AD AD8361 Lf to 2.5 ghz trupwrâ ¢ detector Datasheet

a
LF to 2.5 GHz
TruPwr™ Detector
AD8361
FEATURES
Calibrated RMS Response
Excellent Temperature Stability
Up to 30 dB Input Range at 2.5 GHz
700 mV rms, 10 dBm re 50 ⍀ Maximum Input
ⴞ0.25 dB Linear Response Up to 2.5 GHz
Single Supply Operation: 2.7 V to 5.5 V
Low Power: 3.3 mW at 3 V Supply
Rapid Power-Down to Less than 1 ␮A
FUNCTIONAL BLOCK DIAGRAMS
micro_SOIC
VPOS
RFIN
INTERNAL FILTER
i
␹2
FLTR
TRANSCONDUCTANCE
CELLS
␹2
APPLICATIONS
Measurement of CDMA, W-CDMA, QAM, Other
Complex Modulation Waveforms
RF Transmitter or Receiver Power Measurement
AD8361
ERROR
AMP
i
ⴛ 7.5
BUFFER
ADD
OFFSET
BAND-GAP
REFERENCE
PWDN
VRMS
SREF
COMM
IREF
PRODUCT DESCRIPTION
The AD8361 is a mean-responding power detector for use in highfrequency receiver and transmitter signal chains, up to 2.5 GHz.
It is very easy to apply. It requires only a single supply between
2.7 V and 5.5 V, power supply decoupling capacitor and an
input coupling capacitor in most applications. The output is a
linear-responding dc voltage with a conversion gain of 7.5 V/V rms.
An external filter capacitor can be added to increase the averaging time constant.
SOT-23-6L
VPOS
RFIN
␹2
PWDN
2.8
SUPPLY
REFERENCE MODE
2.6
INTERNAL
REFERENCE MODE
V rms – Volts
2.0
1.6
1.4
GROUND
REFERENCE MODE
1.0
0.8
ⴛ 7.5
BUFFER
VRMS
BAND-GAP
REFERENCE
The AD8361 has three operating modes to accommodate a
variety of analog-to-digital converter requirements:
0.6
1. Ground referenced mode, in which the origin is zero;
0.4
0.2
0.0
ERROR
AMP
The AD8361 is intended for true power measurement of simple
and complex waveforms. The device is particularly useful for
measuring high crest-factor (high peak-to-rms ratio) signals, such
as CDMA and W-CDMA.
1.8
1.2
i
COMM
2.4
2.2
FLTR
AD8361
TRANSCONDUCTANCE
CELLS
3.0
INTERNAL FILTER
i
␹2
0
0.1
0.2
0.3
RFIN – V rms
0.4
0.5
Figure 1. Output in the Three Reference Modes, Supply 3 V,
Frequency 1.9 GHz (SOT-23-6L Package Ground Reference
Mode Only)
2. Internal reference mode, which offsets the output 350 mV
above ground;
3. Supply reference mode, which offsets the output to VS/7.5.
The AD8361 is specified for operation from –40°C to +85°C and
is available in 8-lead micro_SOIC and 6-lead SOT packages.
It is fabricated on a proprietary high fT silicon bipolar process.
TruPwr is a trademark of Analog Devices, Inc.
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2000
= 25ⴗC, V = 3 V, f
AD8361–SPECIFICATIONS (Tnoted.)
