Seems that as supplied, the power supply capacitance design on the MPC5746R 252 daughtercard is borderline.
Test procedure - set the board to use the MB 1.25_SR as the source for the core:
Daughterboard:
J19 = open
J17 = open
J18 = 1-5
MPC57XXMB Motherboard:
J60 = open
#1
Power up.
Processor boots ok.
#2 Now replace the J18 shunt with a length of wire, say 70mm long.
Power up.
Processor is stuck in reset.
PORST is off. Scoping the RESET line shows a 50% duty 121Hz signal.
#3
Add a 4.7u capacitor between TP16 and TP18
Power up.
Processor boots ok.
The schem shows a number of non-pop 4.7u caps on VDD_LV_CORE - why ? I suggest these be populated in future builds.
Test #2 is similar to using a off-board 1.25 regulator.
regards
James
Hi,
Hmm, usually the EVB boards are made with great reserve in case of design.
I will try to get feedback from application engineer.
regards,
Peter
Any news ?
James
Any news?
Hi,
I have sent your questions to application engineer.
But up to now I didn't get any response.
I do not expect that he will unless this is entered as ticket to our system trough web site.
Since I am general support I am not able to answer all technical details for HW.
I suggest you to write official ticket on nxp.com, or try to contact the sales/ FAE assigned to your company or distributor to speed this up.
regards,
Peter
Thanks for your reply. I have created a case no. 00264903