LM5046January 17, 2012Phase-Shifted Full-Bridge PWM Controller with Integrated MOSFET DriversGeneral DescriptionThe LM5046 PWM controller contains all of the features nec- essary to implement a Phase-Shifted Full-Bridge topology power converter using either current mode or voltage mode control. This device is intended to operate on the primary side of an isolated dc-dc converter with input voltage up to 100V. This highly integrated controller-driver provides dual 2A high and low side gate drivers for the four external bridge MOS- FETs, plus control signals for the secondary side syn- chronous rectifier MOSFETs. External resistors program the dead-time to enable zero-volt switching of the primary FETs. Intelligent startup of the synchronous rectifiers allows mono- tonic turn-on of the power converter even with pre-bias load conditions. Additional features include cycle-by-cycle current limiting, hiccup mode restart, programmable soft-start, syn- chronous rectifier soft-start and a 2 MHz capable oscillator with synchronization capability and thermal shutdown.FeaturesHighest Integration Controller for Small Form Factor, High Density Power Converters High Voltage Start-up Regulator Intelligent Sync Rectifier Start-up Allows Linear Turn-on into Pre-biased Loads Synchronous Rectifiers Disabled in UVLO mode and Hiccup Mode Two Independent, Programmable Dead-Time Adjustments to Enable Zero-Volt Switching. Four High Current 2A Bridge Gate Drivers Wide-Bandwidth Opto-coupler Interface Configurable for either Current Mode or Voltage Mode Control Dual-mode Over-Current Protection Resistor Programmed 2MHz Oscillator Programmable Line UVLO and OVP PackageseTSSOP-28 LLP-28 (5mm x 5mm)Simplified Phase-Shifted Full-Bridge Power Converter30147801 2012 Texas Instruments Incorporated301478 SNVS703Fwww.ti.comLM5046 Phase-Shifted Full-Bridge PWM Controller with Integrated MOSFET DriversConnection DiagramsTop View30147802 TSSOP28www.ti.com2LM5046Top View30147803 LLP-28 PackageOrdering InformationOrder NumberPackage TypeNSC Package DrawingSupplied AsLM5046MHeTSSOP-28MXA28ARail of 48 UnitsLM5046MHXeTSSOP-28MXA28ATape and Reel of 2500 UnitsLM5046SQLLP-28SQA28ATape and Reel of 1000 UnitsLM5046SQXLLP-28SQA28ATape and Reel of 4500 Units3www.ti.comLM5046Pin DescriptionsTSSOP PinLLP PinNameDescriptionApplication Information125UVLOLine Under-Voltage LockoutAn external voltage divider from the power source sets the shutdown and standby comparator levels. When UVLO reaches the 0.4V threshold the VCC and REF regulators are enabled. At the 1.25V threshold, the SS pin is released and the controller enters the active mode. Hysteresis is set by an internal current sink that pulls 20A from the external resistor divider.226OVP/OTPOver Voltage ProtectionAn external voltage divider from the input power supply sets the shutdown level during an over-voltage condition. Alternatively, an external NTC thermistor voltage divider can be used to set the shutdown temperature. The threshold is 1.25V. Hysteresis is set by an internal current that sources 20 A of current into the external resistor divider.327RAMPInput to PWM ComparatorModulation ramp for the PWM comparator. This ramp can be a signal representative of the primary current (current mode) or proportional to the input voltage (feed-forward voltage mode). This pin is reset to GND at the end of every cycle.428CSCurrent Sense InputIf CS exceeds 750mV the PWM output pulse will be terminated, entering cycle-by-cycle current limit. An internal switch holds CS low for 40nS after either output switches high to blank leading edge transients.51SLOPESlope Compensation CurrentA ramping current source from 0 to 100A is provided for slope compensation in current mode control. This pin can be connected through an appropriate resistor to the CS pin to provide slope compensation. If slope compensation is not required, SLOPE must be tied to ground.62COMPInput to the Pulse Width Modulator An external opto-coupler connected to the COMP pin sources current into an internal NPN current mirror. The PWM duty cycle is at maximum with zero input current, while 1mA reduces the duty cycle to zero. The current mirror improves the frequency response by reducing the AC voltage across the opto-coupler.73REFOutput of a 5V referenceMaximum output current is 15mA. Locally decouple with a 0.1F capacitor.84RT/SYNCOscillator Frequency Control and Frequency SynchronizationThe resistance connected between RT and AGND sets the oscillator frequency. Synchronization is achieved by AC coupling a pulse to the RT/SYNC pin that raises the voltage at least 1.5V above the 2V nominal bias level.95AGNDAnalog GroundConnect directly to the Power Ground.106RD1Passive to Active DelayThe resistance connected between RD1 and AGND sets the delay from the falling edge of HO1/SR1 or LO1/SR2 and the rising edge of LO1 or HO1 respectively.117RD2Active to Passive DelayThe resistance connected between RD2 and AGND sets the delay from the fallin