The LM27403 is a feature-rich, easy-to-use, synchronous buck controller offering
exceptional levels of integration and performance for superior efficiency in high power density,
point-of-load (POL) DC-DC regulator solutions. The resistor-programmable switching frequency from
200 kHz to 1.2 MHz and integrated, high-current MOSFET gate drivers with adaptive deadtime offer
flexibility to optimize solution size and maximize conversion efficiency.
High precision and low output voltage are easily obtained with a 0.6-V, 1% accurate
voltage reference together with a 30-ns high-side MOSFET minimum controllable on-time. Using
lossless inductor dc resistance (DCR) current sensing and an inexpensive 2N3904 BJT to sense
temperature remotely at the inductor, the LM27403 supports accurate and thermally compensated
overcurrent protection (OCP).
The LM27403 has a conventional voltage-mode control loop with high gain-bandwidth error
amplifier and PWM input voltage feedforward to simplify compensation design and enable excellent
transient response throughout the full line voltage and load current ranges. Forced-PWM (FPWM)
operation eliminates frequency variation to minimize EMI in sensitive applications. An open-drain
Power Good circuit provides power-rail sequencing and fault reporting. Other features include
programmable system-level thermal shutdown with automatic recovery, output voltage remote sense,
configurable soft-start, monotonic start-up into prebiased loads, an integrated bias supply
low-dropout (LDO) regulator, external power supply tracking, precision enable with customizable
hysteresis for programmable line undervoltage lockout (UVLO), and synchronization capability for
beat frequency sensitive and multiregulator applications. The LM27403 is offered in a 4-mm x 4-mm
thermally enhanced WQFN-24 package with 0.5-mm pitch.