adl5505 Analog Devices, Inc., adl5505 Datasheet - Page 17

• Manufacturer Part Number: adl5505
• Description: 450 Mhz To 6000 Mhz Trupwr Detector Adl5505
• Manufacturer: Analog Devices, Inc.

POWER CONSUMPTION
The quiescent current consumption of the ADL5505 varies
linearly with the size of the input signal from approximately
1.8 mA for no signal up to 8.5 mA at an input level of 0.7 V rms
(10 dBm, referred to 50 Ω) as shown in Figure 27. There is
little variation in supply current across power supply voltage
or temperature.
In applications requiring power saving, it is recommended that the
ADL5505 be disabled while idle by removing the power supply to
the device.
DEVICE CALIBRATION AND ERROR CALCULATION
Because slope and intercept vary from device to device, board-
level calibration must be performed to achieve high accuracy.
In general, calibration is performed by applying two input power
levels to the ADL5505 and measuring the corresponding output
voltages. The calibration points are generally chosen to be within
the linear operating range of the device. The best-fit line is
characterized by calculating the conversion gain (or slope) and
intercept using the following equations:
where:
V
V
INx
VRMSx
is the rms input voltage to RFIN.
Gain = (V
Intercept = V
Supply = 3 V, Frequency = 900 MHz; Square-Domain Filter Open;
is the voltage output at VRMS.
Figure 40. Output Response to Various RF Input Pulse Levels,
VRMS2
VRMS1
C
− V
OUT
− (Gain × V
= 0.1 μF with Parallel 1 kΩ
VRMS1
)/(V
1ms/DIV
400mV rms RF INPUT
250mV rms
160mV rms
70mV rms
IN2
− V
IN1
)
IN1
)
PULSED RFIN
VRMS
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(3)
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Once gain and intercept are calculated, an equation can be
written that allows calculation of an (unknown) input power
based on the measured output voltage.
For an ideal (known) input power, the law conformance error of
the measured data can be calculated as
Figure 41 shows a plot of the error at 25°C, the temperature
at which the ADL5505 is calibrated. Note that the error is not 0;
this is because the ADL5505 does not perfectly follow the ideal
linear equation, even within its operating region. The error at
the calibration points is, however, equal to 0 by definition.
Figure 41 also shows error plots for the output voltage at −40°C
and +85°C. These error plots are calculated using the gain and
intercept at 25°C. This is consistent with calibration in a mass
production environment where calibration at temperature is not
practical.
+85°C vs. +25°C Linear Reference, 1900 MHz Frequency, 3.0 V Supply
Figure 41. Error from Linear Reference vs. Input at −40°C, +25°C, and
V
ERROR (dB) =
20 × log [(V
IN
–1
–2
–3
3
2
1
0
= (V
–25
VRMS
–20
VRMS, MEASURED
− Intercept)/Gain
–15
–10
+25°C
–40°C
INPUT (dBm)
− Intercept)/(Gain × V
–5
+85°C
0
5
ADL5505
10
IN, IDEAL
15
)] (6)
(5)