RV-3029 Datasheet, PDF (38/67 Pages) MICORO CRYSTAL SWITZERLAND – DTCXO Temperature Compensated Real Time Clock

Micro Crystal
DTCXO Temperature Compensated Real Time Clock / Calendar Module
RV-3029
5.2. COMPENSATION PRINCIPLE
The Frequency Compensation Unit “FCU” is calculating every 32 seconds a Frequency Compensation Value
based on individual device data:
• XTAL offset:
Device individual frequency deviation ±20ppm @ 25°C
• XTAL T₀:
Xtal’s turnover temperature 25°C ±5°C
• XTAL temp. coefficient: Xtal’s frequency drift vs. temperature -0.035 ppm * (T-T₀)² ±10%
• Temperature:
Measured ambient temperature
Calculating the Anticipated Frequency Deviation and the Time Compensation Value
400
350
Calculated Time
Compensation Value
300
250
200
150
100
50
XTAL OFFSET
∆f/f = +/-20 ppm
0
-50
-100
-150
XTAL T₀
T₀ = 25°C (+/-5°C)
-200
-250
-300
XTAL Temperature Coefficient
∆f/f [ppm] = -0.035 * (T_amb-T₀)² (+/-10%)
-350
-400
-50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140
Temperature [°C]
Note:
The 32.768 kHz frequency is adjusted according to the calculated Time Compensation value.
The compensation itself is achieved by adding or subtracting clock-pulses to the 32.768 kHz reference clock.
One complete compensation period takes 32 seconds.
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