Synchronous step-down DC/DC controller supports wide operating junction temperatures

July 14, 2011 // By Paul Buckley
Linear Technology Corporation has introduced the H- and MP- grade versions of the company’s LTC3851A, a wide input voltage range (4 V to 38 V) synchronous step-down DC/DC controller that encompasses a broad range of applications, including most intermediate bus voltages and battery chemistries. The onboard MOSFET gate drivers enable the use of high power external MOSFETs to produce output currents up to 25 A with output voltages ranging from 0.8 V to 5.5 V, ideal for point-of-load requirements.

The H- and MP-grade versions are tested and guaranteed to operating junction temperature ranges from -40 to 150°C and -55 to 150°C, respectively. Applications include automotive systems, industrial, medical, datacom and telecom.

A constant-frequency, current-mode architecture allows a selectable fixed or phase-locked loop (PLL) frequency from 250 kHz to 750 kHz. Output current sensing is accomplished by measuring the voltage drop across the output inductor (DCR) or using an optional sense resistor. Current foldback limits MOSFET heat dissipation during short circuit and overload conditions. Selectable continuous, pulse skipping or Burst Mode operation is user controlled to optimize light load efficiency. With up to 99% duty cycle, the LTC3851A/-1 has a low dropout voltage, a useful feature for extending run times in battery powered applications.

Additional features include tracking and adjustable soft-start. The LTC3851A-1 differs from the LTC3851A in that it has a power good signal instead of adjustable current limit.

The LTC3851AH/-1 and LTC3851AMP/-1 are available in a thermally enhanced MSOP-16 package. The 1000-piece price starts at $2.24 each for the H-grade devices and $5.29 each for the MP-grade parts, respectively.

More information the LTC3851AH/-1 and LTC3851AMP/-1 synchronous step-down DC/DC controllers at