how to generate a ramp voltage on a soc

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stud.taneja

Newbie level 6
how do we generate a ramp voltage for comparator offset voltage calculation on a SOC for analog built-in-self test application?

erikl

Super Moderator
Staff member
Constant current into and out of a capacitor.

If your SOC includes a DAC anyway, you could use it together with a (slow) clock and a binary counter, s. this posting!

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stud.taneja

Newbie level 6
but that would create discrete voltage levels

is there any way to generate a perfect ramp without using complicated circuits

erikl

Super Moderator
Staff member
that would create discrete voltage levels
Does it matter if you have a fine resolution?

is there any way to generate a perfect ramp without using complicated circuits
Sure; told you above!

Another way: A SOC surely has a clock. Divide it down to an appropriate frequency and integrate it to a triangle ramp.

stud.taneja

Newbie level 6
yes it does matter a lot as i have to measure the comparator offset voltages which are in mV

integration thing is OK but it will require a cap which will bring a large area

erikl

Super Moderator
Staff member
yes it does matter a lot as i have to measure the comparator offset voltages which are in mV
There are DACs with sub-mV resolution. Seems you don't have one, poor guy!

integration thing is OK but it will require a cap which will bring a large area

Depends on your comparator speed: 10nA/10pF = 1mV/µs could be a compromise.

Otherwise use my 3rd suggestion: slow clock integration.

stud.taneja

stud.taneja

Points: 2

stud.taneja

Newbie level 6
we do have a dac with sub-mV threshhold but i need one for high frequency interfacing (250 MHz - 500 MHz) . Are such DACs available

---------- Post added at 15:48 ---------- Previous post was at 14:56 ----------

also tell the possibility of generating a sine wave using PWM

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