[PIC] PIC16F887 > ADC > External Vref of 2.5 V

E

Eric_O

Advanced Member level 4
Joined
May 31, 2020
Messages
105
Helped
0
Reputation
0
Reaction score
0
Trophy points
16
Activity points
1,005
I decided to use an external voltage reference of 2.5 V on AN3 with LM385-Z-2.5.

Regarding the Texas Instrument datasheet of LM385-ADJ, and schematics / formula at page 2, figure 6, when using 5 V for VCC, R2 = R3 = 10 K, and when testing the output voltage at pin « + » of the regulator, without being connected to AN3 of PIC, I never obtain around 2.5 V. I only obtain 1.373 V.

Some one can enlighten me ?

Thanks
 

Attachments

  • LM385 ADJ.pdf
    1.5 MB · Views: 14
  • IMG_7269.jpeg
    1.8 MB · Views: 10

Hi,

it´s not clear how you wired it --> show a schematic. Hand drawn will do. But it should be complete with informations of power supply and ho/where you connected the DVM (both wires)

You said you use the
Eric_O said:
LM385-Z-2.5.
Click to expand...
This already is a FIXED 2.5V voltage reference that does not need resistors to adjust the output voltage. It is preset to output 2.5V!

But you linked a datasheet to LM385-ADJ ... which is the ADJustable version of voltage references. With them you need resistors .. and to adjust the output voltage in a wide range.

--> use the correct datasheet!

Klaus
 

You must log in or register to reply here.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…