A
Parameter
Condition
SIGNAL INPUT INTERFACE
Frequency Range1
Linear Response Upper Limit
(Input RFIN)
S
RF
= 900 MHz, ground reference output mode, unless otherwise
Min
VS = 3 V
Equivalent dBm re 50 Ω
VS = 5 V
Equivalent dBm re 50 Ω
Dynamic Range
± 0.25 dB Error4
± 1 dB Error
± 2 dB Error
Intercept-Induced Dynamic
Range Reduction 5, 6
Deviation from CW Response
OUTPUT INTERCEPT5
Ground Reference Mode (GRM)
Internal Reference Mode (IRM)
Supply Reference Mode (SRM)
POWER-DOWN INTERFACE
PWDN HI Threshold
PWDN LO Threshold
Power-Up Response Time
Unit
2.5
GHz
mV rms
dBm
mV rms
dBm
Ω储pF
(Input RFIN to Output V rms)
7.5
fRF = 100 MHz, VS = 5 V
Error Referred to Best Fit Line 3
CW Input, –40°C < TA < +85°C
CW Input, –40°C < TA < +85°C
CW Input, –40°C < TA < +85°C
CW Input, VS = 5 V, –40°C < TA < +85°C
Internal Reference Mode
Supply Reference Mode, VS = 3.0 V
Supply Reference Mode, VS = 5.0 V
5.5 dB Peak-to-Average Ratio (IS95 Reverse Link)
12 dB Peak-to-Average Ratio (W-CDMA 4 Channels)
18 dB Peak-to-Average Ratio (W-CDMA 15 Channels)
Inferred from Best Fit Line 3
0 V at SREF, VS at IREF
fRF = 100 MHz, VS = 5 V
0 V at SREF, IREF Open
fRF = 100 MHz, VS = 5 V
0 V at IREF, 3 V at SREF
fRF = 100 MHz, VS = 5 V
0 V at IREF, VS at SREF
6.5
8.5
14
23
26
30
1
1
1.5
0.2
1.0
1.2
+150
350
300
500
400
590
750
VS/7.5
2.7 ≤ VS ≤ 5.5 V, –40°C < TA < +85°C
2.7 ≤ VS ≤ 5.5 V, –40°C < TA < +85°C
2 pF at FLTR Pin, 224 mV rms at RFIN
100 nF at FLTR Pin, 224 mV rms at RFIN
VS – 0.5
–40°C < TA < +85°C
0 mV rms at RFIN, PWDN Input LO 7
GRM or IRM, 0 mV rms at RFIN, PWDN Input HI
SRM, 0 mV rms at RFIN, PWDN Input HI
2.7
0.1
5
320
<1
5.5
1.1
<1
10 × VS
V/V rms
V/V rms
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
0
–50
PWDN Bias Current
POWER SUPPLIES
Operating Range
Quiescent Current
Power-Down Current
Max
390
4.9
660
9.4
225储1
Input Impedance2
RMS CONVERSION
Conversion Gain
Typ
V
mV
mV
mV
mV
mV
V
V
V
µs
µs
µA
V
mA
µA
µA
NOTES
1
Operation at arbitrarily low frequencies is possible; see Applications section.
2
Figure 13 and Figure 40 show impedance vs. frequency for the micro_SOIC and SOT respectively.
3
Calculated using linear regression.
4
Compensated for output reference temperature drift; see Applications section.
5
SOT-23-6L operates in ground reference mode only.
6
The available output swing, and hence the dynamic range, is altered by both supply voltage and reference mode; see Figures 35 and 36.
7
Supply current is input level dependant; see Figure 12.
Specifications subject to change without notice.
–2–
REV. A
AD8361
ABSOLUTE MAXIMUM RATINGS 1
PIN FUNCTION DESCRIPTIONS
Supply Voltage VS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 V
SREF, PWDN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 V, VS
IREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VS – 0.3 V, VS
RFIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 V rms
Equivalent Power re 50 Ω . . . . . . . . . . . . . . . . . . . 13 dBm
Internal Power Dissipation2 . . . . . . . . . . . . . . . . . . . . 200 mW
SOT-23-6L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 mW
micro_SOIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200 mW
Maximum Junction Temperature . . . . . . . . . . . . . . . . . 125°C
Operating Temperature Range . . . . . . . . . . . –40°C to +85°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Lead Temperature Range (Soldering 60 sec) . . . . . . . . . 300°C
NOTES
1
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
2
Specification is for the device in free air.
SOT-23-6L: θJA = 230°C/W; θJC = 92°C/W.
micro_SOIC: θJA = 200°C/W; θJC = 44°C/W.
Pin
Micro SOT Name
1
6
2
3
5
4
4
5
6
2
3
7
1
PIN CONFIGURATIONS
micro_SOIC
VPOS 1
AD8361
8 SREF
IREF 2
7 VRMS
RFIN 3
6 FLTR
PWDN 4
5 COMM
SOT-23-6L
VRMS
1
AD8361
8
6 VPOS
COMM 2
5 RFIN
FLTR
4 PWDN
3
Description
VPOS
Supply Voltage Pin. Operational range
2.7 V to 5.5 V.
IREF
Output Reference Control Pin. Internal reference mode enabled when pin
is left open. Otherwise, this pin should
be tied to VPOS. DO NOT ground this
pin.
RFIN
Signal Input Pin. Must be driven from
an ac-coupled source. The low frequency
real input impedance is 225 Ω.
PWDN Power-Down Pin. For the device to
operate as a detector it needs a logical
low input (less than 100 mV). When
a logic high (greater than VS – 0.5 V)
is applied, the device is turned off and
the supply current goes to nearly zero
(ground and internal reference mode
less than 1 µA, supply reference mode
VS divided by 100 kΩ).
