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Preliminary Technical Data

ADL5519

Rev. PrB | Page 20 of 27

TEMPERATURE COMPENSATION ADJUSTMENT

The ADL5519 has a highly stable measurement output with

respect to temperature. However, when the RF inputs exceed a

frequency of 600 MHz, the output temperature drift must be

compensated for using ADJ[A, B] for optimal performance.

Proprietary techniques are used to compensate for the temper-

ature drift. The absolute value of compensation varies with

frequency and circuit board material. Table 4 shows

recommended voltages for ADJ[A, B] to maintain a

temperature drift error of typically ±0.5 dB or better over the

entire rated temperature range with the recommended baluns.

Table 4: Recommended ADJ[A,B] Voltage Levels

Frequency

Recommended ADJ[A,B] Voltage

50 MHz

TBD

100 MHz

TBD

900 MHz

TBD

1.8 GHz

TBD

1.9 GHz

TBD

2.2 GHz

TBD

3.6 GHz

TBD

5.3 GHZ

TBD

5.8 GHz

TBD

8 GHz

TBD

Compensating the device for temperature drift using ADJ[A, B]

allows for great flexibility. If the user requires minimum temper-

ature drift at a given input power or subset of the dynamic range,

the ADJ[A, B] voltage can be swept while monitoring OUT[A, B]

over temperature. Figure 22 shows the result of such an exercise.

The value of ADJ[A, B] where the output has minimum

movement (approximately 0.77 V for the example in Figure 22)

is the recommended voltage for ADJ[A, B] to achieve minimum

temperature drift at a given power and frequency.

Figure 22. OUTA vs. ADJA over Temp. Pin = −30 dBm, 1.9 GHz

The ADJ[A, B] input has high input impedance. The input can

be conveniently driven from an attenuated value of VREF using

a resistor divider, if desired.

Figure 23 shows a simplified schematic representation of the

ADJ[A, B] interface.

COMR

ICOMP

ADJ[A,B]

VTADJ

VREF

ADL5519

Figure 23. ADJ[A, B] Interface Simplified Schematic

DEVICE CALIBRATION AND ERROR CALCULATION

The measured transfer function of the ADL5519 at 2.14 GHz is

shown in Figure 24. The figure shows plots of both output

voltage vs. input power and calculated error vs. input power. As

the input power varies from −50 dBm to 0 dBm, the output

voltage varies from 0.4 V to about 2.8 V.

Figure 24. Transfer Function at 2.14 GHz.

Because slope and intercept vary from device to device, board-

level calibration must be performed to achieve high accuracy.

The equation for output voltage can be written as

VOUT = Slope × (PIN − Intercept)

Where Slope is the change in output voltage divided by the

change in power (dB), and Intercept is the calculated power at

which the output voltage would be 0 V. (Note that Intercept is a

theoretical value; the output voltage can never achieve 0 V).

In general, the calibration is performed by applying two known

signal levels to the ADL5519’s input and measuring the

corresponding output voltages. The calibration points are

generally chosen to be within the linear-in-dB operating range

of the device (see the Specifications section for more details).

Calculation of the slope and intercept is done using the

equations:

Slope = (VOUT1 − VOUT2)/(PIN1 − PIN2)

Intercept = PIN1 − (VOUT1/Slope)

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