QS W5200 RTC drift
oodes
Posts: 131
in Accessories
Hello,
I'm using the w5200 for QS and my RTC is experiencing some significant time drifts, is it possible to calibrate the rtc on the w5200? The rtc is running fast up to about 15 seconds per day at room temperature ~20 Deg C. From looking at the seiko S-35390A datasheet if anything temperature effects should have a slowing down effect on the rtc , but in my case it speeding up.
"Caution 1. The oscillation frequency varies depending on the ambient temperature and power supply
voltage. Refer to " Characteristics (Typical Data)".
2. The 32.768 kHz crystal oscillator operates more slowly at an operating temperature higher or
lower than +20°C to +25°C. Therefore, it is recommended to set the oscillator to operate
slightly faster at normal temperature
Do i need to adjust the capacitor values on the board , which would involve desoldering and soldering to correct this as its quite a drift?
I'm using the w5200 for QS and my RTC is experiencing some significant time drifts, is it possible to calibrate the rtc on the w5200? The rtc is running fast up to about 15 seconds per day at room temperature ~20 Deg C. From looking at the seiko S-35390A datasheet if anything temperature effects should have a slowing down effect on the rtc , but in my case it speeding up.
"Caution 1. The oscillation frequency varies depending on the ambient temperature and power supply
voltage. Refer to " Characteristics (Typical Data)".
2. The 32.768 kHz crystal oscillator operates more slowly at an operating temperature higher or
lower than +20°C to +25°C. Therefore, it is recommended to set the oscillator to operate
slightly faster at normal temperature
Do i need to adjust the capacitor values on the board , which would involve desoldering and soldering to correct this as its quite a drift?
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Thanks for the heads up on the DS3231 modules also
That's around 174ppm, which sounds high.
How many units have you checked, and did the original designer properly select the capacitors for the xtal used ?
That's a question for Parallax as its their board
I'm just looking now at the clock correction function for the S-35390A, I should be able to use that to correct the clock?
Certainly someone in Parallax should check this, if all units are skewed one way, do you have accurate numbers on all units tested ?
Even the cheapest Crystals should be ±20ppm at room temp, but they do have to be correctly load-cap matched.
The recommended crystal characteristic values are, C L value (load capacitance) = 6 pF, R 1 value (equivalent serial resistance) = 50 k Ω max.
Yes, but the skew you quote is pushed to almost the trim limit.
I'm just testing them again with adjusted clock correction value which appears to be working so far but yes I do agree its an excessive amount of drift.
I know with the provided code available for download with the W5200 units the real-time clocks are synced via SNTP which is fine if your using an Internet connection and this is why I probably didnt notice it before.