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DC/DC controller enables digital programming

Posted: 28 Aug 2012     Print Version  Bookmark and Share

Keywords:synchronous  step-down  DC/DC  controller  digital power system 

Linear Technology Corp. rolls the LTC3883/-1 synchronous step-down DC/DC controller. The device features an I2C-based PMBus interface for digital power system management.

It offers a current-mode switching regulator and mixed signal data acquisition. Supported by the LTpowerPlay software development system via an easy-to-use GUI, it enables digital programming and read back for real-time control and monitoring of critical point-of-load converter functions.

Programmable control parameters offered by the device include output voltage, margining and current limits, input and output supervisory limits, switching frequency and tracking. It can capture and store regulator configuration settings and telemetry variables using on-chip data converters and EEPROM. These include input voltage and current, output voltage and current, duty cycle, temperature and fault logging.

With the configurations stored on-chip, the controller can power-up autonomously without burdening the host processor. Default settings can be optionally configured by external resistor dividers for output voltage, switching frequency, phase and device address. Multiple designs can be easily calibrated and configured in firmware to optimise a single hardware design for a range of applications.

The LTC3883 can be configured for up to six phases that can be interleaved and paralleled for accurate sharing among multiple ICs, minimising input and output filtering requirements for high current and/or multiple output requirements. Applications include high current ASIC, FPGA and processor supplies in telecom, datacom, computing and storage markets.

Driving power MOSFETs
The controller has high current integrated gate drivers to drive N-channel power MOSFETs from input voltages ranging from 4.5V to 24V. It is said to produce ±0.50 per cent accurate output voltages from 0.5V to 5.5V with output currents up to 30A per phase over the full operating temperature range. An integrated amplifier provides true differential remote output voltage sensing, enabling high accuracy regulation, independent of board IR voltage drops. Highest efficiency is achieved by sensing current using the voltage drop across the output inductor (DCR), or an external sense resistor can be optionally used. Programmable DCR temperature compensation maintains an accurate and constant current limit over a broad temperature range. The device's minimum on-time of just 90nsec makes the LTC3883/-1 suited for compact high frequency/high step-down ratio applications, said the company. Accurate timing across multiple chips and event-based or time-based sequencing allow the optimisation of power-up and power-down of complex, multiple rail systems.

Other features are storage of identification and traceability data, cycle-by-cycle current limit, adjustable soft start, a synchronisable switching frequency, and programmable GPIO pins to indicate part status and to provide autonomous recovery from faults.

The LTC3883 features an on-board LDO for controller and gate drive power, and the LTC3883-1 allows for an external bias voltage for highest efficiency. Both parts are available in a thermally enhanced 5mm x 5mm QFN-32 package. The extended temperature range grade is specified over -40°C to 105°C, while the industrial grade part is specified over a -40°C to 125°C operating junction temperature range.

Priced starting at Rs.263.39 ($4.82) each in 1,000-piece quantities, both devices are available from stock.

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