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CERAMIC RESONATOR PRINCIPLES - page 6 / 7

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CERAMIC RESONATOR APPLICATIONS

OSCILLATION RISE TIME

Oscillation rise time means the time when oscillation develops from a transient area to a steady area at the time the power to the IC is activated. With a ceramic resonator, it is defined as the time to reach 90% of the oscillation level under steady conditions as shown in Fig.6.1.

Rise time is primarily a function of oscillating circuit design. Generally, smaller loading capacitance, a higher frequency ceramic resonator, and a smaller size of ceramic resonator will cause a faster rise time. The effect of load capacitance becomes more apparent as the capacitance of the resonator decreases. Fig.6.2 shows an actual measurement of rise time

against load capacitance (CL) and supply voltage. It is noteworthy that the rise time is one or two decades faster for a ceramic resonator than for a quartz crystal. (This point is graphically illustrated in Fig. 6.3)

Starting Voltage: Starting voltage means the minimum supply voltage at which an oscillating circuit can operate. Starting voltage is affected by all circuit elements. It is determined mostly by the characteristics of the IC. Fig.6.4 shows an example of an actual measurement for the starting voltage characteristics against the loading capacitance.

ON

10

VDD

5

OV

2

IC: TC74HCU04P VDD = +5.OV CL1 = CL2 = 100PF

Crystal

1

0.9 x Vp-p

Vp-p

Rise Time (msec)

0.5

0.2

0.1

Ceramic

t=0

Rise Time

Time

0.05

Figure 6.1) Definition of Rise Time

0.02

0.01

Oscillation Rise Time (ms)

1.0

0.5

(IC: CD4069UBE, Resonator: ZTA4.0MG)

0

0.5

1.0

2.0

5.0

10

20

Oscillation Frequency (MHz)

Figure 6.3) Rise Time vs. Oscillation Frequency for both Ceramic and Crystal Resonators

0

0

2

5

8

Supply Voltage (V)

(a) Supply Voltage Characteristics

Oscillation Rise Time (ms)

1.0

0.5

0

0

(IC: CD4069UBE, Ceramic Resonator: ZTA4.0MG)

20

40

60

80 100 Supply Voltage (V)

Starting Voltage (V)

+5

+4

+3

+2

+1 0

(IC: CD4069UBE, Resonator: ZTA4.0MG)

  • 0

    20

40

60

80

C 100 L ( p F )

( b ) C L C h a r a c t e r i s t i c s ( C L = C

L2

)

Figure 6.2) Example of Actual Measurements for the Charac. of Oscillation Rise Time

Figure 6.4) Starting Voltage Characteristics Against CL (CL1 = CL2)

ECS, INC. INTERNATIONAL 1105 S. RIDGEVIEW, OLATHE, KS 66062 • 913-782-7787 • 800-237-1041 • FAX 913-782-6991 • WWW.ECSXTAL.COM

TECHNICAL REFERENCE

93

TECHNICAL REFERENCE

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