ADL5501AKSZ-R21 datasheet(23/28 Pages) AD

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ADL5501

Rev. B | Page 23 of 2

DRIFT OVER A REDUCED TEMPERATURE RANGE

Due to the repeatability of the performance from part to part,

compensation can be applied to reduce the effects of temperature

drift and linearity error. To detect larger dynamic ranges at

lower frequencies, the transfer function at ambient can be

calibrated, thus eliminating the linearity error. This technique

is discussed in detail in the Calibration for Improved Accuracy

section. Figure 55 shows that the dynamic range within ±0.5 dB

error improves to 30 dB by using this method.

Figure 53 shows the error over temperature for a 1.9 GHz input

signal. Error due to drift over temperature consistently remains

within ±0.25 dB and begins to exceed this limit only when the

ambient temperature goes above +25°C and below −10°C. For

all frequencies using a reduced temperature range, higher

measurement accuracy is achievable.

1.00

–1.00

–0.75

–0.50

–0.25

0.25

0.50

0.75

–25

–20

–15

–10

–5

INPUT (dBm rms)

+85°C

+70°C

+50°C

+35°C

+25°C

+15°C

0°C

–10°C

–25°C

–40°C

–3

–2

–1

–25

–20

–15

–10

–5

INPUT (dBm)

Figure 53. Typical Drift at 1.9 GHz for Various Temperatures

Figure 55. Output Delta from +25°C Output Voltage for

12 Devices at −40°C and +85°C, Frequency = 50 MHz, Supply = 5.0 V

OPERATION BELOW 100 MHz

The ADL5501 works at frequencies below 100 MHz but exhibits a

slightly higher linearity error. Figure 54 shows the error distribution

of 12 devices at 50 MHz over temperature. When compared to

an ideal linear transfer function at ambient, the error of the

ADL5501 over temperature remains within ±0.5 dB for the

central 20 dB of the dynamic range. At the higher input power

levels, the error grows as the response becomes nonlinear. The

typical slope and intercept at 50 MHz are 4.5 V/V rms and

0.04 V, respectively.

EVALUATION BOARD

Figure 56 shows the schematic of the ADL5501 evaluation

board. The layout and silkscreen of the evaluation board layers

are shown in Figure 57 and Figure 58. The board is powered by

a single supply in the 2.7 V to 5.5 V range. The power supply is

decoupled by 100 pF and 0.1 μF capacitors. Table 5 details the

various configuration options of the evaluation board.

Problems caused by impedance mismatch can arise when the

evaluation board is used to examine ADL5501 performance.

One way to reduce these problems is to put a coaxial 3 dB atten-

uator on the RFIN SMA connector. Mismatches at the source,

cable, and cable interconnection, as well as those occurring on

the evaluation board, can cause these problems.

–3

–2

–1

–25

–20

–15

–10

–5

INPUT (dBm)

A simple (and common) example of such a problem is triple

travel due to mismatch at both the source and the evaluation

board. Here the signal from the source reaches the evaluation

board, and mismatch causes a reflection. When that reflection

reaches the source mismatch, it causes a new reflection, which

travels back to the evaluation board, adding to the original signal

incident at the board. The resulting voltage varies with both

cable length and frequency dependence on the relative phase of

the initial and reflected signals. Placing the 3 dB pad at the input of

the board improves the match at the board and, thus, reduces

the sensitivity to mismatches at the source. When such precau-

tions are taken, measurements are less sensitive to cable length and

other fixture issues. In an actual application when the distance

between the ADL5501 and the source is short and well defined,

this 3 dB attenuator is not needed.

Figure 54. Temperature Drift Distributions for 12 Devices at −40°C, +25°C,

and +85°C vs. +25°C Linear Reference, Frequency = 50 MHz, Supply = 5.0 V

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