Filtering Capacitors on Externally Connected Pins

[peter.davis]

Hello,

On he C-SiP package, there are several externally expose pins that are either connected to each other or brought out that serve key functions. For example:

1. PMIC_NRESET
2. PMIC_PB_IN
3. PMIC_POWER_EN tied to PMIC_PWEREN
4. PMIC_LDO_PGOOD tied to RTC_PWRONRSTN
5. PMIC_NINT tied to EXTINTN
6. PMIC_NWAKEUP tied to EXT_WAKEUP
7. PWRONRSTN tied to PMIC_PGOOD
8. PWRONRSTN_OD tied to WARMRSTN

Do these connections have filtering capacitors and strong enough pull-ups such that they will be immune to noise that could cause a false logic low/high? Is there a concern with adding filtering capacitors to these pins, such as 0.1uF or less?

Thank you,

Peter

[Neeraj Dantu]

Peter,

Pins that can have buttons on them such as PMIC_NRESET and PMIC_PB_IN can utilize a small capacitor for de-bouncing, but the other signals you list are very low frequency and often only change levels once after reboot.

For convenience, the pins that need to be connected are brought out to SiP pins that are adjacent. This minimizes the cross talk. So, caps on these pins are not required. Please note that poor stack-up and routing can always cause issues with the board that can effect these signals, but as long as reasonable layout practices are followed, there is no need to be worried about these signals.

Best,

Neeraj

[Author]

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