Rainbow-electronics MAX3627 Manual do Utilizador descarregar pdf (Página 10)

MAX3627

+3.3V, Low-Jitter, Precision Clock

Generator with Multiple Outputs

10 ______________________________________________________________________________________

Table 1. Crystal Selection Parameters

The layout shown in Figure 5 gives approximately 2pF

of trace plus footprint capacitance per side of the crys-

tal (Y1). The dielectric material is FR4, and dielectric

thickness of the reference board is 15 mils. Using a

25MHz crystal and the capacitor values of C45 = 27pF

and C46 = 33pF, the measured output frequency accu-

racy is -1ppm at +25°C ambient temperature.

Crystal Selection

The crystal oscillator is designed to drive a fundamental

mode, AT-cut crystal resonator. See Table 1 for recom-

mended crystal specifications. See Figure 6 for external

capacitance connection.

Figure 5. Crystal Layout

X_IN

X_OUT

27pF

33pF

CRYSTAL

= 18pF)

MAX3627

Figure 6. Crystal, Capacitors Connection

PARAMETER SYMBOL MIN TYP MAX UNITS

Crystal Oscillation Frequency f

OSC

25 MHz

Shunt Capacitance C

7.0 pF

Load Capacitance C

18 pF

Equivalent Series Resistance (ESR) R

50 

Maximum Crystal Drive Level 300 μW

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Rainbow-electronics MAX3627 Manual do Utilizador Página 10