lmx2377u National Semiconductor Corporation, lmx2377u Datasheet - Page 26

• Manufacturer Part Number: lmx2377u
• Description: Lmx2377u Pllatinum? Ultra Low Power Dual Frequency Synthesizer For Rf Personal Communications 2.5 Ghz/1.2 Ghz
• Manufacturer: National Semiconductor Corporation

www.national.com
Test Setups
The block diagram above illustrates the setup required to
measure the LMX2377U device’s Main charge pump sink
current. The same setup is used for the LMX2370TMEB/
LMX2370SLEEB Evaluation Boards. The Aux charge pump
measurement setup is similar to the Main charge pump
measurement setup. The purpose of this test is to assess the
functionality of the Main charge pump.
This setup uses an open loop configuration. A power supply
is connected to V
CROWIRE power supply, Vµc, is tied to V
signal generator, a 10 MHz signal is typically applied to the
f
detector. The 3 dB pad provides a 50 Ω match between the
PLL and the signal generator. The OSC
This establishes the other input to the phase detector. Alter-
natively, this input can be tied directly to the ground plane.
With the D
eter Analyzer in this way, the sink, source, and TRI-STATE
currents can be measured by simply toggling the Phase
Detector Polarity and Charge Pump State states in Code
IN
Main pin. The signal is one of two inputs to the phase
o
Main pin connected to a Semiconductor Param-
cc
and swept from 2.7V to 5.5V. The MI-
in
cc
pin is tied to V
. By means of a
LMX2377U Charge Pump Test Setup
cc
.
26
Loader. Similarly, the LOW and HIGH currents can be mea-
sured by switching the Charge Pump Gain’s state between
1X and 4X in Code Loader.
Let F
OSC
represent the frequency of the signal applied to the f
pin. The phase detector is sensitive to the rising edges of F
and F
pump turns ON and sinks current when the first rising edge
of F
pump continues to sink current indefinitely.
Toggling the Phase Detector Polarity state to negative
VCO characteristics allows the measurement of the Main
charge pump source current. Likewise, selecting TRI-STATE
(TRI-STATE ID
Code Loader facilitates the measurement of the TRI-STATE
current.
The measurements are repeated at different temperatures,
namely T
p
in
r
p
is detected. Since F
represent the frequency of the signal applied to the
pin, which is simply zero in this case (DC), and let F
. Assuming positive VCO characteristics; the charge
A
= -40˚C, +25˚C, and +85˚C.
o
Main Bit = 1) for Charge Pump State in
r
has no rising edge, the charge
20022650
IN
Main
p
r