harshit suri wrote:
> I need a chip that gives me 4 channels of PWM . I want
> 4 simultaneously
> operating PWM channels. Preferable frequency of
> generation should be greater
> than 50 Khz.
>
> I wish to have at least 8 bits of resolution PER
> channel. meaning 256 levels
> of speed control (The application is DC motor speed
> control)

I'll assume these 4 channels are controlling the same motor and therefore
have the same period.

It sounds like you really want a dsPIC 30F2010.  It includes the new motor
control PWM unit which can drive up to 6 channels with both high and low
side outputs and break before make capability.  This is actually the
smallest of the "motor control" dsPICs, but has plenty of program and data
memory for this job and comes in a 28 pin package.

Now the downside.  This chip isn't available yet.  The first dsPIC in this
family will be the 30F6010 behemoth, with the smaller PICs to follow.  This
might be acceptable depending on when you need to go to volume production.
In the mean time, Microchip is making a 30F2010 lookalike available that is
really a 30F6010 mounted on a board with the 28 pins of the 30F2010 sticking
down in a DIP configuration.  In other words, you can develop with this
adapter plugged into a 28 pin DIP socket, then plug in the real 30F2010 when
it becomes available.

The early dsPICs aren't available to everyone yet.  You will have to talk to
your local Microchip office and try to convince them they should let you in
the early adopters program.  That will probably be easier if you can show a
history with PICs or you can somehow convince them you are blazing the way
into a key market area.

If you can't wait for the 30F2010 you will have to use an 18F PIC in a 40
pin or larger package.


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