LM21305

The LM21305 is a full-featured 5A synchronous buck POL regulator optimized for solution size, flexibilty, and high conversion efficiency. High power density LM21305 designs are achieved via monolithic integration of the high-side and low-side power MOSFETs, high switching frequency, current-mode control, and optimized thermal design. The efficiency of the LM21305 is elevated at light loads with diode emulation mode operation and at heavy loads by optimal design of the MOSFET gate drivers to minimize switch dead-times and body-diode conduction losses.

The LM21305 accepts a wide input voltage range of 3V to 18V, facilitating interface to all intermediate bus voltages, including 3.3V, 5V and 12V rails. An output voltage as low as 0.598V is supported with excellent setpoint accuracy and low ripple and RMS noise. The LM21305 offers flexible system configuration with programmable switching frequency from 300 kHz to 1.5 MHz using one resistor or via external clock synchronization. On-chip bias supply sub-regulators alleviate the need for external bias power and simplify PCB layout. The device also offers internal soft-start to limit inrush current, pre-biased and monotonic startup capability, cycle-by-cycle current limiting, and thermal shutdown. Peak current-mode control with a high-gain error amplifier maintains stability throughout the entire input voltage and load current ranges and enables excellent line and load transient response.

Offered in a thermally enhanced LLP-28 package, the LM21305 features internal output over-voltage and over-current protection circuits for increased system reliability. A precision enable pin and integrated input UVLO allow the turn-on of the device to be tightly controlled and sequenced. An integrated open-drain power good indicator provides power rail sequencing capability and fault indication.