COMM Device Ground Pin.
FLTR
By placing a capacitor between this pin
and VPOS, the corner frequency of the
modulation filter is lowered. The onchip filter is formed with 27 pF储2 kΩ
for small input signals.
VRMS Output Pin. Near-rail-to-rail voltage
output with limited current drive capabilities. Expected load >10 kΩ to ground.
SREF
Supply Reference Control Pin. To enable supply reference mode this pin
must be connected to VPOS, otherwise it should be connected to COMM
(ground).
ORDERING GUIDE
Model
Temperature Range
Package Description
Package Option
AD8361ARM*
AD8361ARM-REEL
AD8361ARM-REEL7
AD8361ART-REEL
AD8361ART-REEL7
AD8361-EVAL
AD8361ART-EVAL
–40°C to +85°C
Tube, 8-Lead micro_SOIC
13" Tape and Reel
7" Tape and Reel
13" Tape and Reel
7" Tape and Reel
Evaluation Board micro_SOIC
Evaluation Board SOT-23-6L
RM-8
RT-6
*Device branded as J3A.
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although
the AD8361 features proprietary ESD protection circuitry, permanent damage may occur on
devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are
recommended to avoid performance degradation or loss of functionality.
REV. A
–3–
WARNING!
ESD SENSITIVE DEVICE
AD8361–Typical Performance Characteristics
2.8
3.0
900MHz
2.6
2.5
2.4
2.0
2.2
100MHz
1900MHz
1.5
1.0
1.8
1.6
ERROR – dB
OUTPUT – Volts
2.0
2.5GHz
1.4
1.2
1.0
–2.0
0.4
–2.5
0.2
0
0.1
0.2
0.3
INPUT – V rms
0.4
–3.0
0.01
0.5
Figure 2. Output vs. Input Level, Frequencies 100 MHz,
900 MHz, 1900 MHz, and 2500 MHz, Supply 2.7 V, Ground
Reference Mode, micro_SOIC
5.5
2.5
4.5
2.0
5.0V
1.5
4.0
3.0V
1.0
ERROR – dB
3.5
3.0
2.5
2.7V
0.5
0
–0.5
–1.0
1.5
–1.5
1.0
–2.0
0.5
–2.5
0
0.1
0.2
0.3
0.4
0.5
INPUT – V rms
0.6
0.7
–3.0
0.01
0.8
Figure 3. Output vs. Input Level, Supply 2.7 V, 3.0 V, 5.0 V,
and 5.5 V, Frequency 900 MHz
5.0
IS95
REVERSE LINK
4.5
0.4
(+5dBm)
0.1
(–7dBm)
INPUT – V rms
3.0
5.5V
2.0
0.02
(–21dBm)
Figure 5. Error from Linear Reference vs. Input Level,
3 Sigma to Either Side of Mean, Sine Wave, Supply 3.0 V,
Frequency 900 MHz
5.0
0.0
MEAN ⴞ3 SIGMA
–1.5
0.6
OUTPUT – Volts
0
–0.5
–1.0
0.8
0.0
0.5
MEAN ⴞ3 SIGMA
0.02
(–21dBm)
0.6
(+8.6dBm)
0.1
(–7dBm)
INPUT – V rms
Figure 6. Error from Linear Reference vs. Input Level,
3 Sigma to Either Side of Mean, Sine-Wave, Supply 5.0 V,
Frequency 900 MHz
3.0
CW
2.5
2.0
4.0
1.5
1.0
ERROR – dB
OUTPUT – Volts
3.5
3.0
2.5
WCDMA
4- AND 15-CHANNEL
2.0
IS95
REVERSE LINK
CW
0.5
0.0
–0.5
4-CHANNEL
–1.0
1.5
15-CHANNEL
–1.5
1.0
–2.0
0.5
0.0
–2.5
0
0.1
0.2
0.3
0.4
0.5
INPUT – V rms
0.6
0.7
–3.0
0.01
0.8
0.02
0.1
0.2
0.6
1.0
INPUT – V rms
Figure 7. Error from CW Linear Reference vs. Input with
Different Waveforms Sine Wave (CW), IS95 Reverse Link,
W-CDMA 4-Channel and W-CDMA 15-Channel, Supply
3.0 V, Frequency 900 MHz
Figure 4. Output vs. Input Level with Different Waveforms
Sine Wave (CW), IS95 Reverse Link, W-CDMA 4-Channel
and W-CDMA 15-Channel, Supply 5.0 V
–4–
REV. A
3.0
3.0
2.5
2.5
2.0
2.0
1.5
1.5
1.0
1.0
ERROR – dB
0.5
0
–0.5
–1.0
0
–0.5
–2.0
–2.5
–2.5
0.02
(–21dBm)
0.1
(–7dBm)
INPUT – V rms
–3.0
0.01
0.4
(+5dBm)
Figure 8. Error from CW Linear Reference vs. Input,
3 Sigma to Either Side of Mean, IS95 Reverse Link Signal,
