[solved] PIC18F66J94 and Vcap/Vddcore connected to Vcc ?

[spilz]

Hello
I’m still working on a new device for me : PIC18F66J94
And I have some issue : sometimes it doesn’t start properly and I have to turn on and off power two or three times before it start normally.

Configuration : quartz 16MHz

[Ttelmah]

Chips with the VddCore pin, need a 'piggyback' board to be programmed
with programmers like the PicKit3.

You need a board that holds the PIC, has the capacitor to VddCore, and
then has an ICSP header to connect to the PICKit3, and generates the
3.3v to feed the chip (2v to 3.6v max).
Look at figure 2.1 in the data sheet. Minimum connections.

The capacitor on Vddcore, needs to be very close to the chip, and a low
ESR type. The datasheet will tell you the recommended types. X5R or X7R.
Vddcore runs at 2.5v max (1.8v) fed from a regulator inside the chip. If you
connected the core to 3.3v, then you risk damaging the chip.
Some chips have the option to run off a low voltage like 2v, and disable
the internal regulator. This one doesn't.

[spilz]

Thanks for your very quick reply

I checked again, I did the minimum connections as in 2.1
I set a 10uF tantium low ESR at 8mm (can not be closer as it’s a generic pcb for TQFP before design the futur PCB)

I understand for Vcap on 3.3V to program it

But I just test it again :
Vcap connected to 3.3V -> pic run normally
Vcap not connected to 3.3V -> pic doesn’t seem to start ...

[Ttelmah]

You have got the ENVREG pin connected to Vdd?.
This is _required_....

No, I don't think yours has this pin, so the regulator should be permanently
enabled. It almost sounds as if you may have destroyed the regulator...

[spilz]

I’m maybe dumb but I don’t find this pin ...
/MCLR is connected to Vcc with 2 resistors and a cap as shown in 2.1

[spilz]

How can it be destroy if it should be connected to 3.3v to be programmed ?
It shouldn’t be 3.3v « tolèrent » ?

[Ttelmah]

Vddcore doesn't attach to anything except the capacitor. It is most definately
not 3.3v tolerant. 'Absolute maximum' rating is 2.5v.

[spilz]

But it should be connected to 3.3V to load the program through pickit, no ?

[spilz]

I soldered a new PIC
I disconnected 3.3v from Vcap
-> pic is not seen by pickit2

:(

[spilz]

Ok I think I found my mistake. I didn’t connect AVDD to 3.3V.
It seems to work now.

Thanks for your help.

Regards

[Ttelmah]

Yes. The note next to the minimum connection diagram, says: