Texas Instruments (TI) was showing off their new TMS320F280xx line with its high resolution, 16-channel PWM (HRPWM) module. Each channel can control the edge position with a 150 ps accuracy. This is a neat trick for a 100 MHz TMS320F28044 since it does not generate a faster clock internally to handle the 24-bit PWM support. It is ideal for power control applications such as dc-to-dc converters.
The TMS320F28044 uses the upper 16 bits in a conventional fashion with counter/compare registers. The lower 8 bits are used to delay the pulse edge based on a timing system that is accurate to 150 ps. This approach allows increased edge timing without resorting to a clock that would have to run 256 times faster than it currently does. As with any PWM module, a pair of registers are used to control the low and high times within a cycle. The PWM module can operate in the 24-bit HRPWM mode or using 16-bit PWM timing (see Figure).
Having a large number of channels allows the DSP to control redundant, parallel converters as well as supporting multiple converters generating different voltages. The TMS320F28044 is a 32-bit DSP, so it is quite capable of handling an array of chores while the HRPWM operates in parallel. The processor operates at 100 MHz and has up to 128 kbytes of flash and 20 kbytes of RAM. The chip does have a 12-bit ADC with 16 channels to match the HRPWM.
Pricing for the TMS320F28044 starts under $5. It is available in a 64-pin TQFP. The starter development kit is priced at $495 and includes a copy of C2000 Code Composer Studio. Power factor correction and a dc/dc adapter board are priced at $295.
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