MPC9229 REVISION 5 DECEMBER 19, 2012

9

©2012 Integrated Device Technology, Inc.

MPC9229 Data Sheet

400MHZ LOW VOLTAGE PECL CLOCK SYNTHESIZER

Figure 5. PCB Board Layout Recommendation

for the PLCC28 Package

Using the On-Board Crystal Oscillator

The MPC9229 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 MPC9229 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. For crystals with a higher shunt

capacitance, it may be required to place a resistance across the

terminals to suppress the third harmonic. Although typically not

required, it is a good idea to layout the PCB with the provision of

adding this external resistor. The resistor value will typically be

between 500 and 1 K

.

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 MPC9229 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 11. below specifies the performance

requirements of the crystals to be used with the MPC9229.

1

C2

CF

XTAL

C1

C1

R1 = 10–15



C1 = 0.01

F

C2 = 22

F

C3 = 0.01

F

= VCC

= GND

= Via

Table 11. Recommended Crystal Specifications

Parameter

Value

Crystal Cut

Fundamental AT Cut

Resonance

Series Resonance(1)

1. Refer to the accompanying text for series versus parallel resonant

discussion.

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 – 7pF

Equivalent Series Resistance (ESR)

50 to 80



Correlation Drive Level

100

W

Aging

5 ppm/Yr (First 3 Years)