adl5504 Analog Devices, Inc., adl5504 Datasheet - Page 17

• Manufacturer Part Number: adl5504
• Description: 450 Mhz To 6000 Mhz Trupwr Detector
• Manufacturer: Analog Devices, Inc.

POWER CONSUMPTION, ENABLE, AND POWER-
ON/POWER-OFF RESPONSE TIME
The quiescent current consumption of the ADL5504 varies
linearly with the size of the input signal from approximately
1.8 mA for no signal up to 9 mA at an input level of 0.7 V rms
(10 dBm, referred to 50 Ω). There is little variation in supply
current across power supply voltage or temperature, as shown in
Figure 27.
The ADL5504 can be disabled either by pulling the ENBL (Pin 6)
to COMM (Pin 4) or by removing the power supply to the device.
Disabling the device via the ENBL function reduces the leakage
current to less than 1 μA. When the device is disabled, the output
impedance increases to approximately 5.5 kΩ on VRMS.
The turn-on time and pulse response is strongly influenced
by the sizes of the square-domain filter and the output shunt
capacitor. Figure 42 shows a plot of the output response to an
RF pulse on the RFIN pin, with a 0.1 μF output filter capacitor and
a no square-domain filter capacitor. The falling edge is particularly
dependent on the output shunt capacitance, as shown in Figure 42.
To improve the falling edge of the enable and pulse responses, a
resistor can be placed in parallel with the output shunt capacitor.
The added resistance helps to discharge the output filter capacitor.
Although this method reduces the power-off time, the added
load resistor also attenuates the output (see the Output Drive
Capability and Buffering section).
Figure 42. Output Response to Various RF Input Pulse Levels, 3 V Supply,
900 MHz Frequency, Square-Domain Filter Open, C
1ms/DIV
400mV rms RF INPUT
250mV rms
160mV rms
70mV rms
PULSED RFIN
OUT
= 0.1 μF
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The square-domain filter improves the rms accuracy for high
crest factors (see the Selecting the Square-Domain Filter and
Output Low-Pass Filter section), but it can hinder the response
time. For optimum response time and low ac residual, both the
square-domain filter and the output filter should be used. The
square-domain filter at FLTR can be reduced to improve response
time, and the remaining ac residual can be decreased by using
the output filter, which has a smaller time constant.
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 ADL5504 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
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
INx
VRMSx
is the rms input voltage to RFIN.
Gain = (V
Intercept = V
V
ERROR (dB) = 20 × log [(V
(Gain × V
IN
is the voltage output at VRMS.
3 V Supply, 900 MHz Frequency, Square-Domain Filter Open,
Figure 43. Output Response to Various RF Input Pulse Levels,
= (V
VRMS
VRMS2
IN, IDEAL
− Intercept)/Gain
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
VRMS, MEASURED
IN2
IN1
− V
)
IN1
PULSED RFIN
)
− Intercept)/
ADL5504
(3)
(4)
(5)
(6)