Minimum load for 3V voltage reference?

[Flyback]

Hello,

I wish to use the MCP1703 voltage regulator to produce a 3V reference voltage from a 3.3V rail.
(it will provide the reference voltage for a microcontrollers ADC reference input)
What is the minimum load current that i need to load the output with in order to get the output voltage accurate at 3V?
The datasheet graphs seem to show a minimum current of 1mA flowing.
What will the accuracy be like if only 100uA flows?

MCP1703 datasheet
https://www.electro-tech-online.com/custompdfs/2013/06/22049f.pdf

 

[ronv]

I don't see anything that says it won't work, but I think I would use a shunt reference like the LM4041. Better initial accuracy and much better specs at your load. Probably cheaper?

 

[jjw]

MCP1703 has at 3.3V Vin typical dropout voltage 525mV and maximum 725mV, so if you need accurate 3V reference voltage, it won't work.

 

[Flyback]

that 525mV is for 250mA supply current, this will be supplying one mA or less....hopefully less.......but thats what i dont know from looking at the datasheet.

 

[ericgibbs]

that 525mV is for 250mA supply current, this will be supplying one mA or less....hopefully less.......but thats what i dont know from looking at the datasheet.

hi f,
Read my reply on your other thread
https://www.electro-tech-online.com/threads/common-mode-input-range-of-opamp.134960/

E.

 

[Flyback]

Thanks, i read that, but with MCP1703, on page 7 of the datasheet they have graph 2-13 which shows dropou voltage less than 0.1V for less than 10mA output current.

 

[kubeek]

Then I guess you have to try it, but keep in mind that it is just a regulator, not a precision reference.

 

[Flyback]

Yes, though its accuracy of +/3% from -25c to 125c is good enough for our needs (+-0,4% at 25c)

 

[ronv]

I think what bothers every one is why you would want to use a poorly spec'd part for your application when there are available parts with worst case specs for about the same size and cost?

 

[blueroomelectronics]

I think what bothers every one is why you would want to use a poorly spec'd part for your application when there are available parts with worst case specs for about the same size and cost?

There's that.

Many modern MCUs designed to work with analog stuff have built in precision voltage references for just this reason.

PS why not use a precision shunt regulator like the popular TL431?

PPS Flyback, who is specking the parts for your design? They all seem like really odd choices for an emergency lighting system.

 

[Flyback]

the ADVREF pin of SAM3N takes 250uA so with TL431 we get loss in the resistor that it needs.....MCP1703 needs no resistors, just the regulator itself, so it will be less lossy and easier on the battery in long mains outages.
Ths software guy chose the sam3n

 

[blueroomelectronics]

I'd think the least of your power consumption worries are going to be the voltage reference.

 

[ronv]

Then take a look at the LM4040 here:

Big savings!

https://www.mouser.com/Semiconducto...nces/_/N-6j76i?P=1z0j46kZ1z0wd7g&Ns=Pricing|0

 

[blueroomelectronics]

Then take a look at the LM4040 here:

Big savings!

https://www.mouser.com/Semiconducto...nces/_/N-6j76i?P=1z0j46kZ1z0wd7g&Ns=Pricing|0

Nice part, although it still uses a resistor and the OP doesn't want that.

 

[ronv]

Yea, But it only takes 65 ua. instead of his 250 - so almost 4X better. Sorry, just being a ---