Supply 3.0 V, Frequency 900 MHz
11
2.5
10
2.0
9
SUPPLY CURRENT – mA
1.5
1.0
0.5
0
–0.5
MEAN ⴞ3 SIGMA
–1.5
0.02
(–21dBm)
0.4
(+5dBm)
0.1
(–7dBm)
INPUT – V rms
Figure 11. Output Delta from +25 °C vs. Input Level,
3 Sigma to Either Side of Mean Sine Wave, Supply 3.0 V,
Frequency 1900 MHz, Temperature –40 °C to +85 °C
3.0
–1.0
–40ⴗC
–1.5
–2.0
–3.0
0.01
ERROR – dB
0.5
–1.0
MEAN ⴞ3 SIGMA
–1.5
+85ⴗC
VS = 5V
INPUT OUT
OF RANGE
–40ⴗC
8
VS = 3V
INPUT OUT
OF RANGE
7
6
5
+25ⴗC
+85ⴗC
+25ⴗC
4
+85ⴗC
3
2
–2.0
–2.5
1
–3.0
0.01
0
0.02
(–21dBm)
0.6
(+8.6dBm)
0.1
(–7dBm)
INPUT – V rms
Figure 9. Error from CW Linear Reference vs. Input Level,
3 Sigma to Either Side of Mean, IS95 Reverse Link Signal,
Supply 5.0 V, Frequency 900 MHz
–40ⴗC
0
0.1
0.2
0.3
0.4
0.5
INPUT – V rms
0.6
0.7
0.8
Figure 12. Supply Current vs. Input Level, Supplies 3.0 V,
and 5.0 V, Temperatures –40 °C, +25 °C, and +85 °C
3.0
250
+25ⴗC
2.5
1.8
+85ⴗC
1.6
2.0
1.5
+85ⴗC
1.0
ERROR – dB
SHUNT RESISTANCE – ⍀
200
0.5
0
–0.5
–1.0
–40ⴗC
–1.5
–40ⴗC
1.4
+85ⴗC
150
1.2
1.0
100
+25ⴗC
0.8
–40ⴗC
SHUNT CAPACITANCE – pF
ERROR – dB
AD8361
50
–2.0
0.6
–2.5
–3.0
0.01
0.02
(–21dBm)
0.1
(–7dBm)
INPUT – V rms
Figure 10. Output Delta from +25 °C vs. Input Level,
3 Sigma to Either Side of Mean Sine Wave, Supply 3.0 V,
Frequency 900 MHz, Temperature –40 °C to +85°C
REV. A
0
0.4
(+5dBm)
0
500
1500
1000
FREQUENCY – MHz
2000
0.4
2500
Figure 13. Input Impedance vs. Frequency, Supply 3 V,
Temperatures –40 °C, +25 °C, and +85 °C, micro_SOIC (See
Applications for SOT-23-6L Data)
–5–
AD8361
0.03
0.18
0.16
0.14
0.01
GAIN CHANGE – V/V rms
INTERCEPT CHANGE – Volts
0.02
0.00
–0.01
–0.02
MEAN ⴞ3 SIGMA
–0.03
0.12
0.10
MEAN ⴞ3 SIGMA
0.08
0.06
0.04
0.02
0.00
–0.02
–0.04
–0.04
–0.05
–0.06
–40
–20
0
20
40
TEMPERATURE – ⴗC
60
80
–40
100
Figure 14. Output Reference Change vs. Temperature,
Supply 3 V, Ground Reference Mode
–20
0
20
40
TEMPERATURE – ⴗC
60
80
100
Figure 17. Conversion Gain Change vs. Temperature,
Supply 3 V, Ground Reference Mode, Frequency 900 MHz
0.02
0.18
0.14
GAIN CHANGE – V/V rms
INTERCEPT CHANGE – Volts
0.16
0.01
0.00
–0.01
MEAN ⴞ3 SIGMA
–0.02
0.12
0.10
MEAN ⴞ3 SIGMA
0.08
0.06
0.04
0.02
0.00
–0.02
–0.04
–0.03
–40
–20
0
20
40
TEMPERATURE – ⴗC
60
80
–0.06
100
–40
Figure 15. Output Reference Change vs. Temperature,
Supply 3 V, Internal Reference Mode (micro_SOIC Only)
0
20
40
TEMPERATURE – ⴗC
60
80
100
Figure 18. Conversion Gain Change vs. Temperature,
Supply 3 V, Internal Reference Mode, Frequency 900 MHz
(micro_SOIC Only)
0.03
0.18
0.02
0.16
0.01
0.12
0.14
GAIN CHANGE – V/V rms
INTERCEPT CHANGE – Volts
–20
0.00
–0.01
–0.02
MEAN ⴞ3 SIGMA
–0.03
0.10
MEAN ⴞ3 SIGMA
0.08
0.06
0.04
0.02
0.00
–0.02
–0.04
–0.04
–0.05
–40
–20
0
20
40
TEMPERATURE – ⴗC
60
80
–0.06
100
–40
Figure 16. Output Reference Change vs. Temperature,
Supply 3 V, Supply Reference Mode (micro_SOIC Only)
–20
0
20
40
TEMPERATURE – ⴗC
60
80
100
Figure 19. Conversion Gain Change vs. Temperature,
Supply 3 V, Supply Reference Mode, Frequency 900 MHz
(micro_SOIC Only)
–6–
REV. A
AD8361
GATE PULSE FOR
900MHz RF TONE
PWDN INPUT
500mV PER
VERTICAL
DIVISION
370mV
370mV
270mV
270mV
500mV PER
VERTICAL
DIVISION
