Datasheet

LMX2531LQ1146E EVALUATION BOARD OPERATING INSTRUCTIONS
Loop Filter
Loop Bandwidth
7.9
Kφ
1440 uA (16X)
Phase Margin
61.4
Fcomp
10 MHz
Crystal Frequency
10 MHz
Output Frequency
1106 - 1184 MHz (DIV2=0)
553 - 592 MHz (DIV2=1)
Supply Voltage
3.0 Volts
VCO Gain
2.5-5.5 MHz/Volt
VCO
CPout
open
100 nF
1KΩ
100 pF 100 pF
20 KΩ 20 KΩ
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->LMX2531LQ1146E
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