LMX2364SLEX datasheet(20/39 Pages) NSC

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Test Setup Procedures

Sensitivity

20050674

Frequency Input Pin

DC Blocking Capacitor

Corresponding Counter

Default Counter Value

MUX Value

OSCinIF

1 nF

IF_R/RF_R

5000

9 (IF R/2)

FinIF

100 pF

IF_N

5000

10 (IF N/2)

OSCinRF

1 nF

RF_R

11 (RF R/2)

FinRF

100 pF

RF_N

12 (RF N/2)

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

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.

LMX2364SLEX Datasheet(PDF) 20 Page - National Semiconductor (TI)

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