"Linear" goes semi-digital with step-down DC/DC controller merged with digital management

Milpitas, Calif—"Digital power" is a hot topic, and can take two forms: an all-digital control/regulation loop, or a more-conventional analog closed loop but supplemented with digital control of key setpoints and parameters. The LTC3880 falls into the latter camp, providing a dual-output synchronous DC/DC controller combined with digital management via the I²C/PMBus and internal EEPROM.

This allows users to program, change, and monitor power-control performance in real time, using a GUI-based development package which the vendor also provides. Target applications include point-of-load (PoL) converters for high-end, higher-power situations, such as datacom/telecom centers, networking, storage centers, and medical/industrial systems.

The basic controller provides a polyphase (up to six phases can be controlled in conjunction with multiple ICs) step-down control with an input voltage range of 4.5 to 24V and output range of 9.5 to 5.5V, with ±5% output voltage accuracy over the operating temperature range, and the controller includes a differential amplifier to enhance remote output-voltage sensing. Efficiency can be as high as 92% for this IC, which also includes N-channel gate drivers for the user-supplied external MOSFETs.

Using the digital interface, the user can set the output voltage; start-up characteristics including sequencing, tracking, timing delays, and ramp up/ramp down; protection aspects such as under/overvoltage and current limits; actions to be taken when faults occur; margining; and switching frequency.

In the reporting direction, the controller can report input and output voltage and current; faults; historical record; and more. Key set-up and operating data is stored in internal EEPROM, and digital interface is via I²C, PMBus, VID (voltage ID), and other protocols. An internal low dropout regulator (LDO) supports the controller and gate-driver power circuitry; the LTC3880-1 variant allows the user to provide an external bias voltage to improve efficiency.

Pricing, packaging, and availability:  The LTC3880 and LTC3880-1 are available now, and are offered in a thermally enhanced 6 x 6 mm QFN-40 package, in several  temperature ranges, up to -40°C to +125°C. Pricing starts at $5.35 each, in 1000-part lots.

For more information, go to http://www.linear.com/3880.