AVR-Chat

any suggested DC-DC converter? i prefer from texas intruments or maxim. they're the only company i can ask for samples. it should be five volts output.
 
thanks for the help.
 
-jay

erikc <firewevr@airmail.net> wrote:

----- Original Message -----
From: "jay marante" <jaythesis@yahoo.com>
To: <AVR-chat@yahoogroups.com>
Sent: Tuesday, April 06, 2004 11:58
Subject: [AVR-Chat] current in MCU and thte sleep mode at
mega16 issue


> just to clear things up...
>
> the datasheet of ATMEGA16L says that DC current Vcc and
GND pins = 200mA. <-- what does this mean?

This means that the total amount of current that is allowed
to enter or leave these pins must not be greater than 200mA.
The part by itself uses very little current, but when you
attach it to things, those things also draw current.
Individually, a small amount, but collectively it can add
up.

> also, what does Icc in power supply current at 8MHz = 20mA
(max) mean?

Current suck on a CMOS part is proportional to its operating
frequency.  In this case, if you clock it at 8 MHz, the part
will draw (nominally) 20 mA.  If you run it at 4 MHz, that
current drops to somewhere around 10 mA.  If you stop it
altogether, it will draw very little current.

> is 200mA means that it is its maximum current that should
be supplied to the MCU?
> and, does 20mA mean that is its normal power consumption?

Yes and yes.

> im using a max883 linear regulator. it is labeled as: 5V,
low-dropout, low-Iq, 200mA Linear regulator.
>    -- Low 220mV dropout voltage at 200mA output current
>    -- 11uA Quiescent current
>
> is this enough to power my system when the input to the
regulator is a 9V alkaline battery? the only device
connected to the MCU is a 4x20 LCD and a 4x3 keypad. i
really need the battery to last long.

If your regulator is adequately heatsinked, then yes it will
work.  But if you want the battery to last long, use a
switching regulator.

> any suggestions? should i change the linear regulator with
a DC-DC converter?

Yes.

> thanks for the help.
>
> -jay

Do you absolutely have to use a 9 volt battery?  (I am
assuming it is the square kind with snaps on the end).  If
not, consider running your project from "AA" or "C" cells.

Erikc  - firewevr@airmail.net
///
"An Fhirinne in aghaidh an tSaoil."
"The Truth against the World."
        -- Bardic Motto



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