em3027 EM Microelectronic, em3027 Datasheet - Page 7
em3027
Manufacturer Part Number
em3027
Description
Real-time Clock With I2c Or Spi Interface, Crystal Temperature Compensation, Battery Switchover And Trickle Charger
Manufacturer
EM Microelectronic
Datasheet
1.EM3027.pdf
(27 pages)
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
em3027IDS
Manufacturer:
EM
Quantity:
20 000
Part Number:
em3027IDSSO8B+
Manufacturer:
EMMICRO
Quantity:
20 000
4.3
A frequency of the real crystal is dependent on the
temperature concurring with the following diagram:
T
F
Example 1: Qcoef=0.035; T
Copyright © 2008, EM Microelectronic-Marin SA
07/08 – rev B
O
O
-50
Δ F
F
– Turnover temperature in [°C]
– Crystal frequency when T
O
[ppm]
Crystal Thermal Behaviour
-200
-300
-400
-100
Figure 1 – Crystal thermal behaviour
0
-200
-400
-600
600
400
200
T
O
0
-100
R
0
[ppm]
T
O
-50
Temperature [°C]
O
50
O
Compensation Value
Crystal Error
=25; XtalOffset=–100
T
O
T
O
100
+50
Temperature
T
T [°C]
O
+100
150
The following formula expresses a compensation value
to be used during frequency correction.
Qcoef
T
T
XtalOffset
COMP_val
The Oscillator Frequency is adjusted, according to the
equation above by using coefficients located in the
EEPROM control page and a temperature.
The actual temperature can be obtained from the internal
thermometer or from Temp register updated externally by
an application.
A principle of the frequency compensation is based on
the adding/removing of pulses.
Example 2: Qcoef=0.035; T
7
-50
O
COMP_val
-100
-200
-300
-400
400
300
200
100
0
0
=
– Thermal quadratic coefficient [ppm/°C
– Actual temperature in [°C]
– Turnover temperature in [°C]
– Crystal offset at T
– Compensation value result in [ppm]
[ppm]
Qcoef
×
(T
50
O
Compensation Value
Crystal Error
=25; XtalOffset=+100
−
To)
www.emmicroelectronic.com
O
EM3027
2
[ppm]
−
XtalOffset
100
Temperature
2
]
150