LMX2485E EVAL National Semiconductor, LMX2485E EVAL Datasheet - Page 3

• Manufacturer Part Number: LMX2485E EVAL
• Description: BOARD EVALUATION LMX2485E
• Manufacturer: National Semiconductor
• Series: PLLatinum™r

Specifications of LMX2485E EVAL

• Main Purpose: Timing, Frequency Synthesizer
• Utilized Ic / Part: LMX2485E
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -

The LMX2485E Evaluation Board simplifies evaluation of the LMX2485E 2.6 GHz/0.8 GHz PLLatinum™ dual
frequency synthesizer. The primary function of this board is to evaluate the LMX2485E device performance at
low RF input frequencies, which is 50 MHz.
The board enables all performance measurements with no additional support circuitry. The evaluation board
consists of a LMX2485E device, an RF VCO module and RF loop filters built with discrete components. The
SMA flange mount connectors are provided for an external reference input, an RF VCO output, and a power
connection. A cable assembly is bundled with the evaluation board for connecting to a PC through the parallel
port. By means of MICROWIRE™ serial port emulation, the CodeLoader software included can be run on a
PC to facilitate the LMX2485E internal register programming for evaluation and measurement.
The VCO used on the evaluation board is a Sirenza VCO190-52U. Using a 5 Volt supply, the frequency range
of the Sirenza VCO190-52U is specified to cover 51 to 53 MHz with a 0.5V to 4.5 V control. The LMX2485E
device is powered from a 3.3 V regulated supply, which gives a Charge Pump output dc voltage swing of 0.5 to
2.7 volts for optimum performance. Charge Pump output voltage can be measured at TP1. With these
voltages, the VCO output frequency will nominally be 48.6 to 49.6 MHz. No IF VCO is attached. Therefore, the
IF section is powered down for all measurements.
Loop Bandwidth
Phase Margin
6800 pF
Lock Time
CPoRF
100 nF
1.0 KΩ
tolerance in 450 us w/o CSR
48.6 – 49.6 MHz to 1 kHz
L M X 2 4 8 5 E
2.2 kΩ
48.0 deg
4.5 kHz
General Description
1800 pF
E V A L U A T I O N
RF Loop Filter
VCO
3
B O A R D
Output Frequency
Pole Ratio T3 /T1
Capacitance
VCO Supply
Comparison
@ 200 KHz
PLL Supply
Frequency
VCO Used
VCO Input
VCO Gain
Roll-Off
Settings for Operation
Kφ
O P E R A T I N G
Other Information
48.6 – 49.6 MHz
VCO190-52U
2.5 MHz/Volt
I N S T R U C T I O N S
8X (760 uA)
1000 kHz
SIRENZA
3.3 Volts
-68.4 dB
29.8 %
820 pF
5 Volts