MPC5744P-SCH

[chenxiubo]

Hi, 

      I  am designing  MPC5744P Schematic,  includes  MPC5744P minimum system and power system.  While I 

got the PCB, and started to power.  I  found  it does not work well: Q1(BCP68)  cann't  covert  3.3 v  to 1.25v, after

30 seconds  the MPC5744P mcu  got hot.

     I checked the  Schematic and not find any wrong. Are there  something wrongs with the capacitance value  or  inductance value?  Or are  there  some pins should pull up or pull down?  LM2596-5  or  AMS1117-3.3  is  not  power

enough for MPC5744p?  

[petervlna]

Hi,

I have check it and I can say not a single decoupling capacitance pair is correct.

Did you followed MPC574xP Hardware Design Guide?

And I can see in your schematics is used MPC5643L.

Peter

[tony_huang]

Hi,

Yes, basically MPC5643L is pin to pin to MPC5744P . I have a demo board for MPC5643L, and I placed MPC5744P instead of  MPC5643L previous in the PCB board,  and downloaded a project,it goes well.

1. Are there  some pins should pull up or pull down?  

2. LM2596-5  or  AMS1117-3.3 is suitble for the power?

[petervlna]

Hi,

You said your micro is getting hot and also that ballast is not generating 1.2V. This is because you are either applying voltage on pin where it not should be or by wrong design of power circuits. And your balast is not generating 1.2V. I will start here to check why.

As I said, if you check MPC574xP Hardware Design Guide you will see that your system is not designed for MPC5744P. Your decoupling capacitance is violating our recommendations.

A1: unsused pins should be on defined level. (GND or VDD) to reduce EMC.

A2: I see no issue if the can provide max required current by datasheet.

Peter

[chenxiubo]

Hi,

        Now I only need  to replace  these  decoupling capacitance in  the  MPC574xP Hardware Design Guide  recommend.

Thank you very much.