RF INPUT
RF INPUT
67mV
67mV
25mV
25mV
5␮s PER HORIZONTAL DIVISION
2␮s PER HORIZONTAL DIVISION
Figure 23. Output Response Using Power-Down Mode
for Various RF Input Levels, Supply 3 V, Frequency
900 MHz, No Filter Capacitor
Figure 20. Output Response to Modulated Pulse Input
for Various RF Input Levels, Supply 3 V, Modulation
Frequency 900 MHz, No Filter Capacitor
GATE PULSE FOR
900MHz RF TONE
PWDN INPUT
370mV
370mV
500mV PER
VERTICAL
DIVISION
270mV
270mV
500mV PER
VERTICAL
DIVISION
RF INPUT
67mV
67mV
25mV
25mV
50␮s PER HORIZONTAL DIVISION
20␮s PER HORIZONTAL DIVISION
Figure 21. Output Response to Modulated Pulse Input
for Various RF Input Levels, Supply 3 V, Modulation
Frequency 900 MHz, 0.01 µ F Filter Capacitor
HPE3631A
POWER SUPPLY
C4
0.01␮F
HPE3631A
POWER SUPPLY
AD8361
VPOS
SREF
IREF
VRMS
C1
C4
0.01␮F
C3
RFIN
R1
75⍀
Figure 24. Output Response Using Power-Down Mode
for Various RF Input Levels, Supply 3 V, Frequency
900 MHz, 0.01 µ F Filter Capacitor
TEK TDS784C
SCOPE
C2
100pF
FLTR
0.1␮F
PWDN
TEK TDS784C
SCOPE
C2
100pF
AD8361
TEK P6204
FET PROBE
VPOS
SREF
IREF
VRMS
C1
C5
100pF
C3
RFIN
R1
75⍀
COMM
HP8648B
SIGNAL
GENERATOR
HP8648B
SIGNAL
GENERATOR
Figure 22. Hardware Configuration for Output Response
to Modulated Pulse Input
REV. A
RF INPUT
FLTR
0.1␮F
PWDN
TEK P6204
FET PROBE
C5
100pF
COMM
HP8110A
PULSE
GENERATOR
Figure 25. Hardware Configuration for Output Response
Using Power-Down Mode
–7–
AD8361
7.8
16
14
VS = 3V
7.4
7.2
12
7.0
10
PERCENT
CONVERSION GAIN – V/V rms
7.6
6.8
6.6
8
6.4
6
6.2
4
6.0
2
5.8
5.6
100
0
6.9
1000
CARRIER FREQUENCY – MHz
7.0
7.2
7.6
7.4
CONVERSION GAIN – V/V rms
7.8
Figure 29. Conversion Gain Distribution Frequency
100 MHz, Supply 5 V, Sample Size 3000
Figure 26. Conversion Gain Change vs. Frequency, Supply
3 V, Ground Reference Mode, Frequency 100 MHz to
2500 MHz, Representative Device
12
RF
INPUT
SUPPLY
370mV
12
500mV PER
VERTICAL
DIVISION
10
PERCENT
270mV
8
6
67mV
4
25mV
2
20␮s PER HORIZONTAL DIVISION
0
0.32
Figure 27. Output Response to Gating On Power Supply,
for Various RF Input Levels, Supply 3 V, Modulation
Frequency 900 MHz, 0.01 µ F Filter Capacitor
AD811
50⍀
0.34
0.38
0.42
0.36
0.40
IREF MODE INTERCEPT – Volts
0.44
Figure 30. Output Reference, Internal Reference Mode,
Supply 5 V, Sample Size 3000 (micro_SOIC Only)
12
12
HP8110A
PULSE
GENERATOR
10
TEK TDS784C
SCOPE
C4
0.01␮F
C2
100pF
AD8361
VPOS
SREF
IREF
VRMS
C1
C3
RFIN
R1
75⍀
8
PERCENT
732⍀
FLTR
0.1␮F
PWDN
TEK P6204
FET PROBE
6
4
C5
100pF
2
COMM
0
HP8648B
SIGNAL
GENERATOR
0.64
0.66
0.68
0.72
0.70
SREF MODE INTERCEPT – Volts
0.74
0.76
Figure 31. Output Reference, Supply Reference Mode,
Supply 5 V, Sample Size 3000 (micro_SOIC Only)
Figure 28. Hardware Configuration for Output Response
to Power Supply Gating Measurements
–8–
REV. A
AD8361
CIRCUIT DESCRIPTION
The AD8361 is an rms-responding (mean power) detector providing an approach to the exact measurement of RF power that
is basically independent of waveform. It achieves this function
through the use of a proprietary technique in which the outputs
of two identical squaring cells are balanced by the action of a
high-gain error amplifier.
