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ADC reference voltage

 
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Vitamin-C



Joined: 06 Apr 2004
Posts: 43
Post26 Jul 2004 10:56   ADC reference voltage
HI,

Please see the graph.
It is a ADC inside a IC.

what is the purpose of putting a resistor 4k ohm
instead of biasing the ADC directly.

thx
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petarpav



Joined: 25 Mar 2002
Posts: 557
Helped: 8
Post26 Jul 2004 13:58   ADC reference voltage
Hi. This resistor is used if you want to connect external reference to adc(more precision reference than internal).

Best Regards.
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mazelk



Joined: 23 Apr 2004
Posts: 107
Helped: 2
Location: COLOMBIA
Post26 Jul 2004 17:14   Re: ADC reference voltage
Hi....

This conection seems a bias wire for ADC. I mean, you put a 4k resistance in order to limit the flow current toward ADC. If there is a little flow of current, you may find almost same 2.5 V biasing ADC.
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aNdreiBuuu



Joined: 30 Apr 2001
Posts: 398
Helped: 11
Post26 Jul 2004 17:48   Re: ADC reference voltage
the 4Kohm resistor has 2 reasons:

1. it's the reason described by petarpav.
2. if you use internal ref, the 4Kohm resistor and external cap (common 100nF), make the noise rejection of internal refference. (work as RC integrator)
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nkchenliy



Joined: 11 Feb 2004
Posts: 29
Post27 Jul 2004 0:56   Re: ADC reference voltage
Hi. I think the resistor is connected to external reference voltage. The voltage is used to ADC converting.
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