AVR-Chat

----- Original Message ----- 

From: "Enki" <enkitec@gmail.com>
To: <AVR-Chat@yahoogroups.com>
Sent: Monday, October 27, 2008 1:40 PM
Subject: [AVR-Chat] Inductor at AVCC


> 
> The ATMEGA48 datasheet shows a 10uH inductor connected to AVCC pin 
> for filtering.
> 
> Why 10uH?  Could I use 220uH?

They probably use 10 uH because it works better than anything else.

Leon
--
Leon Heller
Amateur radio call-sign  G1HSM
Yaesu FT-817ND transceiver
Suzuki SV1000S motorcycle
leon355@btinternet.com
http://www.geocities.com/leon_heller

The ATMEGA48 datasheet shows a 10uH inductor connected to AVCC pin 
for filtering.

	Why 10uH?  Could I use 220uH?

	The current at that pin seems to be below 500uA, so a 10Ohm inductor 
(DC resistance) doesn't drop the voltage so much.

	Mark Jordan

--- In AVR-Chat@yahoogroups.com, "Enki" <enkitec@...> wrote:
>The current at that pin seems to be below 500uA, so a 10Ohm
>inductor (DC resistance) doesn't drop the voltage so much.
Keep in mind that the AVcc pin provides all of the source current for 
the digital outputs that are on the same pins as the analog inputs as 
well as for the digital and analog input circuitry.  Although the AVcc 
current in your application might be less than 500uA, it could be much 
higher in general, perhaps several several tens to a 100 milliamps.  
At that level, 100 ohms is quite significant.

Don Kinzer
ZBasic Microcontrollers
http://www.zbasic.net

Considering I'm using the digital outputs to drive MOSFETS
and just two analog inputs, a 10Ohm (TEN OHM) inductor is not a big 
deal. Will do some tests.

	Thanks.
	Mark Jordan

On 27 Oct 2008 at 15:15, Don Kinzer wrote:

> --- In AVR-Chat@yahoogroups.com, "Enki" <enkitec@...> wrote:
> >The current at that pin seems to be below 500uA, so a 10Ohm
> >inductor (DC resistance) doesn't drop the voltage so much.
> Keep in mind that the AVcc pin provides all of the source current
> for 
> the digital outputs that are on the same pins as the analog inputs
> as 
> well as for the digital and analog input circuitry.  Although the
> AVcc 
> current in your application might be less than 500uA, it could be
> much 
> higher in general, perhaps several several tens to a 100 milliamps. 
> At that level, 100 ohms is quite significant.
> 
> Don Kinzer
> ZBasic Microcontrollers
> http://www.zbasic.net
> 
> 
> 
> ------------------------------------
> 
> Yahoo! Groups Links
> 
> 
>

On Mon, Oct 27, 2008 at 11:44 AM, Enki <enkitec@gmail.com> wrote:
>
>        Considering I'm using the digital outputs to drive MOSFETS
> and just two analog inputs, a 10Ohm (TEN OHM) inductor is not a big
> deal. Will do some tests.

Beware.. The static current drain is 0 into the gates, but you still
have to charge the gate capacitance.
You might end up with significant glitches when you switch them on,
especially if they all go at once.
Figure it like a resistive divider, Cin/(Cg1+Cg2....)

Series resistors into the gates will help, if you can deal with the
slowdown in switching.

On 27 Oct 2008 at 11:58, David VanHorn wrote:

> On Mon, Oct 27, 2008 at 11:44 AM, Enki <enkitec@gmail.com> wrote:
> >
> >        Considering I'm using the digital outputs to drive
> MOSFETS
> > and just two analog inputs, a 10Ohm (TEN OHM) inductor is not a
> big
> > deal. Will do some tests.
> 
> Beware.. The static current drain is 0 into the gates, but you
> still
> have to charge the gate capacitance.
> You might end up with significant glitches when you switch them
> on, especially if they all go at once.
> Figure it like a resistive divider, Cin/(Cg1+Cg2....)
> 
> Series resistors into the gates will help, if you can deal with
> the slowdown in switching.


	Yes, I'm aware of that. The gates have 1KOhm in series each one.
	The switching is very slow, just some relays. Besides, the ADC is 
not read during the switching instants.
	I have lots of 220uH 7Ohm inductors that I plan to use.

	Thanks.
	Mark Jordan

Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: "Don Kinzer" <dkinzer@easystreet.net>

Date: Mon, 27 Oct 2008 15:15:01 
To: <AVR-Chat@yahoogroups.com>
Subject: [AVR-Chat] Re: Inductor at AVCC


--- In AVR-Chat@yahoogroups.com, "Enki" <enkitec@...> wrote:
>The current at that pin seems to be below 500uA, so a 10Ohm
>inductor (DC resistance) doesn't drop the voltage so much.
Keep in mind that the AVcc pin provides all of the source current for 
the digital outputs that are on the same pins as the analog inputs as 
well as for the digital and analog input circuitry.  Although the AVcc 
current in your application might be less than 500uA, it could be much 
higher in general, perhaps several several tens to a 100 milliamps.  
At that level, 100 ohms is quite significant.

Don Kinzer
ZBasic Microcontrollers
http://www.zbasic.net





[Non-text portions of this message have been removed]

Hi,
 
	I have an application where using multimaster I2C would help me a
lot, keeping time wasted in communication to a minimum. Searching for
references I mostly have seen people that say that multimaster
implementations using the TWI module is prone to problems, loosing bus
arbitration and data !! It does not make much sense to me, but there is a
bunch of posts about it and the lack of a appnote implementing multimaster
is weird.
 
	Looking at the list archive I found a reference that says that
AVRlib implements multimaster using the TWI module and interrupts. Did
anyone use it sucessfully ? I would need to port it to Codevision and
knowning if it really works before doing the port would be great :-) 
 
	Am I crazy to try to use multiple masters on the same bus that can
also act as slaves ? I have no experience with I2C but the specs says it
should be possible. I will use "packets"  and "CRC's" anyway, so loosing a
few bytes will not kill my application. 
 
Best Regards,
Alexandre Guimaraes