42V input low-Iq buck controller with advanced spread spectrum for low EMI

The LM25139 is

a 42V, synchronous, buck DC/DC controller with ultra-low IQ for single-output,

high-current regulator circuits. Deriving from a family of

wide-VIN range controllers,

the device uses a peak current-mode control architecture for fast transient response,

convenient loop compensation, and excellent load and line regulation performance.

A high-side switch minimum on time of 25ns

provides large step-down ratios, enabling the direct conversion from 12V and 24V inputs to low-voltage rails for reduced

system design cost and complexity. The LM25139 continues to

operate during input voltage dips as low as 4V, at nearly 100% duty cycle if needed, making

the device an excellent choice for high-performance applications.

The LM25139 comes in a thermally enhanced, 16-pin VQFN package with wettable flank pins and an exposed pad to aid in thermal

dissipation.

Several features

are included to simplify compliance with CISPR 11 or 32

EMI requirements. Adaptively timed, high-current MOSFET gate drivers minimize body diode

conduction during switching transitions, reducing switching losses while also improving

thermal and EMI performance at high input voltage and high switching frequency.

Resistor-adjustable switching frequency as high as 3.2MHz can be synchronized to an external

clock source to eliminate beat frequencies in noise-sensitive applications.

To further

improves the EMI signature, the LM25139 controller has a unique

feature known as dual random spread spectrum (DRSS). Combining

low-frequency triangular and high-frequency random modulations mitigates EMI disturbances

across lower and higher frequency bands, respectively. This hybrid technique aligns with the

multiple resolution bandwidth (RBW) settings specified in industry-standard EMC tests.

Additional

features of the LM25139 include –40°C to 150°C junction

temperature operation, user-selectable PFM mode for lower current consumption at light-load

conditions, open-drain power-good indicator for fault reporting and output monitoring,

precision enable input, monotonic start-up into prebiased load, integrated VCC bias supply

regulator and bootstrap diode, internal 3ms soft-start time, hiccup-mode overload

protection, and thermal shutdown protection with automatic recovery.

The LM25139 controller is qualified to AEC-Q100 grade 1 for

automotive applications. The wide input voltage range, low quiescent current consumption,

high-temperature operation, low minimum on-time, low EMI signature, low component count, and

9mm2 IC size provide an excellent point-of-load regulator choice for

applications requiring enhanced robustness and cost advantages.