V62SLASH12615-01XE-R datasheet(59/92 Pages) TI1

59 / 92 page

DP83848-EP

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SLLSEC6D – SEPTEMBER 2012 – REVISED JUNE 2013

7.3.2

Crystal

A 25 MHz, parallel, 20 pF load crystal resonator should be used if a crystal source is desired. Figure 7-2

shows a typical connection for a crystal resonator circuit. The load capacitor values will vary with the

crystal vendors; check with the vendor for the recommended loads.

The oscillator circuit is designed to drive a parallel resonance at cut crystal with a minimum drive level of

100

μW and a maximum of 500 μW. If a crystal is specified for a lower drive level, a current limiting

resistor should be placed in series between X2 and the crystal.

As a starting point for evaluating an oscillator circuit, if the requirements for the crystal are not known, CL1

and CL2 should be set at 33 pF, and R1 should be set at 0

Ω.

Specification for 25 MHz crystal are listed in Table 7-3.

Figure 7-2. Crystal Oscillator Circuit

Table 7-1. 25 MHz Oscillator Specification

PARAMETER

MIN

TYP

MAX

UNIT

CONDITION

Frequency

MHz

Frequency tolerance

±50

ppm

Operational temperature

Frequency stability

±50

ppm

1 year aging

Rise/Fall time

20% - 80%

Jitter

800(1)

Short term

Jitter

800(1)

Long term

Symmetry

40%

60%

Duty cycle

(1)

This limit is provided as a guideline for component selection and to guaranteed by production testing. Refer to AN-1548, “PHYTER 100

Base-TX Reference Clock Jitter Tolerance,“ for details on jitter performance.

Table 7-2. 50 MHz Oscillator Specification

PARAMETER

MIN

TYP

MAX

UNIT

CONDITION

Frequency

MHz

Frequency tolerance

±50

ppm

Operational temperature

Frequency stability

±50

ppm

Operational temperature

Rise/Fall time

20% - 80%

Jitter

800(1)

Short term

Jitter

800(1)

Long term

Symmetry

40%

60%

Duty cycle

(1)

This limit is provided as a guideline for component selection and to guaranteed by production testing. Refer to AN-1548, “PHYTER 100

Base-TX Reference Clock Jitter Tolerance,“ for details on jitter performance.

DESIGN GUIDELINES

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