1.5A, 15V synchronous boost regulator with output disconnect

August 24, 2015 // By Graham Prophet
LTC3121 is a 3 MHz current mode, synchronous boost DC/DC converter with integrated output disconnect. It achieves 95% efficiency, and occupies a 3 x 4 mm DFN package.

The device’s internal 1.5A switches deliver output voltages as high as 15V from an input voltage range of 1.8V at start-up (0.5V when running) to 5.5V, for battery or standard 3.3V and 5V power sources. The LTC3121 delivers up to 400 mA of continuous output current at 12V from a 5V input. Its 1.5A current limit suits it for input current-constrained applications such as PCI Express while minimising the size of the required externals. Pin-selectable Burst Mode operation lowers quiescent current to 25 µA, providing extended battery run time. The combination of its thermally enhanced 3 x 4 mm DFN-12 package and a constant switching frequency of up to 3 MHz enables the designer to balance PCB solution size with required efficiency.

The LTC3121 has internal synchronous switches with an RDS(ON) of 121 mΩ (N-channel) and 188 mΩ (P-channel) to deliver efficiencies as high as 95%. Output disconnect allows the output voltage to be completely discharged in shutdown and also eliminates large inrush currents during start-up, minimising stress on the input supply. The LTC3121 also regulates the output voltage when the input voltage exceeds the output voltage, making the device compatible with any battery chemistry. For applications demanding the lowest possible noise operation, the LTC3121 can be set via an external pin to operate in constant PWM mode. Additional features include external synchronisation, output overvoltage protection and robust short-circuit protection.

Pricing starts at $2.33 (1000). An industrial-grade version, the LTC3121IDE, is guaranteed to operate over the -40°C to 125°C operating junction temperature range and is priced at $2.73 (1,000).

Linear Technology; www.linear.com/product/LTC3121

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