The signal to be measured is applied to the input of the first
squaring cell, which presents a nominal (LF) resistance of 225 Ω
between the pin RFIN and COMM (connected to the ground
plane). Since the input pin is at a bias voltage of about 0.8 V
above ground, a coupling capacitor is required. By making this
an external component, the measurement range may be extended
to arbitrarily low frequencies.
The AD8361 responds to the voltage, VIN, at its input, by squaring
this voltage to generate a current proportional to VIN squared.
This is applied to an internal load resistor, across which is connected a capacitor. These form a low-pass filter, which extracts
the mean of VIN squared. Although essentially voltage-responding,
the associated input impedance calibrates this port in terms of
equivalent power. Thus 1 mW corresponds to a voltage input of
447 mV rms. In the Application section it is shown how to match
this input to 50 Ω.
The voltage across the low-pass filter, whose frequency may
be arbitrarily low, is applied to one input of an error-sensing
amplifier. A second identical voltage-squaring cell is used to
close a negative feedback loop around this error amplifier.
This second cell is driven by a fraction of the quasi-dc output
voltage of the AD8361. When the voltage at the input of the
second squaring cell is equal to the rms value of VIN, the loop
is in a stable state, and the output then represents the rms value of
the input. The feedback ratio is nominally 0.133, making the
rms-dc conversion gain ×7.5, that is
VOUT = 7.5 × VIN rms
By completing the feedback path through a second squaring cell,
identical to the one receiving the signal to be measured, several
benefits arise. First, scaling effects in these cells cancel; thus, the
overall calibration may be accurate, even though the open-loop
response of the squaring cells taken separately need not be.
Note that in implementing rms-dc conversion, no reference
voltage enters into the closed-loop scaling. Second, the tracking
in the responses of the dual cells remains very close over temperature, leading to excellent stability of calibration.
The squaring cells have very wide bandwidth with an intrinsic
response from dc to microwave. However, the dynamic range
of such a system is fairly small, due in part to the much larger
dynamic range at the output of the squaring cells. There are
practical limitations to the accuracy with which very small error
signals can be sensed at the bottom end of the dynamic range,
arising from small random offsets; these set the limit to the
attainable accuracy at small inputs.
eventual loss of square-law conformance. Consequently, the top
end of their response range occurs at a fairly large input level
(about 700 mV rms) while preserving a reasonably accurate
square-law response. The maximum usable range is, in practice,
limited by the output swing. The rail-to-rail output stage can
swing from a few millivolts above ground to less than 100 mV
below the supply. An example of the output induced limit: given
a gain of 7.5 and assuming a maximum output of 2.9 V with a 3 V
supply; the maximum input is (2.9 V rms)/7.5 or 390 mV rms.
