L M X 2 5 3 1 L Q 1 2 2 6 E E V A L U A T I O N B O A R D O P E R A T I N G I N S T R U C T I O N S
Loop Filter
Loop Bandwidth
8.0 kHz
K
φ
1440 uA (16X)
Phase Margin
61.3 deg
Fcomp
10 MHz
Crystal Frequency
10 MHz
Output Frequency
1184 – 1268 MHz (DIV2=0)
592 - 634 MHz (DIV2=1)
Supply Voltage
3.0 Volts
VCO Gain
3 - 6 MHz/Volt
VCO
CPout
op
en
100 nF
1K
Ω
100 pF
100 pF
20 K
Ω
20 K
Ω
Vtune
Quick Setup
•
Install the CodeLoader software which is available at
www.national.com/timing
.
•
Attach the parallel , or USB to parallel, port cable to the computer and the evaluation board.
•
Connect 3.0 volts to the
Vcc
connector
•
Connect the
Fout
connector to a spectrum analyzer or phase noise analyzer
•
Connect a clean 10 MHz source to the
OSCin
pin. Typically, the 10 MHz output from the back
of the RF test equipment is a good source. Signal generators tend to be very noisy and should
be used with caution. If a signal generator is used, the signal generator phase noise
contribution can be reduced by setting the signal to 80 MHz and dividing this down to a phase
detector frequency of 10 MHz.
•
Set up the CodeLoader software
o
Select the proper part from the menu as Select Part->PLL+VCO->LMX2531LQ1226E
o
Select the proper mode from the Mode menu
o
Load the part by pressing Ctrl+L or selecting Keyboard Controls->Load Device from
the menu
•
It is recommended to ensure proper communication with the device
o
Click the REG_RST bit on the bits/pins page and observe the current go to 0 mA
o
Unclick the REG_RST bit AND press Ctrl+L. The current should be approximately
35 mA
o
If device does not respond to this, consult the troubleshooting section
•
When using the lower frequency band with divide by 2 enabled (DIV2=1), be aware that the
frequency programmed to the VCO is actually twice the output frequency of the device
because the VCO frequency is being divided by 2.
3
