The LM25145
42-V synchronous buck
controller is designed to regulate from a high input voltage source or from an input rail subject
to high voltage transients, minimizing the need for external surge suppression components. A
high-side switch minimum on-time of 40 ns facilitates large step-down ratios, enabling the direct
step-down conversion from a 24
V nominal input to low-voltage rails for reduced system complexity and solution cost. The
LM25145 continues to
operate during input voltage dips as low as 6 V, at nearly 100% duty cycle if needed, making it
well suited for high-performance industrial control, robotic, datacom, and RF power amplifier
applications.Forced-PWM (FPWM) operation eliminates frequency variation to minimize EMI, while a
user-selectable diode emulation feature lowers current consumption at light-load conditions.
Cycle-by-cycle overcurrent protection is accomplished by measuring the voltage drop across the
low-side MOSFET or by using an optional current sense resistor. The adjustable switching frequency
as high as 1 MHz can be synchronized to an external clock source to eliminate beat frequencies in
noise-sensitive applications. The LM25145
voltage-mode controller drives external high-side and low-side N-channel power switches with robust
7.5-V gate drivers suitable for standard-threshold MOSFETs. Adaptively-timed gate drivers with
2.3-A source and 3.5-A sink capability minimize body diode conduction during switching transitions,
reducing switching losses and improving thermal performance when driving MOSFETs at high input
voltage and high frequency. The LM25145 can be powered from the output of the switching regulator or
another available source, further improving efficiency.A 180° out-of-phase clock output relative to the internal oscillator at SYNCOUT is ideal
for cascaded or multi-channel power supplies to reduce input capacitor ripple current and EMI
filter size. Additional features of the LM25145 include a configurable soft-start, an open-drain Power Good monitor
for fault reporting and output monitoring, monotonic start-up into prebiased loads, integrated VCC
bias supply regulator and bootstrap diode, external power supply tracking, precision enable input
with hysteresis for adjustable line undervoltage lockout (UVLO), hiccup-mode overload protection,
and thermal shutdown protection with automatic recovery.The LM25145
controller is offered in a 3.5-mm × 4.5-mm thermally-enhanced, 20-pin VQFN package with additional
spacing for high-voltage pins and wettable flanks for optical inspection of solder joint
fillets.
