ADC reference voltage - some questions

[Vitamin-C]

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
Vita

 

[petarpav]

ADC reference voltage

Hi. This resistor is used if you want to connect external reference to adc(more precision reference than internal).

Best Regards.

 

[mazelk]

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.

 

[aNdreiBuuu]

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)

 

[nkchenliy]

Re: ADC reference voltage

Hi. I think the resistor is connected to external reference voltage. The voltage is used to ADC converting.