Datasheet

LMX2531LQ2820E EVALUATION BOARD OPERATING INSTRUCTIONS
Loop Filter
Loop Bandwidth
14 kHz
Kφ
1440 uA (16X)
Phase Margin
54.1 °
F
PD
10 MHz
Crystal Frequency
10 MHz
Output Frequency
2710 to 2925 MHz (DIV2=0)
1355 to 1462 MHz (DIV2=1)
Supply Voltage
3.0 Volts
VCO Gain
12 to 28 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/software/.
• Attach the parallel cable or USB <--> uWire 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 OS Cin 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->LMX2531LQ2820E
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.
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