Hi,
I am using "MC56F8367MPYE" to control the DC motor and works fine for long time.
Then, we produced the new batch of product and have the following problem:
1) When I power on the chip, it causes MOSFET shortage. I checked the reason and found that some pins of PWMA and PWMB are high after power-on. Based on the datasheet, all PWM channels are disabled after POWER ON or RESET.
2) Date code: XAA1315. Can you tell what it means?
We need to know what the exact problem is and how to fix it?
Thanks,
Christie
Hi,
I think it is common practice to connect 10K ohm pull-down external resistor for each PWM pin, during/after Reset, all the PWM pins are in input mode, the pull-down resistor can pull the pin to LOW, which avoid the damage of the power device because of shortening when you set up the power device in a H bridge.
BTW, I suppose you know that you have to add dead time for the complementary PWM signals.
Hope it can help you
BR
XiangJun Rong
Hi,
I think it is common practice to connect 10K ohm pull-down external resistor for each PWM pin, during/after Reset, all the PWM pins are in input mode, the pull-down resistor can pull the pin to LOW, which avoid the damage of the power device because of shortening when you set up the power device in a H bridge.
BTW, I suppose you know that you have to add dead time for the complementary PWM signals.
Hope it can help you
BR
XiangJun Rong
Hi XiangJun,
Thank you for your input. Here are more explanations:
1) It happens on 30% of boards. And these design is used for last several boards and works fine...
2) I have 10K pull-down on all PWM channels.
3) This happens on POWER UP stage, no any software loaded in MCU
4) When I remove MOSFET, no over-current happens.
5) I measured PWM pins, some pins are HIGH. That is the reason causes shortage...
6) I measure the current. When I power ON, it consumes around 130mA, then go up to 160mA, then MOSFET shortage because of HIGH on PWM pins.
I really need your help to see where the problem is and how to fix?
Can I send no function MCU to NXP to confirm?
Thanks,
Christie
Hi,
does the issue only occur on the branch with data code XAA1315?
The issue is that the PWM signal are high during the power-up process before any application code is executed, and the external pull-down resistor can not pull the pin to LOW logic, which leads to MOSFET damage during power-up process.
You can contact local FAE or DFAE, have them to contact failure analysis team.
BR
XiangJun Rong
Hi Xiangjun,
It happens on XAA1315 and XAC1493.
It happens during POWER-UP, no any code is loaded to MCU. The pull-down resistor does not pull down PWM signal.
I am located in Canada, where can I find FAE?
Thanks,
Christie
Hi,
I have contacted AE team, maybe they know if the batch with date code XAA1315 has issue.
I will send you a reply after I get feedback.
BR
XiangJun Rong