Filtering
An important aspect of rms-dc conversion is the need for
averaging (the function is root-MEAN-square). For complex RF
waveforms such as occur in CDMA, the filtering provided by
the on-chip low-pass filter, while satisfactory for CW signals above
100 MHz, will be inadequate when the signal has modulation
components that extend down into the kilohertz region. For this
reason, the FLTR pin is provided: a capacitor attached between
this pin and VPOS can extend the averaging time to very low
frequencies.
Offset
An offset voltage can be added to the output (when using the
micro_SOIC version) to allow the use of A/D converters whose
range does not extend down to ground. However, accuracy at
the low end will be degraded because of the inherent error in this
added voltage. This requires that the pin IREF (internal reference)
should be tied to VPOS and SREF (supply reference) to ground.
In the IREF mode, the intercept is generated by an internal
reference cell, and is a fixed 350 mV, independent of the supply
voltage. To enable this intercept, IREF should be open-circuited,
and SREF should be grounded.
In the SREF mode, the voltage is provided by the supply. To
implement this mode, tie IREF to VPOS and SREF to VPOS. The
offset is then proportional to the supply voltage, and is 400 mV
for a 3 V supply and 667 mV for a 5 V supply.
USING THE AD8361
Basic Connections
Figures 32, 33, and 34 show the basic connections for the
micro_SOIC version AD8361 in its three operating modes. In all
modes, the device is powered by a single supply of between 2.7 V
and 5.5 V. The VPOS pin is decoupled using 100 pF and 0.01 µF
capacitors. The quiescent current of 1.1 mA in operating mode
can be reduced to 1 µA by pulling the PWDN pin up to VPOS.
A 75 Ω external shunt resistance combines with the ac-coupled
input to give an overall broadband input impedance near 50 Ω.
Note that the coupling capacitor must be placed between the input and the shunt impedance. Input impedance and input coupling
are discussed in more detail below.
The input coupling capacitor combines with the internal input
resistance (Figure 13) to give a high-pass corner frequency
given by the equation
On the other hand, the squaring cells in the AD8361 have
a “Class-AB” aspect; the peak input is not limited by their
quiescent bias condition, but is determined mainly by the
REV. A
f3 dB =
–9–
1
2 π × CC × RIN
AD8361
With the 100 pF capacitor shown in Figures 32–34, the highpass corner frequency is about 8 MHz.
+VS 2.7 – 5.5V
the output headroom decreases. The response for lower supply
voltages is similar (in the supply referenced mode, the offset is
smaller), but the dynamic range will be reduced further, as headroom decreases. Figure 36 shows the response of the AD8361 to
a CW input for various supply voltages.
100pF
5.0
0.01␮F
AD8361
1
VPOS
SREF 8
2
IREF
VRMS 7
SUPPLY REF
4.5
V rms
RFIN
R1
75⍀
4.0
INTERNAL REF
3.5
3
RFIN
4
PWDN
FLTR 6
OUTPUT – Volts
CC
100pF
CFLTR
COMM 5
Figure 32. Basic Connections for Ground Referenced Mode
GROUND REF
3.0
2.5
2.0
1.5
+VS 2.7 – 5.5V
1.0
0.5
100pF
0.01␮F
0.0
1
VPOS
SREF 8
2
IREF
VRMS 7
3
RFIN
FLTR 6
4
PWDN
CC
R1
75⍀
0.2
0.3
0.4
0.5
INPUT – V rms
5.5
CFLTR
100pF
0.1
0.6
COMM 5
5.5V
4.5
OUTPUT – Volts
100pF
AD8361
VPOS
SREF 8
2
IREF
VRMS 7
3
RFIN
FLTR 6
R1
75⍀
4
PWDN
3.0V
3.5
3.0
2.5
2.0
1.0
0.5
CC
0.0
CFLTR
100pF
2.7V
1.5
V rms
RFIN
5.0V
4.0
+VS 2.7 – 5.5V
1
0.8
5.0
Figure 33. Basic Connections for Internal Reference Mode
0.01␮F
0.7
Figure 35. Output Swing for Ground, Internal and Supply
Referenced Mode. VPOS = 5 V (micro_SOIC Only)
V rms
RFIN
0
AD8361
0
0.1
COMM 5
0.2
0.3
0.4
0.5
INPUT – V rms
0.6
0.7
0.8
Figure 36. Output Swing for Supply Voltages of 2.7 V,
3.0 V, 5.0 V and 5.5 V (micro_SOIC Only)
Figure 34. Basic Connections for Supply Referenced Mode
The output voltage is nominally 7.5 times the input rms voltage
(a conversion gain of 7.5 V/V rms). Three different modes of
operation are set by the pins SREF and IREF. In addition to the
ground referenced mode shown in Figure 32, where the output
voltage swings from around near ground to 4.9 V on a 5.0 V
supply, two additional modes allow an offset voltage to be added to
the output. In the internal reference mode, (Figure 33), the
output voltage swing is shifted upward by an internal reference
voltage of 350 mV. In supply referenced mode (Figure 34), an
offset voltage of VS/7.5 is added to the output voltage. Table I
summarizes the connections, output transfer function and minimum output voltage (i.e., zero signal) for each mode.
