lmx2337 National Semiconductor Corporation, lmx2337 Datasheet - Page 12

• Manufacturer Part Number: lmx2337
• Description: Pllatinum? Dual Frequency Synthesizer For Rf Personal Communications
• Manufacturer: National Semiconductor Corporation

www.national.com
Typical Application Example
Operational Notes:
Application Hints:
Proper use of grounds and bypass capacitors is essential to achieve a high level of performance. Crosstalk between pins can be reduced by careful board
layout.
This is an electrostatic sensitive device. It should be handled only at static free work stations.
Application Information
A block diagram of the basic phase locked loop is shown in Figure 1 .
*
**
***
****
VCO is assumed AC coupled.
R
200
50
CMOS clock is used and no terminating resistor is required. OSC
mended because the input circuit provides its own bias. (See Figure below).
Adding RC filters to the V
IN
increases impedance so that VCO output power is provided to the load rather than the PLL. Typical values are 10 to
termination is often used on test boards to allow use of external reference oscillator. For most typical products a
depending on the VCO power level. f
CC
lines is recommended to reduce loop-to-loop noise coupling.
FIGURE 1. Conventional PLL Architecture
IN
RF impedance ranges from 40
12
in
DS012332-11
may be AC or DC coupled. AC coupling is recom-
to 100 . f
IN
IF impedances are higher.
DS012332-12
DS012332-10