I have some questions about the 10uF decoupling cap:
1. Is it required if I am not planning on using the ADC?
2. What voltage rating should I use? (6.3v good enough?)
3. Must it be Tantalum?
I could not find any guidelines in the MSP manuals.
Thanks

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1. Required? NO. Necessary? Most likely.
2. How much safety factor do you want above your power supply voltage
(which you did not mention)? 6.3V is 100% over a power supply voltage
of 3.15V.
3. No.

Emmett Redd Ph.D. mailto:E...@missouristate.edu
Professor (417)836-5221
Department of Physics, Astronomy, and Materials Science
Missouri State University Fax (417)836-6226
901 SOUTH NATIONAL Dept (417)836-5131
SPRINGFIELD, MO 65897 USA

"In theory there is no difference between theory and practice. In
practice there is." -- Yogi Berra or Jan van de Snepscheut

> -----Original Message-----
> From: m... [mailto:m...]
> On Behalf Of merapcb
> Sent: Tuesday, May 12, 2009 11:22 AM
> To: m...
> Subject: [msp430] Decoupling cap?
> I have some questions about the 10uF decoupling cap:
> 1. Is it required if I am not planning on using the ADC?
> 2. What voltage rating should I use? (6.3v good enough?)
> 3. Must it be Tantalum?
> I could not find any guidelines in the MSP manuals.
> Thanks
> Start a New Thread

----- Original Message -----
From: "merapcb"
To:
Sent: Tuesday, May 12, 2009 5:22 PM
Subject: [msp430] Decoupling cap?
>
> I have some questions about the 10uF decoupling cap:
> 1. Is it required if I am not planning on using the ADC?
> 2. What voltage rating should I use? (6.3v good enough?)
> 3. Must it be Tantalum?
> I could not find any guidelines in the MSP manuals.

I always use one. I use a 10 uF ceramic, they are cheaper and smaller than
tantalum and electrolytic parts.

Leon

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This is a loaded question. It all depends on how tolerant your system is. If you're blinking a LED from a battery, you probably need very little (if any!) decoupling. If you're drawing huge amounts of current in bursts while needing precise ADC outputs and DAC measurements, you probably need a pretty elaborate filtering scheme.

You can always build a prototype and put a scope on the various power-supply lines. If it's too noisy, add some capacitance.

I know there are some talented analog guys who read this, so maybe if you told us some more about your application, you may get some good tips.

Stuart

--- In m..., "merapcb" wrote:
> I have some questions about the 10uF decoupling cap:
> 1. Is it required if I am not planning on using the ADC?
> 2. What voltage rating should I use? (6.3v good enough?)
> 3. Must it be Tantalum?
> I could not find any guidelines in the MSP manuals.
> Thanks
>

Start a New Thread

Hi,
First, you should give a lot more information than you are giving. You say "about the 10uF", assuming we all know what your hardware is, at what pdf you're looking and whay that 10uF is connected to. I don't remember any pin that requires a 10uF.

As I remember, a tantalum 10uF plus a ceramic 0.1uF connected to and near the VeRef pin is recommended if using an external voltage reference for ADC12, or the same caps are required to be connected and near VRef if you use the internal voltage reference generator to stabilize it and operate within specifications, which is either 2.5V or 1.5V.
The internal reference generator of ADC10 does not need these capacitors.

All this is covered in the MSP430 user guides.

Michael K.
--- In m..., "merapcb" wrote:
> I have some questions about the 10uF decoupling cap:
> 1. Is it required if I am not planning on using the ADC?
> 2. What voltage rating should I use? (6.3v good enough?)
> 3. Must it be Tantalum?
> I could not find any guidelines in the MSP manuals.
> Thanks
>

Start a New Thread