Admissible "error" on current reference in corners?

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AMSA84

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Hi guys, I've designed a current reference and I will run PVT corners. My current reference is around 12uA @ 3.3V. It's a Delta Vbe Current reference. Independent of power supply voltage and temperature. I did a CTAT and a PTAT current reference then I summed up.

I'd like to know what is the admissible error when the voltage is at 3.6V and 3V @ -40ºC and 125ºC.

For example, what is the admissible error when we are operating at 3V and -40ºC when compared to 3.3V @ 25ºC.

Kind regards.
 

Hi,

If you don't have a spec at least you know where this reference is used.
Based on the spec of the other blocks perhaps you can define how much this reference can vary.

Regards
 

I would advise you to use MonteCarlo proces+mismatch to determine the accuracy:
1) mismatch can cause additional errors
2) Standard corners do not offer much variation in the BJT's. Often the BJT corner (fast/slow) is correlated with the resistors.
3) min/max values with a given accuary (e.g. +-3 sigma) is more useful than just a min/max value if the distribution has a shape of the normal distribution.

Do you have a calibration/trimming option in your current reference? What about +-3% after calibration?
 

This really derives from the performance of the blocks that
use the reference. If (say) you can tolerate +/-50% slew
rate variation then the reference can be crude. You might
be well off to simulate the performance-critical other blocks
with varying iref and determine the tolerable endpoints of
the distribution, at the corners of your "box".
 

Re: Admissible "error" on current reference in corners?

Nice ideas. I dont have current trimming. Right now my current referente (12uA) has an error around 17% @ 3V -40°C and 21% @ 3.6V 125°C. This was determined by corners. This current is to supply a current to a symmetrical OTA, a comparator with cross coupled load and to a sawtooth generator.

- - - Updated - - -

Nice ideas. I dont have current trimming. Right now my current referente (12uA) has an error around 17% @ 3V -40°C and 21% @ 3.6V 125°C. This was determined by corners. This current is to supply a current to a symmetrical OTA, a comparator with cross coupled load and to a sawtooth generator.
 

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