MPC5634M with high power consumption,How to solve?

[liujian]

(1) please tell me ,the voltage  of Q2 , B and E ？

and  i find  the  graphics of the base of the Q2   is Sawtooth wave.

（2）R18 C20， R25C28   What is their role？

（3）C39,How to choose the capacitor materials?

(4)When I put the two removed after the chip ,power consumption become normal.

[liujian]

I used the values of the datasheet,but was  invalid,I thought the reason that  was not the nets of the V1.2V

the main reason is VRC3.3V. when I  removed  C39,C40 from the MCU,  Power consumption is normal, if not ,the mcu very very hot.

Attachment is my complete designed curcuit.

[lukaszadrapa]

Hi,

I have to suggest to use recommended values listed in datasheet.

Did you check if C39 and C40 are OK? The capacitors could be shorted or maybe there's a shortcut on the board.

It is also good idea to replace also the MCU because it can be already damaged.

Lukas

[liujian]

Hi

C39 and C40 must be good because I changed a lot. I have three versions circuit board as same phenomenon.The MCU is used by a batch. Maybe the problem is in the MCU ?

migliu

[lukaszadrapa]

Hi,

I have checked the schematic again but I can see nothing obvious wrong. Notice that I checked only the pdf version. I can't open the files in rar archive.

What is the voltage level on VRC33 pin when it works / doesn't work?

Lukas

[liujian]

(2) if I used the  recommended value of  R18 C20， R25C28 in the TRKMPC5634MSCH, I f ound  the waveform of the  base of  the Q2  was not smooth, unless  I use the value  :    C20 = 0.22uf. the value is too big  I think.

(4)  when I  removed  C39,C40 from the MCU,  Power consumption is normal, if not ,the mcu very very hot, Attachment is my designed curcuit

[lukaszadrapa]

Hi,

I can see that the capacitor values in TRKMPC5634M does not correspond to values stated in datasheet.

http://www.nxp.com/files/32bit/doc/data_sheet/MPC5634M.pdf

See the chapter 4.6.1 Regulator Example.

It looks like the TRK board was designed in early stage of MPC5634M development, so it does not follow the latest spec.

Please follow the recommended values in datasheet.

Regards,

Lukas

[liujian]

Hi:

I used the values of the datasheet,but was invalid,I thought the reason that was not the nets of the V1.2V

the main reason is VRC3.3V. when I removed C39,C40 from the MCU, Power consumption is normal, if not ,the mcu very very hot.

Attachment is my complete designed curcuit.

migliu

[liujian]

I used the values of the datasheet,but was  invalid,I thought the reason that  was not the nets of the V1.2V

the main reason is VRC3.3V. when I  removed  C39,C40 from the MCU,  Power consumption is normal, if not ,the mcu very very hot.

Attachment is my complete designed curcuit. !

[lukaszadrapa]

Hi,

1. Voltage on emitter is 1.2V, voltage on transistor base depends on regulator loop.

2. Snubber - Wikipedia, the free encyclopedia

3.

Ceramic resistor is OK.

4. I'm not really sure what do you mean. Could you provide more details?

Regards,

Lukas