TMS570 AD conversion

Lars Guenther

Hi,

I have problems with the AD conversion on my own new developed controller board.
The AD conversion is working fine on my evaluation board TMS570LC43x HDK but not working on my own controller board.

Pins, reference voltage is the same the only difference is the ground pins v19, w18.

I read in the TI documentation (Doc. spns195a, table 3-1 (May 2014))) that the AD Converters need operation supply on Pin w15
and ground supply on pin W16 and w19.
But in the schematic from the evaluation board ( TMS570LC43x HDK) I see that also the pins v19 and w18 have ground supply.

Is the AD conversion running without the ground supply on pins v19, w18 ?

Best regards
Lars

over 9 years ago

0 Bob Crosby over 9 years ago

TI__Guru 72500 points

V19 and W18 are tied together as the input to ADC2[24]. They should not impact the conversion of the other pins. The critical pins are ADREFHI(V15), ADREFLO(V16), VCCAD(W15) and VSSAD(W16, W19).

0 Charles Tsai over 9 years ago

TI__Guru**** 191516 points

Hi Lars,
You don't need to connect v19 and w18 to ground for ADC to work. v19 and w18 are for ADC1IN[24] in LC4357. The HDK board is shared between LC4357 and LS3137 device for which the v19 and w18 are tied as VSSAD.

0 Anthony F. Seely over 9 years ago in reply to Charles Tsai

TI__Guru 68920 points

Just to add something. There is a reason why we've got some of these redundant balls.

For the pins on the corner of the package - where there is duplication - the reason is for reliability. The corner balls on the BGA are subject to more stress than the others - so if we duplicated a corner ball please do wire them all together on your board. That way if one ball opens up due to stresses - you still have the redundant ball there to keep the connection made.

0 Lars Guenther over 9 years ago in reply to Anthony F. Seely

Intellectual 675 points

Hi all,

I found my error, do not connect VCCAD to GND.

Thanks

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TMS570 AD conversion