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DC/DC controller touts precise output sensing

Posted: 25 Jan 2012     Print Version  Bookmark and Share

Keywords:synchronous  step-down  DC/DC  controller 

Linear Technology Corp. rolls a high frequency step-down DC/DC controller that the company says can achieve up to 92 per cent efficiency with a 25A output when operating at 2MHz. The LTC3839 is a controlled on-time single output dual phase synchronous step-down DC/DC controller with operating frequency selectable from 200kHz to 2MHz. It can also be synchronised to an external clock.

Minimum on-time of 30ns enables a high step-down ratio at very high operating frequencies. It features a controlled on-time, valley current-mode architecture and Detect Transient Release to provide fast transient response by increasing operating frequency during a transient event, thus, enabling the output voltage to recover in a few clock cycles. For current applications as high as 250A, up to 12 phases can be paralleled and clocked out of phase.

The LTC3839 operates from 4.5V to 38V input voltage range, targeting a wide range of applications, including most intermediate bus voltages. The device is suitable for point-of-load requirements because on-board N-channel MOSFET gate drivers make it possible to use high power external MOSFETs for output currents up to 50A at output voltages ranging from 0.6V to 5.5V. The controller has a differential amplifier for 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 on-board bias voltage LDO, soft-start or tracking, adjustable current limit, over-voltage protection, current limit foldback and external VCC control.

The controller is specified to account for all error sources including line, load and differential sensing. Its total output voltage accuracy is ±0.25 per cent at 25°C, ±0.67 per cent from 0�C to 85�C, and ±1 per cent 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 Rs.162.24 ($3.18) each.

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