RT1176 Problem connecting some power rail

[Tariq_Al]

Hello Everyon,

I am developing a custom board based on MIMXRT1176CVM8A, and unfortunately, I could not bring the board alive via UART or JTAG. 

During my troubleshooting, I found that I had mistakenly connected the +VDD_LPSR_DIG with +VDD_SNVS_DIG.

My question is, could this be a problem preventing the device from booting? 

To be noted, I have done the power-on sequence correctly, but regarding the internal DC-DC, I couldn't get a 1.0V for the IN_SOC. I don't know if this problem is also related to my mistake, so I have connected an external power supply for the core voltage. 

Thanks a lot..

[Tariq_Al · Accepted solution]

Thank you @diego_charles.

Sorry for the late response. 

I did not design any external DC-DC IC converter to supply the 1V0. 

However, I supplied the 1V0 through the external power supply, and it worked! The board is functional correctly, booting, and communicating serially.

I appreciate your support. 

[diego_charles]

Hi @Tariq_Al 

I am very glad to know  that your custom design is now working! I wish you good luck in the upcoming stages of development. 

Diego

[diego_charles]

Hi @Tariq_Al 

Thank you for reaching out! 

Both VDD_LPSR_DIG and VDD_SNVS_DIG are LDO outputs that ramp-up independiently and each one have a different typical voltage  (1v and 0.85v respectively ). I can not tell if this shortcircuit  is the origin of your issue, but after separating them do you see any diferrence? Please do that and use the recommended capacitors on these pins as seen on our EVK. 

Diego

[Tariq_Al]

Thank you for your replay. 

Actually, I have connected using polygon in internal layers, I could though saperate them by cutting the trace, but I can not put the output capacitors, would it be a problem?

[diego_charles]

Hi @Tariq_Al 

My apologies for the delayed response. Adding those caps is our recommendation to ensure that the design is robust. So I can not tell rigth away if not having them could be discarted. 

Let me know if you found out anything else during the troubleshooting.

Diego

[Tariq_Al]

Hi,

I disconnect the two power rails, and now I got these voltages: 

VDD_SNVS_ANA = 1.79V

VDD_SNVS_DIG  = 0.03V

VDD_LPSR_ANA = 1.8V 

VDD_LPSR_DIG  = 1.01V 

DCDC_DIG = 0.64V ! 

VDDA_1P0 = 0V ! 

I am not sure why my DCDC_DIG output is still 0.6V and the VDDA_1P0 is 0v  !!

Note: I Disconnected them on another board because I was afraid the board got damaged, so the above results are from the new board.

[diego_charles]

Hi @Tariq_Al 

I am sorry for the delayed response, Have you found something else in the meantime?

By looking at the values you measured, have seen the below issues.

VDD_SNVS_DIG  = 0.03V  : I see that this LDO output is still not generating power. This LDO depends on the VDD_SNVS_IN. 

I am concerned about this LDO output being 0v as well. How does the power-up supply ramp looks?

DCDC_DIG = 0.64V ! : The digital  output of the DCDC is not generating the expected power, but the analog does ? What is the voltage of DCDC_ANA?

VDDA_1P0 = 0 v: This LDO output gets power from DCDC_ANA.  if DCDC_ANA is not generating the expected power this failure could made sense.

How does your DCDC external circuitry looks?

Thank you very much for your patience. 

Diego