Hello,
I hava a problem with my Custom PCB. My code and system works well until I turn ON and OFF power supply supplying ImX.
The power supply of my custom board is the same as mimxrt1170-EVKB Reference Design. I added one Reset Supervisor UmM803RS IC for POR_B and one UML805 for turning off 5->3.3V conveter by making LOW , PMIC_ON_REQ signal. UML805 IC monitors VDD_SNVS_IN. I also used a separate Regulator for SNVS first turnout same as in the reference EVK Design.
When I open and close the power supply with 5-10sec short intervals, it works well. However when I continuously press ON OFF button of Power supply, imxrt1176 does not boot and it gets stuck. I added a working LED for observation. So when fast ON-OFF, LED does not toggle. At this stage, I am monitoring that power supply is 13.5V and current drawn is 0.12Amps. I suspect that Power Supply might not give enough current and may somehow interrupt giving output current at this situation. So I added a power resistor in parallel to product while this problem has occured and saw that Voltage is 13.5V and Current is 1.12Amps. So I see that Power Supply is OK and has no interruption.
In addition to above, I measured voltages 5V, 3.3V,1.8V and Pmic_Req_On signal levels on PCB. All voltages seem OK. However as I said, the code is not run. It seems that IMX would keep itself into protection.
What might it be the cause? Where will I focus to solve those problem?
My product needs to be run no matter how quickly I open and close the main power.
You are welcome, I'm very glad to support you in solving your problem.
Hi @mayliu1 ,
I performed lots of tests with MIMXRT1170-EVK during last Friday.
I performed 5 different settings according to the "SPF-32171_C3.pdf" schematics document.
1st Setting:
- U47 Pin Number #1 is disconnected from the PCB
- On-Float Pin#1 of U47 is connected to the P3 pin of IMXRT1176, which you recommend to pull LOW of DCDC_PSWITCH. I soldered pin#1 in place of R395 intersection point with R396.
- Pin Number#2 of U356 is soldered to the IMXRT1176 #DCDC_PSWITCH pin.(R1900 and R1899 not populated and left as it was.)
2nd Setting:
- Only 0R was soldered to the R1899 and R1900. So just want to observe what happen when only External Reset Circuit was used.
3rd Setting:
- Pin numbered #2 od U356 is soldered to the R395 cross point with DCDC_PSWITCH pin of IMXRT1176. (Just to observe what happens if only switching DCDC_PSWITCH pin.) Again, R1900 and R1899 not populated and left as it was.
4th Setting:
- pin #1 of U39 (PG), which in case TP32 Point, was soldered to the DCDC_PSWITCH pin of IMXRT1176.
I faced the same problem only with the 2nd setting . Other remaining Settings got worked. I could not repeat the issue with them all. So your suggestion to pulling DCDC_PSWITCH TO Low is true and solved the issue seemingly.
Thank you very much for your invaluable helps.
BR, Burhan
what must the trigger of Base of transistor be? As based on MIMXRT1170-EVK schematics, Should I trigger base with VLDO_3V3 or VDD_3V3 OR DCDC_1V8_OUT voltage? Which one is best suitable to pull LOW of DCDC_PSWITCH pin?
Thanks a lot
Thanks for your updated information.
I suggest you can add a transistor in the simplest way. For your other questions, I advise you to create a new case, and our team will do our best to support you.
Best Regards
MayLiu
Thank you for your quick return:
I want to ask that can I use the below Supervisor circuit ? If I connect RESET pin of below SS circuit to the directly Pin#2 of J77 Connector in your response post; Will it be the correct way to discharge DCDC_PSWITCH pin of IMXRT1170?
Or If I alternatively decide to use any Mosfet to Pull DCDC_PSWITCH low; Should I apply 3.3V SNVS_IN voltage to trigger the mosfet gate? Or something different voltage that I have to use for triggering?
As a second question, in MIMXRT1170-EVK board, there are 2 different Supervisor IC. I am planning to use only UM803RS instead of UM805RE IC? I will use UM803RS to keep Pmic_REQ_ON signal to LOW and thus disabling 5V to 3.3V Converter IC. In eval board, UM805RE does this job. Since I do not need any MR pin, UM803RS seems enough for my task. Does it cause any problem to me later?
Thanks for your invaluable helps,
BR, Burhan.
Thanks for your updated information.
I checked your question, I have reviewed the document materials written by an expert in the relevant field.
I think the possible reason as follows:
The short period of power-down and power-up disrupts the power-on sequence (the timing of DCDC_PSWICTH) of the RT chip, finally , it leading to an error in the state of the RT chip's DCDC and causing it to lock up.
I will take MIMXRT1170-EVKB board as example:
When DCDC_PSWICTH is high, the DCDC begins to operate.
The correct timing should be as follows: when 3.3V is applied to DCDC_IN, due to the presence of C286, the 3.3V charges C286, resulting in DCDC_PSWICTH being pulled high about 2ms later than DCDC_IN.
This is done to ensure that the actual input voltage at DCDC_IN reaches a steady state of 3.3V before enabling the DCDC module to operate.
Regarding your case:
During a short power-down and subsequent power-up, the interval between the two is too short.
As a result, during the second stage of power-up, C286 does not have enough time to discharge, it causing DCDC_PSWITCH to remain high.
This can enable the DCDC module before the actual input voltage at DCDC_IN reaches the normal operating voltage range of the DCDC, leading to the DCDC state machine becoming locked.
At last, the solution is to make sure that the voltage at DCDC_PSWITCH is below 0.5V before each power-up.
Therefore, after each power-down, it is necessary to quickly discharge C286 to 0V or quickly pull DCDC_PSWITCH low to 0V. The general recommended approach is to add a transistor or a voltage monitoring chip to achieve this effect.
Wish it helps you.
If you still have question about it, please kindly let me know.
Wish you a nice day!
Best Regards
MayLiu
Actually, MIMXRT1170-EVK has suffered the same problem. Even though, power supply(+5V) exists and can give current on demand, MIMXRT1170-EVK does not demand/draw any current after some manipulations.
Attached is a short video. Pls watch till the end of video showing I am getting the issue. The error happens at 1.27 seconds and later, after power ON/OFF cycle the eval board, it returns to normal working state.
I repeated the issue 5-6 times within 20 minutes with eval board. When issue happens, I connected a power wattage resistor to draw current from Power Supply in order to be sure hat PS can give current in case demanding. PS gave the current without problem.
So, the EVK can not reset and work as you see. So my custom PCB has very very similar power circuits as in the EVK schematics.
How can I fix/solve this problem? The board must work every time power enters into it. I actually supply my product with car battery. Car battery does not give smooth voltage/current every time it opens. Besides it, in the field, more unpredictable things may happen, and it causes my board not to work. Therefore, I did try to simulate car battery behaviours.
Thank you so much for your interest in our products and for using our community.
Regarding this "In addition to above, I measured voltages 5V, 3.3V,1.8V and Pmic_Req_On signal levels on PCB. All voltages seem OK. However as I said, the code is not run. It seems that IMX would keep itself into protection."
I suspect that it is related to the reset timing sequence. Please use an oscilloscope to capture the timing diagram of the pins in the following figure. Additionally, check for signals glitches and stability on these pins.
Wish it helps you.
If you still have question about it, please kindly let me know.
Wish you a nice day!
Best Regards
MayLiu