What is the processing of unused pins of MKM14Z64ACHH5?

[jun1]

hi,

I am using MKM14Z64ACHH5.
The following pins are unused, but are terminal processing open? Should I pull it up or down?
Also, where is the explanation of functions such as SDADP 0 written in the manual?

PIN name
 8    XTAL 32K
 9    EXTAL 32K
11   WKUP
14   SDADP0
15   SDADM0
16   SDADP1
17   SDADM1
20   SDADP2/CMP1P2
21   SDADM2/CMP1P3
24   SDADP3/CMP1P4
23   SDADM3/CMP1P5

Thanks

[miduo · Accepted solution]

Hi,

For XTAL32/EXTAL32, they are dedicate analog pins, we recommend just floating them if do not used.

For WKUP pin, the default for RTC_CTRL2[WAKEUP_STATUS] is 00, that means the pin is in Hiz mode after reset. So you can leave it open if would not use it.

And the SDADP0/M0, SDADP1/M1 are the AFE module differential channels input pins. If not used, can been left open.

[jun1]

Thank you for your instruction.

Because it is influenced by noise, I was thinking about pulling down and pulling up the input terminal.
What is the good reason for opening as a circuit?

（I am sorry that my English is not good）

[john_suchyta]

Hi Jun,

The analog input pins are not influenced by noise when they are not used (not enabled as analog inputs). The EXTAL32 pin does not have a digital input buffer that is affected by a mid-rail level. The same is true for unused digital pins that are in their default condition (MUX=000). The digital input buffer is not connected, so a floating level on the pin will not cause partial turn-on of the input buffer.

The best reason to avoid using external components to bias unused pins is that this takes up board area that can be used to improve grounding or signal routing for other pins.

Regards,

John