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DC/DC controller optimises channel current sharing

Posted: 14 Mar 2011     Print Version  Bookmark and Share

Keywords:DC/DC controller  current balance  current-mode control 

Linear Technology Corp. debuts the LTC3869/-2, a dual-output synchronous step-down DC/DC controller that optimises current sharing between channels when paralleled. Its 4V to 38V input aims for a wide variety of applications, including most intermediate bus voltages and battery chemistries as also ASIC and FPGA supplies, power distribution, network servers and automotive power systems.

The controller's low 2mV sense voltage maximum mismatch allows it to maintain better than ±4 per cent current mismatch between channels during steady state and transient conditions when both outputs are paralleled.

The 1.1Ω on-board gate drivers minimise switching losses and allow the use of high power external MOSFETs to produce output currents up to 25A per channel with output voltages ranging from 0.6V to 12.5V.

This device claims to maintain superior jitter-free performance even when the switching edges cross between phases, ideal for noise sensitive requirements.

The LTC3869/-2's current-mode control and minimum on-time of just 90ns also target high frequency, high step-down ratio applications requiring a small solution size.

Tracking and sequencing functions optimise power-up and power-down of multiple power rails. This device operates with all N-channel MOSFETs and produces ±1 per cent accurate output voltages over a wide -40°C to 125°C operating junction temperature range.

The output current is sensed by monitoring the voltage drop across the output inductor (DCR) for highest efficiency or by using a sense resistor.

A fixed operating frequency can be programmed from 250kHz to 780kHz or can be synchronised to an external clock with its internal phase-locked loop (PLL). Additional features include an on-board LDO for IC power, programmable soft start, a power good signal and external VCC control.

The LTC3869 is pin compatible to the LTC3850 in both package options. The LTC3869 is available in a 4mm x 5mm QFN package and the LTC3869-2 is offered in an SSOP-28. The 1000-piece price starts at Rs.120.52 ($2.65) each.





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