Thursday, July 30, 2009

Linear Unveils LTC3546 Dual-Channel Regulator

Linear Technology has introduced a dual-channel synchronous buck regulator that can deliver either dual 2A outputs or 3A from one channel and 1A from the other, with up to 96 per cent efficiency. Using a constant-frequency, current-mode architecture, the LTC3546 operates from an input-voltage range of 2.25V to 5V, making it suitable for single-cell Li-ion/polymer or multi-cell alkaline/NiCad/NiMH applications.

Each output is adjustable from 0.6V to 5V and has turn-on supply tracking. Separate Run and Power Good PINs enable independent control of each channel. The LTC3546's switching frequency can be set at 2.25MHz or is programmable from 750kHz to 4MHz, enabling the designer to optimise efficiency while avoiding critical noise-sensitive frequency bands. The combination of its 4mm x 5mm QFN-28 package and its high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint.

The LTC3546's design consists of 2A and 1A primary synchronous switches and a 1A dependent synchronous output switch, which can be externally connected to either of the primary outputs to produce either 3A and 1A outputs or dual 2A outputs. The 2A primary switch can be run either in phase with the additional switches or 180 degrees out of phase via an external phase pin. The LT3546's Burst Mode operation minimises quiescent current to 160uA (both channels on) in no-load conditions. The current threshold at which Burst Mode operation begins can be independently programmed for each channel, optimising overall efficiency.

For applications demanding very low noise, the LTC3546 can also be run in pulse skipping or forced continuous modes to minimise output ripple. The LTC3546 offers a Power Good indicator and is synchronisable to an external clock. Other features include an external synchronisation capability and over-temperature and short-circuit protection. The LTC3546EUFD is available in a 4mm x 5mm QFN-28 and is priced at USD3.75 (GBP2.28) each in 1,000-piece quantities. The industrial-grade version - LTC3546IUFD - is tested and guaranteed to operate from a -40C to +125C operating junction temperature and is priced at USD4.41 in 1,000-piece quantities. All versions are available from stock.

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