Reference Vrh on mc9s12dp256

Started by Florent VERRIERE October 25, 2002
Hello,

About Vrh / Vrl on mc9s12dp256, does it neccessary to use a voltage reference IC for a precise ATD conversion or does power supply voltage is sufficient as evaluation boards seems done?
What is the current of Vrh ?
Is there any internal regulator of Vrh voltage?
Thank you for your answer that conditions my new design. Florent VERRIERE
J. SAURON S.A. / Micro Plus



I try to use ratiometric designs for my A/D sources. In that manner the
precise value of the reference is not critical. In a current design, for
example, Vrh is connected to Vcc via a PolySwitch fuse (to prevent circuit
damage of someone shorts the external Vrh line) and Vrl is connected to
analogue ground. I then use precision potentiometers (which by definition
are ratiometric devices) and in one case I have been able to find a pressure
transducer with a 0.5V to 4.5V ratiometric output.

Good luck, Bob Smith

--- Avoid computer viruses, Practice safe hex ---

-- Specializing in small, cost effective
embedded control systems -- Robert L. (Bob) Smith
Smith Machine Works, Inc.
9900 Lumlay Road
Richmond, VA 23236 804/745-1065
----- Original Message -----
From: "Florent VERRIERE" <>
To: <>
Sent: Friday, October 25, 2002 4:46 AM
Subject: [68HC12] Reference Vrh on mc9s12dp256 > Hello,
>
> About Vrh / Vrl on mc9s12dp256, does it neccessary to use a voltage
reference IC for a precise ATD conversion or does power supply voltage is
sufficient as evaluation boards seems done?
> What is the current of Vrh ?
> Is there any internal regulator of Vrh voltage?
> Thank you for your answer that conditions my new design. > Florent VERRIERE
> J. SAURON S.A. / Micro Plus >
>
> -------------------- >
> ">http://docs.yahoo.com/info/terms/ >




Robert smith,
I understand but my question is about Vcc is more dependant of temperature
and some other tolerance like resistor,..

A voltage reference assure the system to have a certain precision depending
of the component you choice .

Florent. ----- Original Message -----
From: "Robert Smith" <>
To: <>
Sent: Friday, October 25, 2002 1:54 PM
Subject: Re: [68HC12] Reference Vrh on mc9s12dp256 > I try to use ratiometric designs for my A/D sources. In that manner the
> precise value of the reference is not critical. In a current design, for
> example, Vrh is connected to Vcc via a PolySwitch fuse (to prevent circuit
> damage of someone shorts the external Vrh line) and Vrl is connected to
> analogue ground. I then use precision potentiometers (which by definition
> are ratiometric devices) and in one case I have been able to find a
pressure
> transducer with a 0.5V to 4.5V ratiometric output.
>
> Good luck, Bob Smith
>
> --- Avoid computer viruses, Practice safe hex ---
>
> -- Specializing in small, cost effective
> embedded control systems -- > Robert L. (Bob) Smith
> Smith Machine Works, Inc.
> 9900 Lumlay Road
> Richmond, VA 23236 804/745-1065 >
> ----- Original Message -----
> From: "Florent VERRIERE" <>
> To: <>
> Sent: Friday, October 25, 2002 4:46 AM
> Subject: [68HC12] Reference Vrh on mc9s12dp256 > > Hello,
> >
> > About Vrh / Vrl on mc9s12dp256, does it neccessary to use a voltage
> reference IC for a precise ATD conversion or does power supply voltage is
> sufficient as evaluation boards seems done?
> > What is the current of Vrh ?
> > Is there any internal regulator of Vrh voltage?
> > Thank you for your answer that conditions my new design.
> >
> >
> > Florent VERRIERE
> > J. SAURON S.A. / Micro Plus
> >
> >
> >
> >
> >
> >
> >
> > --------------------
> >
> >
> >
> > ">http://docs.yahoo.com/info/terms/
> >
> >
> >
> -------------------- >
> ">http://docs.yahoo.com/info/terms/ >