The LM5045 PWM controller contains all of the features necessary to implement full-bridge topology power converters 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 100 V. This highly integrated controller-driver provides dual 2-A high-side and low-side gate drivers for the four external bridge MOSFETs plus control signals for the secondary-side synchronous rectifier MOSFETs. External resistors program the leading and trailing edge dead-time between the main and synchronous rectifier control signals. Intelligent start-up of the synchronous rectifiers allows monotonic turnon of the power converter even with prebias load conditions. Additional features include cycle-by-cycle current limiting, hiccup mode restart, programmable soft-start, synchronous rectifier soft-start, and a 2-MHz capable oscillator with synchronization capability and thermal shutdown. • Highest Integration Controller for Small Form Factor, High-Density Power Converters • High-Voltage Start-Up Regulator • Intelligent Sync Rectifier Start-Up Allows Linear Turnon Into Prebiased Loads • Synchronous Rectifiers Disabled in UVLO mode and Hiccup Mode • Two Independent, Programmable Synchronous Rectifier Dead-Time Adjustments • Four High-Current 2-A Bridge Gate Drivers • Wide-Bandwidth Optocoupler Interface • Configurable for Either Current Mode or Voltage Mode Control • Dual-Mode Overcurrent Protection • Resistor Programmed 2-MHz Oscillator • Programmable Line UVLO and OVP. The A4957 is a full-bridge controller for use with external N-channel power MOSFETs and is specifically designed for applications with high-power inductive loads such as brush DC motors. A unique charge pump regulator provides full ( >10 V ) gate drive for battery voltages down to 7 V and allows the A4957 to operate with a reduced gate drive, down to 4.5 V. A bootstrap capacitor is used to provide the above battery supply voltage required for N-channel MOSFETs. A unique bootstrap charge management system ensures that the bootstrap capacitor is always sufficiently charged to supply the high-side gate drive circuit. Each of the power MOSFETs is controlled independently but all are protected from shoot-through by dead time that is userconfigured by an external resistor. Integrated diagnostics provide indication of undervoltage and overtemperature faults. The A4957 is supplied in a 24-contact 4 mm × 4 mm × 0.75 mm QFN with an exposed pad for enhanced thermal dissipation. It is lead (Pb) free, with 100% matte tin leadframe plating (suffix –T). The A3921 is a full-bridge controller for use with external N-channel power MOSFETs and is specifically designed for automotive applications with high-power inductive loads, such as brush DC motors. The HIP2101 is a high frequency, 100V Half Bridge N-Channel power MOSFET driver IC. It is equivalent to the HIP2100 with the added advantage of full TTL/CMOS compatible logic input pins.
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March 2019
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