PCA9450CHNY - VDD_SOC resistance to GND

[DanielDs]

Hi,
I'm using PMIC PCA9450CHNY, during bringing-up tests to the board, I see a relatively low resistance to GND.
20 boards were made as POC and all in the same state, in the 20Ω-15Ω region, between VDD_SOC and GND.
I checked other boards we used in the past with this PMIC, boards that work today also the resistance to GND in this area 30Ω-15Ω.
The PMIC is connected directly to the I.MX8MP. Has anyone else encountered these values? Is this normal?
Picture attached with the design, the measure is between TP92 to GND.

[DanielDs]

Thank you all for the replies, it was very helpful.
Daniel

[JozefKozon]

Hi Daniel,

have you measured the resistance with the i.MX8MP connected to the PMIC? If yes, please disconnect the MCU and please measure only the resistance on one components. To see, if the issue is on the PMIC side or on the i.MX8MP side. I have measured the resistance between the LX1 (TP7) and the GND (LK2, LK3, LK4 and LK5) on a PCA9450AA-EVK. I have measured approximately 70kOhm without anything connected to BUCK1. Please check it on your board without the i.MX connected.

With Best Regards,

Jozef

[DanielDs]

Hi Jozef,
Thanks for your quick reply.
I removed R173 and R338(in the picture attached above) to measure the PMIC only and the resistance changed to ~70KΩ.
So, I tried to measure only the i.MX8MP(with bypass capacitors) and I get around 12Ω.
Is that make sense?

[JozefKozon]

Hi Aaron,

thank you for confirmation. So the PCA9450C is ok. I have contacted an i.MX support team to support you. They will answer you in this community thread if the low resistance finding is ok or the i.MX shouldn't have such a low resistance on the VDD_SOC.

With Best Regards,

Jozef

[DanielDs]

Hi, any updates?
Thanks,
Daniel

[riteshmpatel]

Hi @DanielDs,

I had my hands on the i.MX8MP EVK and measured the impedance of the VDD_SOC rail. It was about 16 ohms which is equivalent to the impedance measured by you. So, the impedance value is okay to proceed further.

Thanks & Regards,
Ritesh M Patel

[JozefKozon]

Hi Daniel,

I apologize for a late reply. The previous case seems to be lost. I have created a new case #00536197 and moved it to the i.MX box. Please expect the answer from the i.MX support team soon.

Thank you for your patience.

With Best Regards,

Jozef