Crystal oscillator in SLG46533V

⚠️
Hi there.. thanks for coming to the forums. Exciting news! we’re now in the process of moving to our new forum platform that will offer better functionality and is contained within the main Dialog website. All posts and accounts have been migrated. We’re now accepting traffic on the new forum only - please POST any new threads at https://www.dialog-semiconductor.com/support . We’ll be fixing bugs / optimising the searching and tagging over the coming days.
5 posts / 0 new
Last post
dbvanhorn
Offline
Last seen: 3 years 3 months ago
Joined: 2019-05-25 21:23
Crystal oscillator in SLG46533V

I'm having no luck with the crystal oscillator block.

My crystal is custom made, 14.7 MHz.  I applied the 15pF caps from pins 16 1nd 17 to ground, and the 500 ohm feedback resistor.

Oscillator is enabled, with no matrix PD.  The oscillator "PWR UP" pin in designer refuses to connect to Gnd, VCC, or POR, so I assume that is not needed.

Both lines just sit quietly at 1.5V. 

There is no short between pins 16 and 17, I read 500 ohms

Since attaching the crystal, I also get functional socket test fails on pins 4, 6, 8, 9, 12, 15, 18, 19, 20.  The last four are not even used in my design.

Pin 4 is a digital output, Pin 6 and 12 also, pins 8 and 9 are the I2C block,

The physical implementation is a 20 pin board with the device on it, plugged into the DIP development platform.  No pins from there are connected to anything else.

Device: 
Device Number: 
SLG46533V
dbvanhorn
Offline
Last seen: 3 years 3 months ago
Joined: 2019-05-25 21:23
We found the problem.   First

We found the problem.   First, the online help is wrong about the resistor value.  500 ohms is not correct, the chip data sheet says 1M for my frequency range.

Second, even with the resistor changed, the oscillator didn't work.  This was caused by electronics on the  DIP development board loading down those pins.   The workaround was simply to clip off the two crystal pins #16 and #17 so they don't connect to the DIP development board anymore.   This causes some errors when loading, "Functional Socket Test Failed" but this error can be skipped.

Once we discovered all that, things went MUCH better, and I was able to weed out the few errors in my project logic very quickly.

Some of the logic events in my project take 12 hours to happen in real time, so getting out of simulation was pretty crucial.

 

pavloZ
Offline
Last seen: 2 years 6 months ago
Staff
Joined: 2018-01-31 12:50
Hi David,

Hi David,

thanks for your question it helps us to find obsolete information in the designer's help.

Please refer to the base datasheet https://www.dialog-semiconductor.com/sites/default/files/slg46533r119_11...

section 16.0 (see attached)

The resistance should be 1MOhm not 500 OHm for successfull run. That's why the functional socket test fails during debug also.

Attachment: 
dbvanhorn
Offline
Last seen: 3 years 3 months ago
Joined: 2019-05-25 21:23
We had to clip pins 16 and 17

We had to clip pins 16 and 17 so that the oscillator could work while plugged into the DIP dev board.

We now find that we can't program the chip, are pins 16 and 17 used in chip programming?

pavloZ
Offline
Last seen: 2 years 6 months ago
Staff
Joined: 2018-01-31 12:50
Yes you are right, pin 16

Yes you are right, pin 16(IO13) is "programming mode control" and used for programming.