Re: generation of 16-bit PWM

John B wrote...
>
> joble_5 wrote ...
>
> Does anybody know a chip (not MCU) that generates one or more
> PWM-signals with more than 12-bit resolution and accepts I²C, SPI,
> ... from an MCU.
>
> I can only find 8-bit PWM devices from Philips and National, and
> MCU's with 16-bit PWM. Reprogramming the code for another brand
> of MCU (with 16 bit PWM) is the last option.
>
> Then you'll need to use an MCU. Best bet is Atmel ATmega with
> two 16-bit timers with PWM and two 8-bit timers also with PWM.

Or joble can use triple 16-bit timer/counter ICs like Intel's
82c54 design. These venerable triple timers are wholly-contained
within the VLSI chips used to make all our everyday IBM-compatible
PCs, but IC companies such as Intersil, still manufacture them.
The cp82c54-12 version ($8.99 at DigiKey) can be operated at 12MHz,
which means the 16-bit PWM repetition frequency will be a rather
slow 183Hz. That low PWM frequency explains the relative lack of
enthusiasm for 16-bit PWM designs. In contrast, a 12-bit PWM with
a 12MHz clock cycles at 2.9kHz, and an 8-bit PWM at 47kHz. Another
problem with high-bit-density approaches is the high PWM frequency
necessary to get these very low cycles rates: switching a PWM power
load at a 12MHz rate implies fast sub-50ns switching times, and even
worse, high power-switching repetition rates, which can stress power
circuitry.


--
Thanks,
- Win
.

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