R

V3021

Copyright © 2005, EM Microelectronic-Marin SA

4

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The V3021 will run slightly too fast, in order to allow the

user to adjust the frequency, depending on the mean

operating temperature. This is made since the crystal

adjustment can only work by lowering the frequency with

circuit

capacitance

has

also

to

be

taken

into

consideration. The V3021 in DIL 8 package, running with

an 8.2 pF crystal at room temperature, will be adjusted to

better

than

±1s/day

with

a

6.8

pF

capacitor.

Typical Frequency on I/O Pin

Typical drift for ideal 32'768 Hz quartz

Note

: The trimming capacitor value must not exceed

15 pF. Greater values may disturb the oscillator

function

Fig. 3

Quartz Characteristics

O

F

F

∆

= -0.038

2

C

ppm

°

=

the ratio of the change in frequency to the

nominal value expressed in ppm (it can be

thought of as the frequency deviation at any

temperature)

T

=

the temperature of interest in °C

=

the turnover temperature (25 ± 5°C)

To determine the clock error (accuracy) at a given

temperature, add the frequency tolerance at 25°C to the

value obtained from the formula above.

Fig. 4