reference voltage in Pipelined ADC

[Yun Lin]

If the reference voltage is generated in ADC, not come from outside, it seems it's difficulty to get more than 10bit resolution even the bandgap circuit designed in.
For example, 1v referenc voltage is generated, but because process and matching reason, the referenc may be 1.004v. So the 10bit can't be sured especially when the input voltage is 0v or 1v.
How can we do for this problem. Or this porblem is not big problem when we design the system.
Thanks for your reply.

 

[elbadry]

What you should care about is the variaion with temperature at a given process corner. This is typically in ppm ( better than 10 bit accuracy ).

 

[Yun Lin]

Yes. You are right. But the absolute value will be changed. If may cause problem when the analog signal is at +/- vref because it will give out wrong digital number

 

[Vamsi Mocherla]

Hey in case of ADCs and their respective references, please verify whether the process supports trimming. If that is the case, you can get your resistors trimmed to get the accurate bandgap value. You can hence do the design to get the value in vicinity and after trim, you can get the most accurate value.

Another thing, if the value increases, there should not be no problem because, your Vin is still inside your VREF limits. The problem comes if your Vin is outside your VREF limit.

 

[maxwellequ]

Deviations on the reference voltage cause a gain error in the transfer function of the ADC. This is usually not a problem, since a certain ADC will always have the same reference voltage(*).
Note that systems are usually made in order not that have the signals to be digitized near the full scale of the ADC.

Regards.

(*)-apart from the variations caused by changing the temperature, as stated by e elbadry