Vybrid PWM

johnfielden — Sun, 30 Jun 2013 18:56:36 GMT

Hi all, I'm just starting to go through the Vybrid documentation, specifically the VF6. I know it is early, and that the documentation isn't very complete so far. My interest this minute is a PWM generator. I need a PWM to adjust the brightness of several indicator LEDs in my design. The datasheet doesn't mention PWM at all, but it appears that the VF6 uses a timer peripheral similar to those used on Kinetis parts that do claim PWM capability.

I'm using very efficient LEDs such that when all are turned on full brightness the draw is only 300uA. My battery powered device needs long life, and sleeps for long periods of time. So, I need any PWM that I use as little power as possible.

Assuming the VF6 does have PWM capability, here are my questions:

1. How much duty cycle control do I have?

2. Can the low power timer be used to generate PWM?

3. Which of the low power modes allows the PWM to generate (I want my LEDs lit when the design is sleeping).

Thanks,

John

Re: Vybrid PWM

naoumgitnik — Fri, 12 Jul 2013 21:01:05 GMT

Hello John,

As a hardware person, I cannot comment on the PWM specifics, but based on my experience, any processor with a timer does it one way or the other.

At the same time, I can comment on the power consumption optimization for your battery-powered application.

First you have to formulate your power consumption requirements, based on the battery capacity.

Then you have to lower the processor's power consumption by:

using the lowest possible reference clock frequency,
turning all the unnecessary processor's blocks OFF (see power domains for them),
select the Low-Power stop mode suitable for your application,
optimize the power management scheme (linear, based on external NPN transistor),
etc.

Feel free to come with follow-up questions.

Sincerely, Naoum Gitnik.

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