RV5C338A-E2 Просмотр технического описания (PDF) - RICOH Co.,Ltd.

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RV5C338A-E2

3-WIRE SERIAL INTERFACE REAL-TIME CLOCK ICS WITH VOLTAGE MONITORING FUNCTION

RICOH Co.,Ltd. 

R×5C338A

2.2 Measurement of Oscillation Frequency

R×5C338A

VDD

OSCIN

OSCOUT

CLKC

32KOUT

VSS

32.768kHz

Frequency

counter

*1) The R×5C338A are configured to generate 32.768-kHz clock pulses for output from the 32KOUT pin at power-on conditionally on setting the XSTP bit

to 1 in the control register 2.

*2) A frequency counter with 6 (more preferably 7) or more digits on the order of 1ppm is recommended for use in the measurement of the oscillation fre-

quency of the oscillation circuit.

*3) The CLKC input should be connected to the VDD pin with a pull-up resistor.

2.3 Adjustment of Oscillation Frequency

The oscillation frequency of the oscillation circuit can be adjusted by varying procedures depending on the usage of

the R×5C338A in the system into which they are to be built and on the allowable degree of time count errors. The

flow chart below serves as a guide to selecting an optimum oscillation frequency adjustment procedure for the

relevant system.

Start

Use 32-kHz NO

clock circuit?

YES

Allowable time count precision is on order of oscillation

frequency variations of crystal oscillator *1 plus

frequency variations of real-time clock? *2, *3

YES

Use 32-kHz clock circuit without regard

to its frequency precision?

NO

Allowable time count precision is on order of oscillation

frequency variations of crystal oscillator *1 plus

frequency variations of real-time clock? *2, *3

YES

NO

YES

NO

To Course (A)

To Course (B)

To Course (C)

To Course (D)

*1) Generally, crystal oscillators for commercial use are classified in terms of their center frequency depending on their load capacitance (CL) and further

divided into ranks on the order of ±10, ± 20, and ±50 ppm depending on the degree of their oscillation frequency variations.

*2) Basically, the R×5C338A are configured to cause frequency variations on the order of ±5 to ±10ppm at normal temperature.

*3) Time count precision as referred to in the above flow chart is applicable to normal temperature and actually affected by the temperature characteristics

and other properties of crystal oscillators.

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