ADL5519ACPZ-R2 AD [Analog Devices], ADL5519ACPZ-R2 Datasheet - Page 20

• Manufacturer Part Number: ADL5519ACPZ-R2
• Description: 1 MHz to 10 GHz, 50 dB Dual Log Detector/Controller
• Manufacturer: AD [Analog Devices]

Preliminary Technical Data
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
50 MHz
100 MHz
900 MHz
1.8 GHz
1.9 GHz
2.2 GHz
3.6 GHz
5.3 GHZ
5.8 GHz
8 GHz
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.
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.
Figure 22. OUTA vs. ADJA over Temp. Pin = −30 dBm, 1.9 GHz
Recommended ADJ[A,B] Voltage
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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.
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
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:
V
Slope = (V
Intercept = P
OUT
= Slope × (P
V
Figure 23. ADJ[A, B] Interface Simplified Schematic
TADJ
VREF
OUT1
Figure 24. Transfer Function at 2.14 GHz.
IN1
ADJ[A,B]
− V
− (V
IN
OUT2
− Intercept)
OUT1
)/(P
/Slope)
ADL5519
COMR
IN1
− P
IN2
)
COMR
I
COMP
ADL5519