I would like use ADP1762 adjustable LDO.
My application needs power supply +0.975V +-0.025V (≙ accuracy 2.56%) at 1.7A.Supply voltage tolerance sourced to LDO input is +1.8V +-0.1V.Ambient temperature definition from 0°C to +40°C.
How I have to calculate LDO output voltage tolerance?Is it possible to achieve requirement with ADP1762 adjustable device?Do I need Radj with less then 1% tolererance?
My worst case tolerance calculation resulting in more then 4% exclusive Radj tolerance.
It seems to be unusual much.
Hi,Output voltage accuracy of ADP1762-ADJ is affected by the adjust resistor (RADJ), adjust current (IADJ) and the ADJ gain factor (AD).
VOUT = RADJ x IADJ x AD
At worst case conditions, VOUT accuracy is computed as:
You are right that it would reach approximately ±4.0% worst case tolerance and this is typical in ADJ models because of different sources of errors introduced to the LDO.
I suggest you apply an output voltage margining to ADP1762-ADJ and set your VOUT nearer to 0.975V to achieve your desired accuracy for your application. You can refer to this article to guide you in designing your voltage margining circuit: “Voltage Margining Made Easy”