AM263P4-Q1: ADC_CAL Pins

Lewis Maikos

Part Number: AM263P4-Q1

Hi,

Datasheet states that the ADCs are calibrated at the factory during production. Therefore I do not wish to use the ADC calibration function. Is it valid to then connect all of those pins to ground in my design? (ADC_CAL0, ADC_CAL1, ADC_CAL2, ADC_CAL3)

2 months ago

0 Fleenor 2 months ago

TI__Mastermind 35653 points

Hi Lewis,

Yes, connecting ADC_CAL0 and ADC_CAL1 to ground is valid — but with an important condition. The datasheet's Pin Connectivity Requirements section explicitly states:

"If all ADCx_AINy inputs for all ADC instances (ADC[0:4]_AIN[0:5]) are not used, the ADC_CAL[0:1] analog pins must be connected (shorted) directly to ground (VSS)." [1]

This means grounding ADC_CAL0 and ADC_CAL1 is not just valid but required when you're not using any of the ADC analog input pins. However, if you are using any ADC_AIN inputs in your design, be aware that ADC_CAL0 and ADC_CAL1 are shared with ADCIN6 and ADCIN7 across all five ADC instances [2]. Grounding them in that case would tie those analog input channels to a fixed potential.

Pin	Ball	Package Availability	Grounding Guidance
ADC_CAL0	U16	All packages	Ground if all ADC[0:4]_AIN[0:5] unused [1]
ADC_CAL1	T15	All packages	Ground if all ADC[0:4]_AIN[0:5] unused [1]
ADC_CAL2	U17	ZCZ_S and ZCZ_F only	Not explicitly covered in grounding requirements [3]
ADC_CAL3	N17	ZCZ_S and ZCZ_F only	Not explicitly covered in grounding requirements [3]

Important notes:

ADC_CAL2 and ADC_CAL3 only exist on the ZCZ_S and ZCZ_F package variants — not on ZCZ_C [3]. Verify which package you're using.
The Pin Connectivity Requirements table explicitly addresses ADC_CAL[0:1] but does not explicitly list ADC_CAL2 or ADC_CAL3 with the same grounding instruction [1]. For ADC_CAL2/3, you should follow the general rule that any unused ADC_Rx_AINy input must be connected directly to ground (VSS) [1], since these pins are shared with ADC_R instances.
I will file an internal ticket to have the Pin Connectivity Requirements to include ADC_CAL[2:3] instructions.

Recommendation

If you are not using any ADC analog inputs at all, ground all ADC_CAL pins present on your package. If you are using some ADC channels but not the calibration function, you should still ground these pins since they map to ADCIN6/ADCIN7 channels you won't be using — and the datasheet requires unused ADC input pins to be shorted to VSS [1].

To help refine this recommendation, it would be helpful to know:

Which specific package variant (ZCZ_C, ZCZ_S, or ZCZ_F) you are designing with — this determines whether ADC_CAL2/3 are present
Whether any ADC inputs (ADC[0:4]_AIN[0:5]) will be used in your design
Whether your design uses the ADC_R (resolver ADC) instances that share ADC_CAL pins

Best Regards,

Zackary Fleenor

+1 Lewis Maikos 2 months ago in reply to Fleenor

Prodigy 10 points

Hi Zackary,

Thanks for the detailed and helpful response.

Currently in my design I am using all ADC channels, including all the resolver ADC (RDC) channels. Therefore, leaving all ADC_CAL pins unconnected rather than grounding them would be the correct approach? Could you kindly confirm if this is the case?

Note: I'm designing for the ZCZ_S package.

Kind Regards,

Lewis

0 Fleenor 2 months ago in reply to Lewis Maikos

TI__Mastermind 35653 points

Hi Lewis,

Yes, leaving all ADC_CAL pins unconnected is the correct approach for your design. Since you are using all ADC channels including all resolver ADC (RDC) channels on the ZCZ_S package, you should not ground the ADC_CAL pins. Here's why:

The ADC_CAL pins are physically connected to the ADC multiplexer — ADC_CAL0 and ADC_CAL1 map to ADCIN6 and ADCIN7 across all five ADC instances [1][2], while ADC_CAL2 and ADC_CAL3 can be selected as resolver ADC input channels (via CHSEL values of 4 and 5 in the ADC_R_ADCSOCxCTL registers) [3]. Grounding these pins while actively using the ADC and resolver channels would tie shared analog inputs to a fixed potential, causing signal interference with your active conversions.

The datasheet's grounding requirement applies specifically to the case where ADC inputs are unused — since yours are all in active use, that requirement does not apply to your design.

Summary for your ZCZ_S design:

Pin	Action	Reason
ADC_CAL0 (U16)	Leave unconnected	Shared with ADCIN6 across ADC[0:4] — in use
ADC_CAL1 (T15)	Leave unconnected	Shared with ADCIN7 across ADC[0:4] — in use
ADC_CAL2 (U17)	Leave unconnected	Shared with resolver ADC inputs — in use
ADC_CAL3 (N17)	Leave unconnected	Shared with resolver ADC inputs — in use

One additional note: The "ADC_CAL" naming is somewhat of a misnomer — these pins are not connected to calibration circuitry in the way the name suggests, but rather serve internal purposes while sharing physical routing with the ADC MUX [2]. The factory calibration you referenced in your original question is a separate mechanism and does not depend on these pins being connected in any particular way.

Best Regards,

Zackary Fleenor

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