AD8318 datasheet(21/24 Pages) AD

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AD8318

Rev. A | Page 21 of 24

CHARACTERIZATION SETUP AND METHODS

VIDEO

OUT

RF OUT

–7dBm

R AND S SMT06

TEKTRONIX

TDS51504

CH1* CH3* TRIGGER

VOUT

GND

AD8318

VPOS

VSET

INHI

INLO

52.3

1nF

*50

TERMINATION

3dB

SPLITTER

The general hardware configuration used for the AD8318

characterization is shown in Figure 46. The primary setup used for

characterization is measurement mode. The characterization board

is similar to the customer evaluation board with the exception that

the RF input has a Rosenberger SMA connector and R10 has

changed to a 1 kΩ resistor to remove cable capacitance from the

bench characterization setup. Slope and intercept are calculated in

this data sheet and in the production environment using linear

regression from −50 dBm to −10 dBm. The slope and intercept

generate an ideal line. Log conformance error is the difference from

the ideal line and the measured output voltage for a given tempera-

ture in dB. For additional information on the error calculation, refer

to the Device Calibration and Error Calculation section.

Figure 46. Pulse Response Measurement Test Setup

To measure noise spectral density, the 0 Ω resistor in series with

the VOUT pin is replaced with a 1 μF dc blocking capacitor.

The capacitor is used because the Rohde & Schwarz FSEA

spectrum analyzer cannot handle dc voltages at its RF input.

The CLPF pin is left open for data collected for Figure 18. For

Figure 19, a 1 μF capacitor is placed between CLPF and ground.

The large capacitor filters the noise from the detector stages of

the log amp. Noise spectral density measurements are taken

using the FSEA and the SMT06 signal generator. The signal

generator frequency is set to 2.2 GHz. The spectrum analyzer

has a span of 10 Hz, resolution bandwidth of 50 Hz, video

bandwidth of 50 Hz, and averages the signal 100 times. Data is

adjusted to account for the dc blocking capacitor impedance on

the output at lower frequencies.

The hardware configuration for pulse response measurement

replaces the 0 Ω series resistor at the VOUT pin with a 40 Ω resistor;

the CLPF pin remains open. Pulse response time is measured using a

Tektronix TDS51504 Digital Phosphor Oscilloscope. Both channels

on the scope are configured for 50 Ω termination. The 10 Ω internal

series resistance at VOUT, combined with the 40 Ω resistor,

attenuates the output voltage level by two. RF input frequency is set

to 100 MHz with −10 dBm at the input of the device. The RF burst is

generated using a Rohde & Schwarz SMT06 with the pulse option

with a period of 1.5 μs, a width of 0.1 μs, and a pulse delay of 0.04 μs.

The output response is triggered using the video output from the

SMT06. Refer to Figure 46 for an overview of the test setup.

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