LMX2433 datasheet(12/53 Pages) TI1

12 / 53 page

LMX2430, LMX2433, LMX2434

SNAS187D – FEBRUARY 2003 – REVISED JANUARY 2016

www.ti.com

8 Parameter Measurement Information

8.1 Bench Test Setups

8.1.1 LMX243x Charge-Pump Test Setup

Figure 23. Charge-Pump Current Test Setup

Figure 23 shows the setup required to measure the RF charge-pump sink current of the LMX243x device. The

same setup is used for the LMX2430PW evaluation board. The purpose of this test is to assess the functionality

of the RF charge pump. The IF charge pump is evaluated in the same way.

This setup uses an open-loop configuration. A power supply is connected to VCC. By means of a signal

generator, a 10-MHz signal is typically applied to the FinRF pin. The signal is one of two inputs to the phase /

frequency detector (PFD). The 3-dB pad provides a 50-

Ω match between the PLL and the signal generator. The

OSCin pin is tied to Vcc. This establishes the other input to the PFD. Alternatively, this input can be tied directly

to the ground plane. The EN and ENosc pins are also both tied to Vcc. A semiconductor parameter analyzer is

connected to the CPoutRF pin and used to measure the sink, source, and tri-state leakage currents.

Let Fr represent the frequency of the signal applied to the OSCin pin, which is simply zero in this case (DC), and

let Fp represent the frequency of the signal applied to the FinRF pin. The PFD is sensitive to the rising edges of

Fr and Fp. Assuming positive VCO characteristics (RF_CPP bit = 1); the charge pump turns ON, and sinks

current when the first rising edge of Fp is detected. Because Fr has no rising edge, the charge pump continues to

sink current indefinitely. In order to measure the RF charge-pump source current, the RF_CPP bit is simply set to

0 (negative VCO characteristics) in CodeLoader. Similarly, in order to measure the tri-state leakage current, the

RF_CPT bit is set to 1.

Submit Documentation Feedback

Product Folder Links: LMX2430 LMX2433 LMX2434

LMX2433 Datasheet(PDF) 12 Page - Texas Instruments