ADC of F28377D Delfino Experimenter Kit's control card

yu miao

Other Parts Discussed in Thread: TMS320F28377D

Hi!

I'm using the control card of F28377D Delfino Experimenter Kit. I designed my own docking station for the card.

I met a problem with ADC module.

I used two resisters working as a voltage divider for the AD input of the control card. The designed amplifying ratio is 0.66. The docking station works well without the control card. The ratio stays at 0.66. However, after the control card is installed onto my docking board, some of the ADC inputs's ratios turn into 0.63 no matter how many volts are applied.

I use ADCA0-5, ADCB0-5 and ADCC2-5. The change of the amplifying ratio only happened on ADCA0, ADCA1 and ADCB1. The others work well.

I'm confused and I wonder why.

over 8 years ago

0 Brett Larimore over 8 years ago

TI__Guru 57255 points

Hi,

If you take a look at the descriptions for these pins in the datasheet, you'll notice that they have a "50k ohm internal pulldown".

This should explain what you are seeing.

Thank you,
Brett

0 yu miao over 8 years ago in reply to Brett Larimore

Prodigy 80 points

Thanks very much for your reply.

Would you please recommend the datasheet to me? Because I checked the datasheets of 'spruhm8c' and 'tms320f28377d'. They don't tell which pins have the 50kohm pull-down resistance.

0 Brett Larimore over 8 years ago in reply to yu miao

TI__Guru 57255 points

Hi,

It is at pg15-16 of the current F28377D datasheet (rev F):
http://www.ti.com/lit/gpn/tms320f28377d

The datasheet can be found at the product page (along with the other documentation for the chip):
http://www.ti.com/product/TMS320F28377D

Thank you,
Brett

0 yu miao over 8 years ago in reply to Brett Larimore

Prodigy 80 points

Awesome!
Thanks a lot!

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ADC of F28377D Delfino Experimenter Kit's control card