RTC works sometimes (LPC1764 board)

[lpcware]

Content originally posted in LPCWare by Luis Digital on Thu Aug 09 15:50:35 MST 2012
Hello,

The RTC clock works when I touch with a wire pin 18 (output from the RTC oscillator circuit), otherwise it will not oscillate.

Any ideas?

Thank you.

[lpcware]

Content originally posted in LPCWare by Luis Digital on Fri Aug 10 11:56:33 MST 2012
I was watching a crystal mounted in a PC motherboard, and I noticed it had a 10M resistor in parallel, I added and now my runs.

I thought the microcontroller had one in the oscillator.

Thanks Zero for your help.

[lpcware]

Content originally posted in LPCWare by Luis Digital on Fri Aug 10 08:40:04 MST 2012
Yes, I read that document, and tried with 0 ohms.

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Fri Aug 10 06:47:59 MST 2012
High ESR :mad: = Low Loop gain :o

Did you try to increase your gain?

See chapter 7: Insufficient Loop Gain of

'Crystal Oscillator Troubleshooting Guide' (Freescale :eek:)

http://cache.freescale.com/files/microcontrollers/doc/app_note/AN3208.pdf?fsrch=1&sr=1

[lpcware]

Content originally posted in LPCWare by Luis Digital on Fri Aug 10 06:04:58 MST 2012
Crystal: SSP-T6-7PF-20PPM (7pF)

I am using:
Load Cap.: 5pF
100K resistor

Thank you.

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Fri Aug 10 00:18:04 MST 2012

---

Quote: Luis Digital
Is not it obvious?
 

---

Somehow I've overseen the description of your schematic :confused:

So which crystal did you add (Load capacitance), which caps did you use and did you add a resistor to isolate the output impedance of your LPC :confused:

[lpcware]

Content originally posted in LPCWare by Luis Digital on Thu Aug 09 19:31:57 MST 2012

---

Quote: Zero
Add a crystal ?

---

Is not it obvious?
 
Maybe the crystal is damaged, a problem with the capacitors, I do not know (that's why I asked lol).

I am doing more tests.

[lpcware]

Content originally posted in LPCWare by Ex-Zero on Thu Aug 09 17:20:06 MST 2012
Add a crystal ?