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temtronic
Joined: 01 Jul 2010
Posts: 9093
Location: Greensville,Ontario
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 Posted: Mon Jan 25, 2021 9:29 am |
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DS70000689d.pdf, page 491, table 33-56, Param AD17....
It's at the bottom of the page, abover the bold NOTE:....
Jay |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19215
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| Posted: Mon Jan 25, 2021 9:31 am |
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All ADC's have a minimum impedance needed to feed them. The high speed
ADC's on the PIC33's have a much lower recommended impedance for
the source than the older PIC's. Jay has told you the parameter. AD17.
Minimum recommended source impedance... |
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MCUprogrammer
Joined: 08 Sep 2020
Posts: 220
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| Posted: Tue Jan 26, 2021 6:56 am |
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I am looking for an integrated that I will use for reference voltage that can output 3v. I prefer not to have smd. Is there a product you have used before? LM336 didn't do my job.
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MCUprogrammer
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Work Hard |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19215
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| Posted: Tue Jan 26, 2021 7:14 am |
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Problem is that in 3v, 99% of precision VREF devices will be SMD packaged.
There are a few that come in DIP-8 packages.
I use the REF61xx from TI, but this only comes in a 8pin SMD package.
Look at the AD780. Ground pin8, for 3v. However, big question is what
supply you have available?. This needs 4v minimum for 3v out. |
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temtronic
Joined: 01 Jul 2010
Posts: 9093
Location: Greensville,Ontario
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| Posted: Tue Jan 26, 2021 8:29 am |
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| One 'cheat' is to use a chargepump circuit, like I use for running 5V LCD modules on 3V PICs.... to power the precision reference device. It'll add 2 diodes, 2 caps to the PCB ,need 50%+- PWM bit, but should,probably work.... |
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