R2023K datasheet(31/50 Pages) RICOH

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R2023K/T

Course (A)

When the time count precision of each RTC is not to be adjusted, the quartz crystal unit intended for use in that

RTC may have any CL value requiring no presetting.

The quartz crystal unit may be subject to frequency

variations which are selectable within the allowable range of time count precision.

Several quartz crystal units and

RTCs should be used to find the center frequency of the quartz crystal units by the method described in "P30

•

Measurement of Oscillation Frequency" and then calculate an appropriate oscillation adjustment value by the

method described in "P33

• Oscillation Adjustment Circuit" for writing this value to the R2023K/T.

Course (B)

When the time count precision of each RTC is to be adjusted within the oscillation frequency variations of the

quartz crystal unit plus the frequency variations of the real-time clock ICs, it becomes necessary to correct

deviations in the time count of each RTC by the method described in " P30

• Oscillation Adjustment Circuit".

Such oscillation adjustment provides quartz crystal units with a wider range of allowable settings of their oscillation

frequency variations and their CL values.

The real-time clock IC and the quartz crystal unit intended for use in

that real-time clock IC should be used to find the center frequency of the quartz crystal unit by the method

described in " P30

• Measurement of Oscillation Frequency" and then confirm the center frequency thus found to

fall within the range adjustable by the oscillation adjustment circuit before adjusting the oscillation frequency of the

oscillation circuit.

At normal temperature, the oscillation frequency of the oscillator circuit can be adjusted by up to

approximately

±0.5ppm.

Course (C)

Course (C) together with Course (D) requires adjusting the time count precision of each RTC as well as the

frequency of 32.768-kHz clock pulses output from the 32KOUT pin.

Normally, the oscillation frequency of the

crystal oscillator intended for use in the RTCs should be adjusted by adjusting the oscillation stabilizing capacitors

CG and CD connected to both ends of the crystal oscillator.

The R2023K/T, which incorporate the CG and the

CD, require adjusting the oscillation frequency of the crystal oscillator through its CL value.

Generally, the relationship between the CL value and the CG and CD values can be represented by the following

equation:

CL = (CG

× CD)/(CG + CD) + CS where "CS" represents the floating capacity of the printed circuit board.

The crystal oscillator intended for use in the R2023K/T is recommended to have the CL value on the order of 6 to

9pF.

Its oscillation frequency should be measured by the method described in " P.30

• Measurement of

Oscillation Frequency ".

Any crystal oscillator found to have an excessively high or low oscillation frequency

(causing a time count gain or loss, respectively) should be replaced with another one having a smaller and greater

CL value, respectively until another one having an optimum CL value is selected.

In this case, the bit settings

disabling the oscillation adjustment circuit (see " P.33

• Oscillation Adjustment Circuit") should be written to the

oscillation adjustment register.

Incidentally, the high oscillation frequency of the crystal oscillator can also be adjusted by adding an external

oscillation stabilization capacitor CGOUT or/and CDOUT as illustrated in the diagram below.

32kHz

OSCIN

OSCOUT

CGOUT

Oscillator

Circuit

CDOUT

*1) The CGOUT or/and CDOUT should have a

capacitance ranging from 0 to 6 pF.

R2023K Datasheet(PDF) 31 Page - RICOH electronics devices division

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