RT1050启动不了

[haifeng_jin]

hi  最近在测试RT1050启动的时候，有非常低的概率出现RT1050启动不了，硬件电路是按照demo设计的，Pswitch也做到了延时，但是出现问题的时候，CPU的1.2V没有输出，不知道应该会是哪里的问题？

[weidong_sun]

Hello Haifeng,

    这个问题基本上还是由于内部DCDC输入和输出之间的延迟造成的，如果在PSWITCH上使用30K电阻，0.22uF的RC延迟，那么继续调高延迟时间做实验：0.22uF增加到1uF，增加电容的充电时间；也可以同时增加30K到47K，继续增加充电时间。

    除了上述方法，没有更好的方法去解决这个问题。

This problem is basically caused by the delay between the input and output of the internal DCDC. If the RC delay of 0.22uF and 30K resistor are used in PSWITCH, then continue to increase the delay time: 0.22uF to 1uF, increase the charging time of the capacitor; at the same time, increase the charging time by 30K to 47K, and continue to increase the charging time.

In addition to the above methods, there is no better way to solve this problem.

Have a nice day!

BR,

Weidong

[haifeng_jin]

现在发现了现象是外部供电有快速跌落又马上上来的，跌落时间在10-60mS时间不等，那个时候，Pswitch还在放电，然而POR已经变低，然后马上上电，导致了时序没法保证，导致了启动不了，这个好像没法解决。

[weidong_sun]

Hello Haifeng,

>>现在发现了现象是外部供电有快速跌落
不知道是DCDC3.3V跌落，还是外部供电的5V有跌落，都要花时间查一下原因。

正常的上电顺序应该是这样的：

（1）LDO_3V3
（2）DCDC_3V3 （由LDO_3V3 enable DCDC_3V3）
（3）SOC_IN （这是1.1V~1.2V核心电压，在DCDC_3V3 输出2ms后输出给MCU core供电）
（4）三个电压稳定后，复位芯片给出MCU复位信号（也就是Power On Reset）

所以，对出现问题的板子，查找一下原因。

我在I.MXRT1050 EVK上多次试验后，也没有复现这个问题。

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>>It is now discovered that there is a rapid drop in external power supply.
I don't know if DCDC3.3V or 5V of external power supply has fallen, so take time to find out why.

The correct Power on Sequence should be as follows:

(1) LDO_3V3

(2)DCDC_3V3 ( LDO_3V3 enable DCDC_3V3 )

(3)SOC_IN ( This is 1.1V~1.2V core voltage, which is output to MCU core after DCDC_3V3 outputs 2ms. )

(4)After three voltage stabilities, the reset chip gives the MCU reset signal (that is, Power On Reset)

So, for the problem board, find out the reason.

After many tests on I.MXRT1050 EVK, I did not re-produced the issue.

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Have a nice day!

BR,

NXP TIC Weidong Sun