ICS1893BK datasheet(28/133 Pages) ICST

28 / 133 page

ICS1893BF, Rev. C, 9/29/05

September, 2005

Chapter 5 Interface Overviews

ICS1893BF Data Sheet - Release

If a crystal is used as the clocking source, connect it to both the Ref_in (pin 47) and Ref_out (pin 46) pins

of the ICS1893BF. A pair of bypass capacitors on either side of the crystal are connected to ground. The

crystal is used in the parallel resonance or anti-resonance mode. The value of the bypass caps serve to

adjust the final frequency of the crystal oscillation. Typical applications would use 33pF bypass caps. The

exact value will be affected by the board routing capacitance on Ref_in and Ref_out pins. Smaller bypass

capacitors raise the frequency of oscillation. Once the exact value of bypass capacitance is established it

will be the same for all boards using the same specification crystal. The best way to measure the crystal

frequency is to measure the frequency of TXCLK (pin 37) using a frequency counter with a 10 second

sample. Using TXCLK prevents affecting the crystal frequency by the measurement. The crystal

specification is shown in Table 5.1.

Table 5-1. 25MHz Crystal Specification

Specifications

Symbol Minimum

Typical Maximum

Unit

Fundamental Frequency

(tolerance is sum of freq.,

temp., stability and aging.)

24.99875 25.00000

25.00125

MHz

Freq. Tolerance

∆F/f

± 50

ppm

Input Capacitance

Cin

Table 5-2. 25MHz Oscillator Specification

Specifications

Symbol Minimum

Typical Maximum

Unit

Output Frequency

24.99875 25.00000

25.00125

MHz

Freq. Stability (including aging)

∆F/f

± 50

ppm

Duty cycle CMOS level

one-half VDD

Tw/T

VIH

2.79

Volts

VIL

0.33

Volts

Period Jitter

Tjitter

500

Input Capacitance

CIN

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