ADL5902-EVALZ AD [Analog Devices], ADL5902-EVALZ Datasheet - Page 17

• Manufacturer Part Number: ADL5902-EVALZ
• Description: 50 MHz to 9 GHz 65 dB TruPwr Detector
• Manufacturer: AD [Analog Devices]

there is no temperature variation contribution to the absolute value
of V
For CW signals,
However, signals with large crest factors include low pseudo-
random frequency content that must be either filtered out or
sampled and averaged out (see the Choosing a Value for C
section for more information).
TEMPERATURE SENSOR INTERFACE
The ADL5902 provides a temperature sensor output with a
scaling factor of the output voltage of approximately 4.9 mV/°C.
The output is capable of sourcing 4 mA and sinking 50 μA
maximum at 25°C. An external resistor can be connected from
TEMP to COMM to provide additional current sink capability.
The typical output voltage at 25°C is approximately 1.4 V.
VREF INTERFACE
The VREF pin provides an internally generated voltage reference
for the user. The VREF voltage is a temperature stable 2.3 V
reference that is capable of sourcing 4 mA and sinking 50 μA
maximum. An external resistor can be connected from VREF to
COMM to provide additional current sink capability. The
voltage on this pin can be used to drive the TADJ/PWDN and
VTGT pins.
TEMPERATURE COMPENSATION INTERFACE
While the ADL5902 has a highly stable measurement output
with respect to temperature using proprietary techniques, for
optimal performance, the output temperature drift must be
compensated for using the TADJ pin. The absolute value of
compensation varies with frequency and V
recommended voltages for V
error of typically ±0.5 dB or better over the intended temperature
range (−40°C < T
V
TGT
OUT
Freq
= 0.8 V.
.
LP
≈ 67.7 × 10
Figure 38. TEMP Interface Simplified Schematic
INTERNAL
INTERNAL
Figure 39. VREF Interface Simplified Schematic
VOLTAGE
VPAT
A
< +85°C) when driven single-ended and
−6
/(C
LPF
TADJ
)
to maintain a temperature drift
COMM
COMM
VPOS
VPOS
12kΩ
4kΩ
16kΩ
TGT
. Table 4 shows the
TEMP
VREF
LPF
(14)
Rev. 0 | Page 17 of 28
Table 4. Recommended V
Frequency
100 MHz
700 MHz
900 MHz
1.9 GHz
2.14 GHz
2.6 GHz
3.5 GHz
5.8 GHz
The values in Table 4 were chosen to give the best drift
performance at the high end of the usable dynamic range
over the −40°C to +85°C temperature range. There is often a
trade off in setting values, and optimizing for one area of the
dynamic range may mean less than optimal drift performance
at other input amplitudes.
Compensating the device for temperature drift using TADJ
allows for great flexibility. If the user requires minimum
temperature drift at a given input power, a subset of the
dynamic range, or even over a different temperature range than
shown in this data sheet, the V
monitoring V
amplitude of interest. The optimal V
temperature drift at a given power and frequency is the value of
V
Varying V
temperatures near 25°C; however, the compensation circuit
has more and more effect as the temperature departs farther
from 25°C.
The TADJ pin has a high input impedance and can be conven-
iently driven from an external source or from an attenuated
value of V
voltage divider values to generate the required voltage from
V
(see Figure 54). V
also input RF amplitude; however, the amount of change is
unlikely to result in a significant effect on the final temperature
TADJ
REF
Figure 40. Effect of V
. The resistors are shown in the evaluation board schematic
where the output has minimum movement.
2.83
2.81
2.79
2.77
2.75
2.73
0.1
REF
TADJ
using a resistor divider. Table 4 gives suggested
OUT
has only a very slight effect on V
V
0.5
0.4
0.4
0.4
0.4
0.45
0.5
0.95
0.2
TADJ
over the temperature at the frequency and
REF
(V)
TADJ
does change slightly with temperature and
0.3
at Various Temperatures, 2.14 GHz, −10 dBm
R9 in Figure 54
(Ω)
1430
1430
1430
1430
1430
1430
1430
1430
TADJ
0.4
V
TADJ
for Selected Frequencies
TADJ
can be swept while
(V)
0.5
TADJ
to achieve minimum
0.6
R12 in Figure 54
(Ω)
402
301
301
301
301
348
402
1007
OUT
0.7
at device
ADL5902
+125°C
+105°C
+85°C
+55°C
+25°C
–40°C
–20°C
0°C
0.8