Synchronous step-down regulator features input and output current limiting and current monitoring

July 20, 2012 // Paul Buckley

Linear Technology has introduced a high efficiency, 3 MHz synchronous buck regulator that offers both input and output current limiting and monitoring.

The LTC3626 incorporates a constant frequency/controlled on-time, current-mode architecture that delivers up to 2.5 A of continuous output current at output voltages as low as 0.6V from a 3 mm x 4 mm QFN package.

The device's current-mode operation offers excellent line and load transient response even with high step-down ratios. The LTC3626 operates from an input voltage range of 3.6 V to 20 V, making it suitable for a wide range of applications, including dual/multiple-cell Li-Ion battery stacks and 5 V to 18 V intermediate bus systems. Its average input current and output current limiting are pin-programmable, making it well suited for applications such as USB power. The LTC3626’s switching frequency is user programmable and synchronizable from 500 kHz to 3 MHz, enabling the use oflow cost capacitors and inductors.

The LTC3626 uses internal switches with RDS(ON) of 11 5mOhms and 70 mOhms to deliver efficiencies as high as 95%. Its unique control architecture enables it to achieve duty cycles as low as 5%, while maintaining switching frequencies up to 2.25 MHz, making it ideal for high step-down ratio applications, such as 12 VIN to 1.2 VOUT conversions. Burst Mode operation is used to maximize light load efficiency, requiring only 300 µA (at no load), important for applications demanding maximum battery run time.

For applications requiring the lowest possible noise, the LTC3626 can be configured to run in forced continuous mode, for minimum noise and potential RF interference. Furthermore, an internal die temperature monitor provides a voltage proportional to temperature which can be programmed to limit maximum die temperatures.

Additional features include a power good voltage monitor, output voltage tracking capability and short circuit protection.

Availability and Pricing

The LTC3626EUDC is available in a 3 mm x 4 mm QFN-20. Pricing starts at $3.45 each in 1,000-piece quantities. An industrial grade version, the LTC3626IUDC offers guaranteed performance over the -40 to 125°C operating junction temperature range, priced at $3.97 each in 1,000-piece quantities. Both versions are available from stock.

More information about the LTC3626 synchronous buck regulator visit www.linear.com/product/LTC3626

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