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• This catalog has only typical specifications because there is no space for detailed specifications. Therefore, please review our product specifications or consult the approval sheet for product specifications before ordering.

5

3. Characteristics of Oscillation Rise Time

Oscillation rise time means the time when oscillation

develops from a transient area to a steady state

condition, at the time the power of the IC is activated.

reach 90% of the oscillation level under steady state

conditions as shown in Fig. 5-3.

Rise time is primarily a function of the oscillation circuit

design. Generally, smaller loading capacitance, higher

frequency of ceramic resonator, and lower mechanical Q

of ceramic resonator cause a faster rise time. The effect

of load capacitance becomes more apparent as the

capacitance of the resonator decreases.

Fig. 5-4 shows how the rise time increases as the load

capacitance of the resonator increases. Also, Fig. 5-4

shows how the rise time varies with supply voltage.

It is noteworthy that the rise time of the ceramic

resistor is one or two decades faster than a quartz

crystal.

Fig. 5-5 shows comparison of rise time between the two.

Fig. 5-3 Definition of Rise Time

t=0

0.9ⅹVp-p

0V

ON

Vp-p

Rise Time

Time

Fig. 5-4 Examples of Characteristics of Oscillation Rise Time

(IC: TC74HCU04 (TOSHIBA),

Supply Voltage Characteristics

2

0

0.50

1.00

468

0

0

0.50

1.00

110

100

Fig. 5-5 Comparison of the Rise Time of

a Ceramic Resonator vs. a Quartz Crystal

CRYSTAL

(33.868MHz)

CSACW33M8X51–B0

IC : TC74HCU04AP(TOSHIBA)

↑ 2.0V/div.

→0.1msec./div.

P17E.pdf

2012.10.31