input Voltage ME 3 14 MF LTC3901EGN CSE , CSF , TIMER ................. 0.3V to (V + 0.3V) CC PGND 4 13 PGND SYNC ...................................................... 12V to 12V CSE 5 12 CSF + + Input Current CSE 6 11 CSF GN PART + + CSE , CSF ..................................................................... 15mA TIMER 7 10 GND MARKING 8 GND 9 SYNC Operating Temperature Range (Note 2) ...40C to 85C 3901 Storage Temperature Range ..................65C to 150C GN PACKAGE 16-LEAD NARROW PLASTIC SSOP Lead Temperature (Soldering, 10 sec).................. 300C T = 125C, = 130C/W JMAX JA Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes specifications which apply over the full operating temperature range. V = 5V, T = 25C unless otherwise specified. (Note 3) CC A SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS V Supply Voltage Range 4.5 5 11 V CC V V Undervoltage Lockout Threshold Rising Edge 4.1 4.5 V UVLO CC V Undervoltage Lockout Hysteresis Rising Edge to Falling Edge 0.5 V CC I V Supply Current V = 0V 0.5 1 mA VCC CC SYNC f = 100kHz, C = C = 4700pF (Note 4) 715 mA SYNC ME MF Timer V Timer Threshold Voltage 10% V /5 10% V TMR CC I Timer Input Current V = 0V 6 10 A TMR TMR t Timer Discharge Time C = 1000pF, R = 4.7k 40 120 ns TMRDIS TMR TMR V Timer Pin Clamp Voltage C = 1000pF, R = 4.7k 2.5 V TMRMAX TMR TMR Current Sense (Note 5) + I+CS Input Current V + = 0V 1 A CS CS ICS Input Current V = 0V 1 A CS CS + V CS Pin Clamp Voltage I = 5mA, Driver Off 11 V CSMAX IN V Current Sense Threshold Voltage V = 0V 7.5 10.5 13.5 mV CS CS (Note 6) 318mV SYNC Input I SYNC Input Current V = 10V 1 10 A SYNC SYNC V SYNC Input Positive Threshold 1.0 1.4 1.8 V SYNCP SYNC Positive Input Hysteresis (Note 7) 0.2 V V SYNC Input Negative Threshold 1.8 1.4 1.0 V SYNCN SYNC Negative Input Hysteresis (Note 7) 0.2 V Driver Output R Driver Pull-Up Resistance I = 100mA 0.9 1.2 ONH OUT 1.6 R Driver Pull-Down Resistance I = 100mA 0.8 1.2 ONL OUT 1.6 I Driver Peak Output Current (Note 7) 2 A PK 3901f 2 U WWW