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Next-gen DSCs boast flexibility

Posted: 02 Apr 2009 ?? ?Print Version ?Bookmark and Share

Keywords:DSC? controller digital signal? flexibility controllers? power digital?

Emphasizing low cost, small size, low power and flexibility, Microchip Technology Inc. announced the first seven of its next-generation 16bit dsPIC digital signal controllers (DSCs). Microchip aims to increase its share of a digital power market that it believes will grow at a compound annual rate of 40 percent.

The growth of digital loop control, which replaces of analog control with a DSC that controls the power-conversion circuits as well as communications to and from the supply, can be attributed to a range of factors. But the main ones are the lower cost, greater flexibility and efficiency, higher reliability, greater power density, and reduced time-to-market the method affords.

"It also helps protect IP [intellectual property]," said Bill Hutchings, product marketing manager at Microchip. "Before, customers had to use off-the-shelf control-chip solutions that were open to the competition to use, but now they can create IP, secure the flash, and then it becomes difficult to copy that."

Broad adoption
As a result of these advantages, "we've seen a very broad adoption starting around the world," said Hutchings, "and we've had customers reduce parts count by 50 percent or morewith higher power density."

The number of applications is increasing too, going beyond typical power conversion applications such as AC/DC inverters, UPS, AC/DC power supplies and DC/DC converters into lighting applications such as fluorescent and solid-state. This widening range of applications is in part also driving the growth of digital loop control, which, according to Hutchings, will reach 1.4 billion units by 2013 (he was quoting figures from the Darnell Group).

To meet the needs of this market in terms of size, cost and performance, Microchip's new seven-member dsPIC33F GS Series come in 18- to 44-pin packages, have a footprint of 6mm x 6mm, and weigh in at half the cost and twice the processing performance of its previous generation at under $2 in 5K units or more, and 40 MIPS at 3.3V, respectively. The latter is at the extended temperature range of 125C.

Microchip's GS Series comes in a 6mm x 6mm package, costs half as much as the previous generation, has twice the core performance while also adding faster ADCs, a DAC output, tunable oscillator and more memory.

The processor core is fed by one or two ADCs running at 2KSps or 4KSps, again, up to twice the previous generation. Also, "with power conversion you're basically turning off and on the power MOSFETs to get the voltage and current characteristics you need," said Hutchings. "To do that you need a very high-resolution PWM [pulse width modulator]: These are 1ns PWMs."

Also, because a typical design, "would take the ADC input, do a PID loop on it, then go out and modify your PWM output at a fairly high rate of 300 to 500 kHz, you have to be able to do some fairly quick signal processing," said Hutchings. "This is why the signal processor is so critical in the PID loop."

It's also why Microchip made it single-cycle 16 x 16 bit MAC, supplied a 16bit ALU, gave it up to 16 Kbytes of flash and 2 Kbytes of data SRAM to enable fast instruction fetching to ensure fast power conversion. Other, new features, include a relaxation oscillator that's factory tuned, a plethora of comms peripherals, and a DAC output to allow the user to set trip points on external circuitry.

Microchip added the DAC at customers' request, so they can set a trip point for a current-limiting situation, but then take that same voltage and output it so other devices can check that output and adjust theirs to the same level. "So, if you had multiple supplies trying to share a load, you can use that DAC output as a load-sharing device," said Hutchings. Microchip also added peripheral pin slicing so any functionality on any digital pin can be routed to any other digital pin. "This adds flexibility in how our customers lay out their board," said Hutchings.

The GS Series are supported by Microchip's Explorer 16 $129.99 Development Board, MPLAB IDE, MPLAB C Compiler for dsPIC DSCs, MPLAB SIM 30 Software Simulator, MPLAB ICD 3 In-Circuit Debugger and MPLAB Visual Device Initializer. Microchip also announced today the The Buck/Boost Converter PICtail Plus Daughter Board, a power-supply board that consists of two independent DC/DC synchronous buck converters and one independent DC/DC boost converter. All of the necessary power, drive and control signals are presented to board connectors. This board can control two buck stages or one buck and one boost stage, via the demo software running from the onboard dsPIC33 DSC. It costs $89.99.

- Patrick Mannion
DSP DesignLine

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