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参数资料
| 型号： | LMX2377UTMX/NOPB |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | PLL合成/DDS/VCOs |
| 英文描述： | PLL FREQUENCY SYNTHESIZER, 2500 MHz, PDSO20 |
| 封装： | PLASTIC, TSSOP-20 |
| 文件页数： | 19/44页 |
| 文件大小： | 3181K |
| 代理商： | LMX2377UTMX/NOPB |
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Test Setups
LMX2377U Charge Pump Test Setup
20022650
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
cc and swept from 2.7V to 5.5V. The MI-
CROWIRE power supply, Vc, is tied to V
cc. By means of a
signal generator, a 10 MHz signal is typically applied to the
f
IN Main pin. The signal is one of two inputs to the phase
detector. The 3 dB pad provides a 50
match between the
PLL and the signal generator. The OSC
in pin is tied to Vcc.
This establishes the other input to the phase detector. Alter-
natively, this input can be tied directly to the ground plane.
With the D
o Main pin connected to a Semiconductor Param-
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
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
r represent the frequency of the signal applied to the
OSC
in pin, which is simply zero in this case (DC), and let Fp
represent the frequency of the signal applied to the f
IN Main
pin. The phase detector is sensitive to the rising edges of F
r
and F
p. Assuming positive VCO characteristics; the charge
pump turns ON and sinks current when the first rising edge
of F
p is detected. Since Fr has no rising edge, the charge
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
o Main Bit = 1) for Charge Pump State in
Code Loader facilitates the measurement of the TRI-STATE
current.
The measurements are repeated at different temperatures,
namely T
A = -40C, +25C, and +85C.
LMX2377U
www.national.com
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