Power Electronics

Synchronous Step-Down DC/DC Controller

Linear Technology Corporation introduces the LTC3839, a high frequency controlled on-time single output dual phase synchronous step-down DC/DC controller that can achieve up to 95% efficiency with a 25A output when operating at 2MHz. The operating frequency is selectable from 200kHz to 2MHz or can be synchronized to an external clock. A low 30ns minimum on-time allows for a high step-down ratio at very high operating frequencies. The controlled on-time, valley current-mode architecture and Detect Transient Release feature provide a very fast transient response by increasing operating frequency during a transient event, enabling the output voltage to recover in only a few clock cycles. Up to 12 phases can be paralleled and clocked out of phase for high current applications (up to 250A).

The LTC3839 operates over a 4.5V to 38V input voltage range, encompassing a wide variety of applications including most intermediate bus voltages. Strong onboard N-channel MOSFET gate drivers allow the use of high power external MOSFETs for output currents up to 50A, at output voltages ranging from 0.6V to 5.5V, making the device ideal for point-of-load requirements. The LTC3839’s differential amplifier provides true remote output voltage sensing of both the positive and negative terminals, enabling high accuracy regulation independent of PCB IR losses (up to ±500mV). The output current is monitored by sensing the voltage drop across the output inductor (DCR) for highest efficiency or by using a sense resistor for extra precision. Additional features include an onboard bias voltage LDO, soft-start or tracking, adjustable current limit, overvoltage protection, current limit foldback and external VCC control.

The LTC3839 offers superior total regulation accuracy and is specified to account for all error sources including line, load and differential sensing. The LTC3839 total output voltage accuracy is +/-0.25% at 25°C, +/-0.67% from 0ºC to 85ºC, and ±1% maximum DC error over the full -40°C to 125°C operating junction temperature range. The LTC3839 is available in a thermally enhanced 5mm x 5mm QFN-32 package. The 1,000-piece price starts at $3.18 each.

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