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LT1790 Voltage Reference — Parallax Forums

LT1790 Voltage Reference

Sal AmmoniacSal Ammoniac Posts: 213
edited 2009-12-06 04:50 in Accessories
Has anyone used this Linear Technology voltage reference? I got two of the 4.096v (LT1790-4096) parts as samples with the intention of using them as Vref for my 12-bit ADC so the transfer function would be 1mV per step.

The input voltage range on these parts goes up to 18v and the dropout voltage is only 50-100mV. I connected these up as shown in the datasheet with a 9v Vin and measured the no-load output on Vout. On both parts I see ~0.335 volts on the output. I was expecting to see 4.096v.

Am I doing something wrong?

Comments

  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2009-12-06 02:52
    Did you put the two·0.1 uf·caps the ones··on the input and output on the regulator and are other end of the caps tied· to ground ·and are·pins 1 and 2 to to ground very importance that this is done or you will get these weird reading that you are getting


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    ··Thanks for any·idea.gif·that you may have and all of your time finding them smile.gif

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    Sam

    Post Edited (sam_sam_sam) : 12/6/2009 3:03:01 AM GMT
  • Sal AmmoniacSal Ammoniac Posts: 213
    edited 2009-12-06 03:09
    Yep, pins 1&2 are tied together and both input and outputs have 100nF caps.
  • kwinnkwinn Posts: 8,697
    edited 2009-12-06 03:43
    Are pins 3 and 6 floating. The spec sheet says do not connect.
  • Sal AmmoniacSal Ammoniac Posts: 213
    edited 2009-12-06 04:47
    Found the problem. When I looked at the connections with a 10x loupe, I noticed that the 100nF cap on the Vout pin wasn't making contact with ground. I fixed that and now see 4.096v on the output.

    Man, those tiny surface mount components are brutal on my 50 year old eyes.
  • FranklinFranklin Posts: 4,747
    edited 2009-12-06 04:50
    I'm seriously thinking of getting a usb microscope sometime soon to keep my face out of the solder fumes.

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    - Stephen
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