ADC12D1620QML-SP: Floating Lid

Steve Widener

I have a couple questions regarding the lid and it’s risk associated with spacecraft charging.

Does this package have a floating metal lid, or is it grounded or otherwise electrically referenced?

(I've seen another posting that indicates the lid is floating but there isn't any confirming guidance in the datasheet.)

If it is floating, what is the area of the lid and can it be grounded externally without affecting performance?

Thanks!

over 3 years ago

0 Rob Reeder over 3 years ago

TI__Mastermind 45670 points

Hi Steve,

The lid is not grounded and left floating.

We would not expect grounding the lid to have an impact on the performance of the part.

We did test a similar device, 10b part, with the lid grounded but the results were inconclusive.

We saw a slight degradation in performance but it was within the lot to lot variation of the product.

Therefore, the lid was left floating for this device.

Regards,

Rob

0 Steve Widener over 3 years ago in reply to Rob Reeder

TI__Genius 11010 points

Thanks Rob - Do we have a measure of the area of the lid?

Do you think if we "grounded" the lid through a resistive path, it would improve the Fs/4 spur? Maybe 10kohms for instance?

0 Rob Reeder over 3 years ago in reply to Steve Widener

TI__Mastermind 45670 points

Hi Steve,

I will find out the lid size and let you know.

Please give me a few days as there are many people OOO as you know due to the holidays.

I cannot comment on the resistive path to ground. I think that would make for an odd assembly for the overall system.

Thanks,

Rob

0 Rob Reeder over 3 years ago in reply to Rob Reeder

TI__Mastermind 45670 points

Hi Steve,

See lid dimensions in the datasheet.

Thanks,

Rob

0 Steve Widener over 3 years ago in reply to Rob Reeder

TI__Genius 11010 points

Thanks Rob - I should have seen that in the datasheet mechanicals!

I inadvertently mentioned an Fs/4 spurs but that must have been from a different device I was working on.

For a "resistive" grounding, I was thinking a mechanical spring tab from the lid connected directly to the PCB (threaded inserts). The PCB connection could be to an "Island" flood that would then be routed to GND through the resistor. That path would be enough to keep the lid discharged.

0 Steve Widener over 3 years ago in reply to Rob Reeder

TI__Genius 11010 points

Is there a different recommendation for how this should be mitigated? A 4cm² floating metal lid does present a definite spacecraft charging risk in a lot of orbits.

+1 Rob Reeder over 3 years ago in reply to Steve Widener

TI__Mastermind 45670 points

HI Steve,

Unfortunately, we don't have any current recommendations. I am sure customers have tried what you have suggested above or probably just grounded the lid straight with the lid top directly connecting to the some larger mechanical shield chassis that fits over the CCA, circuit card assembly, itself.

Regards,

Rob

Data converters

Data converters forum

ADC12D1620QML-SP: Floating Lid