I spent the afternoon on the exposition floor at APEC to see what is going in digital power. In particular, I was looking for general purpose technology that would help in building isolated digital controlled switch mode power supplies. In particular, I was interested in technology to roll your own controller. Maxim showed a state controlled offering, but unless you have $$$ in your hand, high volume in your pocket, and a gold pen to sign an NDA, all you could do was see a couple of waveforms and come back in Q3 to get a data sheet.
The platforms that were on display were:
- TI's Piccolo Real Time CPU
- Microchip's dsPIC
- Microsemi's SmartFusion
- Cypress' PSoC 5
Piccolo is a 32 bit real time microcontroller with a 150ps resolution PWM, 12 ADC, comparators, I2C, Flash, control law accelerator, floating point, complex math, etc. Pricing is about $3. dsPIC is a 16 bin digital signal controller with 10/12 bit ADC, DACs, I2C, PWM, Flash, MAC, etc. Pricing is similar to Piccolo.
Both of these offerings are basically a microcontroller with support for digital control applications. Microchip ran one of the educational sessions and pointed out that a CPU designed for digital control had to have optimized IO and timer system to minimize delay from the sample and hold to ADC, through the compensator to the PWM. The pipeline is about 4uS. It seemed clear that with this delay, feedforward mechanisms are pretty normal. They also touted their flexible PWM that could be configured in many different ways. I have not looked at Piccolo's PWM architecture, but this would be something to look at in addition to the total delay. Both the Piccolo and dsPIC have pre-canned libraries that can do PID or similar analog control techniques digitally, but one can go pure digital.
SmartFusion has an ARM microcontroller, an programmable analog with ADC, DAC, current monitors, temp monitors, comparators, and FPGA. The guy doing booth duty said that customers like it because they can roll their own PWM in the FPGA and play other tricks to differentiate their end products. The drawback is if you don't want to make your own PWM, your a bit stuck. (Note that you will not find these on the Microsemi site, you have to use the Actel site. You would think that a key word search on the Microsemi site would find SmartFusion, but no...) Microsemi indicated that there are a dozen or so new designs using SmartFusion, which released 9-12 months ago, so this is new stuff. Pricing is $40-$50. Perhaps that is why there are so few customers. However, given the price of FPGAs, this price makes some sense, just don't use it in a low cost SMPS.
The PSoC5 is a general purpose PSoC, but there is also a PowerPSoC, the PowerPSoC has PWMs and a Hysteretic controller. The block diagram does not show any CPU. Looks like a building block system for simple stuff like LED lighting applications. The PSoC5 has a PWM and some digital blocks. The basic blocks seem to support digital control. Pricing on the PSoC5 is not available yet, or at least I could not find any prices, and the datasheet is marked preliminary. Development kits seem to be for sale on the Cypress website. Older PSoC prices are in $5 range. I'll guess these are in the $10+ range.
It was quite clear who was tuned in when it came to digital control. It was clearly Microchip. They taught a digital control seminar. They were totally excited about dsPIC applications and had real advice about design tradeoffs and performance. TI was promoting a broad offering and not focused specifically on digital control. Microsemi did not have anyone in the booth that deeply understood it. Cypress was asleep at the wheel. (Maxim was peeing their paths over their new chip, but no details or datasheet. Just a "trust me, this is so cool", all though it might be a one trick pony.)
My take, without a deep dive into these device's capabilities, is that Microchip and TI are probably the most worth looking into as SPMS controllers. Microsemi's offering is quite new, there are not very many customers, so it will be hard to leverage any experience outside Actel. Cypress is a wild card, but if they are not engaged at APEC, it is hard to take them serious.
One could also use an FPGA with MAC, such as the Spartan 3e, but that is probably much more work, and they are not cheap. I'm betting the dsPIC would be fun to play with and will probably buy a starter kit and play around.