How to get 12-bit SAR ADC without self-calibration using CMOS process?

[uladz55]

Hi,
who knows, is it possible to get 12 bit SAR ADC without self-calibration using modern CMOS process?
Sampling rate is less then 100 kHz.

 

[yeewong_su]

sar adc calculation

This will be ok!

Maybe the samp rate can be 500K ~ 1M

 

[uladz55]

sar adc

Hi,

do you know any commercial 12 bit SAR ADC without selfcalibration?

Thanks

 

[layes2]

sar adc 12bits

yes
guy
is there any thing that on sell?
high the samping rate perhaps helpful.

 

[uladz55]

Re: 12-bit SAR ADC

Hi, layes2,

Can you put any reference about commercial 12 bit SAR Charge-redistribution ADC without selfcalibration?

Thank you,

Uladz55

 

[bear7679]

Re: 12-bit SAR ADC

I don't think 12-bit SAR ADC without calibration is possible. It maybe use laser to modify R or C to meet the spec.

 

[uladz55]

Re: 12-bit SAR ADC

Hi,

Microchip has 12 bit 100ksps SAR ADC (MCP 3204/3208) and nothing mention about selfcalibration.

But I'm not sure they doesn't use selfcalibration.

So, does anybody have experience with or know about 12 bit SAR ADC without selfcalibration?

 

[amraldo]

Re: 12-bit SAR ADC

try maxim

 

[segabird]

12-bit SAR ADC

There is product in Analog Device which is 12bit SAR ADC without selfcalibration. I am sure that.

 

[uladz55]

Re: 12-bit SAR ADC

Hi, segabird,

what Analog Devices's 12-dit SAR ADC without selfcalibration?
Can you put more exact reference?

 

[segabird]

Re: 12-bit SAR ADC

Hi, segabird,

what Analog Devices's 12-dit SAR ADC without selfcalibration?
Can you put more exact reference?

The product ID is AD7450.

 

[uladz55]

Re: 12-bit SAR ADC

Hi, segabird.

Thanks for information.

ADI has AD7440/AD7450 10-bit and 12-bit ADC.
It seems 12-bit ADC without calibration has low yield and ADI used the same circuit for 10-bit and 12-bit ADC.

 

[Mline7]

Re: 12-bit SAR ADC

Theorically, it should be possible to obtain 12bit without calibration on a standard CMOS process.

But we're at the edge of process technology precision, so every device of the circuit must be carefully designed.

My advice is to have a look at P.E Allen's book, which have an intersting chapter on ADC design. From the calculation given on this book, the more suitable architecture for 12 bit SAR ADC without calibration seems to be a charge-scaling MSB, voltage-scaling LSB DAC.

 

[xwcwc1234]

Re: 12-bit SAR ADC

Hi,
I wonder the 12 bits ADC without cal. can have high yield in circuit design point of view. In real IC manufacture , it is difficulty for producing such a product.

 

[uladz55]

Re: 12-bit SAR ADC

Hi,
McCreary and P.Gray stated in their paper (IEEE, JSSC, vSC-10, No.6,1975) that maximum resolution for charge redistribution SAR ADC w/o calibration is 10 bit.
And the main source of unacuracy is capacitors mismatch.

But now we have commercial 12-bit charge redistribution SAR ADC w/o calibration.

Furthermore, A. Hastings in his "The art of analog layout", p.253 in 2001 said, that untrimmed oxide capacitors can achieve 0.01% matching, i.e. 14 or even 15 bit resolution.

So, technology develops very fast.

 

[CDRCDR]

12-bit SAR ADC

Basically as far as I know,10-11bit for the capacitors matching is more reasonable in modern CMOS technology.It is not easy to keep above 12bit resolution.

 

[xwcwc1234]

Re: 12-bit SAR ADC

In aditional to capacitor mismatch, I think there should be other factors affect the resolution up to 12 bits . It may cause by operational amplifier or mos mismatch.