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MK2049-34A

3.3 Volt Communications Clock VCXO PLL

Integrated Circuit Systems 

MK2049-34A

3.3 Volt Communications Clock VCXO PLL

External Component Selection

The MK2049-34A requires a minimum number of external components for proper operation. Decoupling capacitors

of 0.01µF must be connected between VDD and GND pins close to the chip (especially pins 4 and 7, 15 and 17),

and 33Ω series terminating resistors should be used on clock outputs with traces longer than one inch (assuming

50Ω traces). The selection of additional external components is described in the following sections.

Loop Filter

Information on how to configure the external loop filter, connected between pins CAP1 and CAP2, can be found at

http://www.icst.com/products/telecom/telecom.htm and http://www.icst.com/PDF/MK2049-3x%20Addendum.pdf.

Crystal Operation

The MK2049-34A operates by phase locking the input signal to a VCXO which consists of the recommended

pullable VCXO crystals and the integrated VCXO oscillator circuit on the MK2049-34A. To achieve the best

performance and reliability, the layout guidelines shown on the previous page should be closely followed.

The frequency of oscillation of a quartz crystal is determined by its cut and by the load capacitors connected to it.

The MK2049-34A has variable load capacitors on-chip which “pull” or change the frequency of the crystal. External

stray capacitance must be kept to a minimum to ensure maximum pullability of the crystal. To achieve this, the

layout should use short traces between the MK2049-34A and the crystal.

For the VCXO to operate correctly, a pullable crystal must be used. For more information, including a list of

approved crystals, please refer to application note MAN05 (http://www.icst.com/products/summary/man05.htm).

Absolute Maximum Ratings

Stresses above the ratings listed below can cause permanent damage to the MK2049-34A. These ratings,

which are standard values for ICS commercially rated parts, are stress ratings only. Functional operation of

the device at these or any other conditions above those indicated in the operational sections of the

specifications is not implied. Exposure to absolute maximum rating conditions for extended periods can

affect product reliability. Electrical parameters are guaranteed only over the recommended operating

temperature range.

Item

Supply Voltage, VDD

All Inputs and Outputs

Ambient Operating Temperature

Storage Temperature

Junction Temperature

Soldering Temperature

Rating

7V

-0.5 V to VDD+0.5 V

-40 to +85°C

-65 to +150°C

175°C

250°C

MDS 2049-34A A

6

Revision 032504

Integrated Circuit Systems, Inc. z 525 Race Street, San Jose, CA 95126 z tel (408) 297-1201 z www.icst.com

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