Philips Semiconductors

Product data

PCK12429

25–400 MHz differential PECL clock generator

2002 Jun 03

8

SYMBOL

PARAMETER

TEST CONDITIONS

LIMITS

UNIT

MIN

MAX

F

Maximum Input Frequency

S_CLOCK

Note 1

—

10

MHz

Maximum Input Frequency

Xtal Oscillator

Note 1

10

20

MHz

F

O

Maximum Output Frequency

VCO (Internal)

Note 2

200

400

MHz

Maximum Output Frequency

Note 2

25

400

MHz

Maximum PLL Lock Time

—

10

ms

RMS jitter (peak-to-peak)

Note 2

See Applications Section

—

±25

ps

S_DATA to

S_CLOCK

20

—

Setup Time

S_CLOCK TO

S_LOAD

20

—

ns

M, N to P_LOAD

20

—

Hold Time

S_DATA to

S_CLOCK

20

—

ns

n

M, N to P_LOAD

20

—

tpw

Minimum Pulse Width

S_LOAD

Note 2

50

—

ns

Minimum Pulse Width

P_LOAD

Note 2

50

—

ns

Output Rise/Fall

20%–80%, Note 2

100

400

ps

Duty Cycle

45

55

%

NOTES:

1. 10 MHz is the maximum frequency to load the feedback device registers. S_CLOCK can be switched at higher frequencies when used as a

test clock in TEST_MODE 6. Crystal frequency of 16MHz verified at productiontest. 10 to 20MHz operationguaranteed by design.

2. 50

APPLICATIONS INFORMATION

Using the on-board crystal oscillator

The PCK12429 features a fully integrated on-board crystal oscillator

to minimize system implementation costs. The oscillator is a series

resonant, multivibrator type design as opposed to the more common

parallel resonant oscillator design. The series resonant design

provides better stability and eliminates the need for large on chip

capacitors. The oscillator is totally self contained so that the only

external component required is the crystal. As the oscillator is

somewhat sensitive to loading on its inputs, the user is advised to

mount the crystal as close to the PCK12429 as possible to avoid

any board level parasitics. To facilitate co-location surface mount

crystals are recommended, but not required. Because the series

resonant design is affected by capacitive loading on the XTAL

terminals, loading variation introduced by crystals from different

vendors could be a potential issue.

The oscillator circuit is a series resonant circuit and thus for

optimum performance a series resonant crystal should be used.

Unfortunately most crystals are characterized in a parallel resonant

mode. Fortunately there is no physical difference between a series

resonant and a parallel resonant crystal. The difference is purely in

the way the devices are characterized. As a result, a parallel

resonant crystal can be used with the PCK12429 with only a minor

error in the desired frequency. A parallel resonant mode crystal used

in a series resonant circuit will exhibit a frequency of oscillation a

few hundred ppm lower than specified, a few hundred ppm

translates to kHz inaccuracies. In a general computer application

this level of inaccuracy is immaterial. Table 2 specifies the

performance requirements of the crystals to be used with the

PCK12429.

Table 2. Test modes

PARAMETER

VALUE

Crystal Cut

Fundamental AT Cut

Resonance

Series Resonance*

Frequency Tolerance

±75 ppm at 25 °C

Frequency/Temperature Stability

±150 pm 0 to 70 °C

Operating Range

0 to 70

°C

Shunt Capacitance

5–7 pF

Equivalent Series Resistance (ESR)

50 to 80

Ω

Correlation Drive Level

100

µW

Aging

5 ppm/Yr (first 3 years)

NOTE:

*

See accompanying text for series versus parallel resonant

discussion.