Linear Technology Debuts LTC3700 DC/DC ControllerMay 23, 2002 by Jeff Shepard
Linear Technology Corp. (Milpitas, CA) introduced the LTC3700, a constant-frequency, 550kHz, step-down, dc/dc controller with up to a 94-percent operating efficiency that includes an on-chip, 150mA, low-dropout, linear regulator in a tiny 10-lead MSOP package. The LTC3700 provides a small solution in systems that are powered from one- or two-cell lithium-ion batteries or low-voltage sources where two lower output voltages with low and high current levels are required.
The switching controller's high operating frequency allows use of small inductors for up to 3A of load current, and its constant frequency reduces induced noise while minimizing output filtering. The second output, a low-dropout linear regulator, delivers up to 150mA of output current without requiring an external transistor. For dc/dc conversion accuracy and load protection, the switching controller is current limited and provides ±2.5 percent output-voltage accuracy. The LDO is also current-limited and provides ±3.75 percent output accuracy.
The LTC3700 operates from 2.5V to 9.8V supplies. The output voltage is adjustable to as low as 0.8V. The switching controller section drives an external p-channel MOSFET, which can be turned on continuously in dropout (100-percent duty cycle operation) for longer use of a battery source. The LDO can provide 150mA of output current though its internal p-channel MOSFET pass device, and is protected by both current-limit and thermal shutdown circuits.
Prices start at $2.35 each in 1,000-piece quantities.