LMX2364 National Semiconductor Corporation, LMX2364 Datasheet - Page 20

• Manufacturer Part Number: LMX2364
• Description: 2.6 Ghz Pllatinum Fractional Rf Frequency Synthesizer With 850 Mhz Integer If Frequency Synthesizer
• Manufacturer: National Semiconductor Corporation

www.national.com
Test Setup Procedures
Sensitivity
Sensitivity is defined as the power level limits beyond which
the output of the counter being tested is off by 1 Hz or more
of its expected value. It is typically measured over frequency,
voltage, and temperature. In order to test sensitivity, the
MUX[3:0] word is programmed to the appropriate value. The
counter value isthen programmed to a fixed value and a
frequency counter is set to monitor the frequency of this pin.
The expected frequency at the Ftest/LD pin should be the
signal generator frequency divided by twice the correspond-
ing counter value. The factor of two comes in because the
LMX2364 has a flip-flop which divides this frequency by two
to make the duty cycle 50% in order to make it easier to read
with the frequency counter. The frequency counter input
impedance should be set to high impedance.
In order to perform the measurement, the temperature, fre-
quency, and voltage is set to a fixed value and the power
Frequency Input Pin
OSCinRF
OSCinIF
FinRF
FinIF
DC Blocking Capacitor
100 pF
100 pF
1 nF
1 nF
Corresponding Counter
20
IF_R/RF_R
RF_R
RF_N
IF_N
level of the signal is varied. Note that the power level at the
part is assumed to be 4 dB less than the signal generator
power level. This accounts for 1 dB for cable losses and 3 dB
for the pad. The power level range where the frequency is
correct at the Ftest/LD pin to within 1 Hz accuracy is re-
corded for the sensitivity limits. The temperature, frequency,
and voltage can be varied in order to produce a family of
sensitivity curves. Since this is an open-loop test, the charge
pump is set to TRI-STATE and the unused side of the PLL
(RF or IF) is powered down when not being tested.
For this part, there are actually four frequency input pins,
although there is only one frequency test pin (Ftest/LD). The
conditions specific to each pin are show above.
Default Counter Value
5000
5000
50
50
11 (RF R/2)
12 (RF N/2)
MUX Value
10 (IF N/2)
20050674
9 (IF R/2)