Electronics > Microcontrollers

DS3231 intermittent start-up issues when coin-cell battery connected

(1/5) > >>

newtekuser:
I have a DS3231MZ connected to a PIC as per the attached diagram. If the coin cell battery is present it frequently causes the IC to misbehave on power-on where it just hangs (when debugging I see it hangs during i2c start)
This does not happen on power-on if the battery is not present. How does the presence of the battery affect it and what can I do to solve this?

iMo:
There is an internal comparator which compares Vpf (power fail) voltage of aprox 2.6V (internal reference) and asserts reset (see the DS).
It could happen this somehow triggers. For example your battery is low, your Vcc is low, add decoupling capacitors (your 10nF is too low, go with 10u for example), etc..

selcuk:
I used DS3231SN with two 100nF capacitors, one at Vbat and the other on at Vcc. I haven't noticed this issue. Vcc is 3.3V. They are similar chips. I can recommend using at least the minimum capacitances written on the datasheet.

hugo:
To improve things you could try using stronger pull-up resistors (3k3, 4k7) and a decoupling capacitor of 1uF.

newtekuser:

--- Quote from: hugo on June 16, 2024, 04:53:21 pm ---To improve things you could try using stronger pull-up resistors (3k3, 4k7) and a decoupling capacitor of 1uF.

--- End quote ---

I am using 10K resistors on SDA and SCL lines and also swapped the cap for 100nF on Vcc but it didn't make a difference.

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod