Prev: Problem with simple OpAmp Circuit, need help
Next: Hey Tim, a unity gain 12 to 330 V DC converter :-)
From: john1987 on 14 Jul 2010 13:08
Hi,

Thanks. I did not understand the following part about restricting the
PWM to 1% duty cycle increments. Does it mean that I can not do for
example 50% duty cycle

This means that with a 50MHz processor and a
500kHz PWM you'll be restricted to 1% duty cycle increments.

John
From: linnix on 14 Jul 2010 13:20
On Jul 14, 10:08 am, john1987 <conphil...(a)hotmail.com> wrote:
> Hi,
>
> Thanks. I did not understand the following part about restricting the
> PWM to 1% duty cycle increments. Does it mean that I can not do for
> example 50% duty cycle
>

That means, for example, with 7 bits (1/128), you can do exactly

49.21875%
50.00000%
50.78125%

but nothing in between.
From: john1987 on 14 Jul 2010 13:21
Hi,

in the light of what we have disscuseed so far, the following micro
C8051F411's PWM section can generate PWM of 3 MHz. The PWM has 8 bit
of resolution and master clock is 24MHz. Am I right?

http://www.keil.com/dd/docs/datashts/silabs/c8051f41x.pdf



Thanks

John

From: Tim Wescott on 14 Jul 2010 13:23
On 07/14/2010 10:08 AM, john1987 wrote:
> Hi,
>
> Thanks. I did not understand the following part about restricting the
> PWM to 1% duty cycle increments. Does it mean that I can not do for
> example 50% duty cycle
>
> This means that with a 50MHz processor and a
> 500kHz PWM you'll be restricted to 1% duty cycle increments.

If you have a 50MHz clock then (in the absence of fancy circuitry)
everything will happen in 20ns increments. So with a 500kHz PWM cycle,
you will indeed be able to get 50% duty cycle (1us on and 1us off), or
51% duty cycle (1.02us on and 9.8us off), but the 1% _increment_ is the
smallest you'll be able to get -- you won't, for instance, be able to
get to 50.2% from 50%.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html
From: German on 14 Jul 2010 13:43
On 14.07.2010 19:21, john1987 wrote:
> Hi,
>
> in the light of what we have disscuseed so far, the following micro
> C8051F411's PWM section can generate PWM of 3 MHz. The PWM has 8 bit
> of resolution and master clock is 24MHz. Am I right?
>
> http://www.keil.com/dd/docs/datashts/silabs/c8051f41x.pdf
>

No, the maximum frequency with 8bit resolution is 24MHz / 256 = 93.75 kHz
First  |  Prev  |  Next  |  Last
Pages: 1 2 3 4 5
Prev: Problem with simple OpAmp Circuit, need help
Next: Hey Tim, a unity gain 12 to 330 V DC converter :-)