HT1382_1105 HOLTEK [Holtek Semiconductor Inc], HT1382_1105 Datasheet - Page 10

• Manufacturer Part Number: HT1382_1105
• Description: I2C/3-Wire Real Time Clock
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

HT1382
2
I
C/3-Wire Real Time Clock
Clock Compensation
The device includes a digital trimming method for clock error correction due to temperature variations
of the crystal oscillator. This can be implemented as manufacturing calibration or user active
calibration. The crystal accuracy to temperature characteristic is similar to that shown in the diagram.
The Digital Trimming Register, DT, is used for clock compensation. Correction is performed once
every 10 seconds or 30 seconds. The minimum resolution is 3.052ppm or 1.017ppm and the device has
a correction in the range of 192.276ppm or 64.071ppm.
Set FO3~FO0= 1010 , the FOUT pin will have 1Hz clock pulse output. Measure the FOUT
frequency using a high-accuracy frequency counter with 7 or more digits. The correction value is
calculated using the formula shown below.
1Hz - (measured value)
Correction value = integral value
(
)
minimum resolution (3.052ppm or 1.014ppm)
When clock compensation is used, set FO3~FO0= 1010 , and the FOUT pin will have 1Hz clock
pulse output. The cycle changes once in 10 seconds or in 30 seconds as shown below. In the diagram
a denotes a non-correctional cycle, and b denotes a correctional cycle. Measure a and b using a
high-accuracy frequency counter of 7 or more digits. Calculate the average frequency based on the
measured result.
For DTS = 0, the average period = (a 9 + b) 10
For DTS = 1, the average period = (a 29 + b) 30
Rev. 1.40
10
May 27, 2011