Dynamic Range
Output Swing
Reference
Mode
IREF
Ground
Internal
Supply
VPOS
OPEN
VPOS
Figure 35 shows the output swing of the AD8361 for a 5 V supply
voltage for each of the three modes. It is clear from Figure 35,
that operating the device in either internal reference mode or
supply referenced mode, will reduce the effective dynamic range as
Because the AD8361 is a linear responding device with a nominal transfer function of 7.5 V/V rms, the dynamic range in dB is
not clear from plots such as Figure 35. As the input level is
increased in constant dB steps, the output step size (per dB)
will also increase. Figure 37 shows the relationship between the
output step size (i.e., mV/dB) and input voltage for a nominal
transfer function of 7.5 V/V rms.
Table I. Connections and Nominal Transfer Function for
Ground, Internal, and Supply Reference Modes
–10–
SREF
Output
Intercept
(No Signal)
Output
COMM
COMM
VPOS
Zero
0.350 V
VS/7.5
7.5 VIN
7.5 VIN + 0.350 V
7.5 VIN + VS/7.5
REV. A
AD8361
A number of options exist for input matching. For operation at
multiple frequencies, a 75 Ω shunt to ground, as shown in Figure
39a, will provide the best overall match. For use at a single frequency, a resistive or a reactive match can be used. By plotting the
input impedance on a Smith Chart, the best value for a
resistive match can be calculated. The VSWR can be held below
1.5 at frequencies up to 1 GHz, even as the input impedance
varies from part to part. (Both input impedance and input
capacitance can vary by up to ± 20% around their nominal values.)
At very high frequencies (i.e., 1.8 GHz to 2.5 GHz), a shunt
resistor will not be sufficient to reduce the VSWR below 1.5.
Where VSWR is critical, remove shunt component and insert
an inductor in series with the coupling capacitor as shown in
Figure 39b.
700
600
mV/dB
500
400
300
200
100
0
0
100
200
300
400
500
INPUT – mV
600
700
800
Figure 37. Idealized Output Step Size as Function of Input
Voltage
Table II gives recommended shunt resistor values for various
frequencies and series inductor values for high frequencies. The
coupling capacitor, CC, essentially acts as an ac-short and plays
no intentional part in the matching.
Plots of output voltage vs. input voltage result in a straight line. It
may sometimes be more useful to plot the error on a logarithmic scale, as shown in Figure 38. The deviation of the plot for
the ideal straight line characteristic is caused by output clipping
at the high end and by signal offsets at the low end. It should
however be noted that offsets at the low end can be either positive or negative, so that this plot could also trend upwards at the
low end. Figures 5, 6, 8, and 9 show a ± 3 sigma distribution of
device error for a large population of devices.
CC
RFIN
RFIN
RSH
AD8361
a. Broadband Resistor Match
LM
CC
RFIN
RFIN
2.0
AD8361
1.5
b. Series Inductor Match
1.0
ERROR – dB
2.5GHz
0.5
CM
100MHz
CC
RFIN
RFIN
0.0
1.9GHz
LM
AD8361
–0.5
100MHz
–1.0
c. Narrowband Reactive Match
–1.5
900MHz
–2.0
0.01
0.02
(–21dBm)
0.1
(–7dBm)
0.4
(+5dBm)
1.0
RSERIES
RFIN
INPUT – V rms
Figure 38. Representative Unit, Error in dB vs. Input Level,
VS = 2.7 V
RFIN
AD8361
d. Attenuating the Input Signal
It is also apparent in Figure 38 that the error plot tends to
shift to the right with increasing frequency. Because the input
impedance decreases with frequency, the voltage actually applied
to the input will also tend to decrease (assuming a constant source
impedance over frequency). The dynamic range is almost constant over frequency, but with a small decrease in conversion gain
at high frequency.
Figure 39. Input Coupling/Matching Options
Table II. Recommended Component Values for Resistive or
Inductive Input Matching (Figures 39a and 39b)
Input Coupling and Matching
The input impedance of the AD8361 decreases with increasing
frequency in both its resistive and capacitive components (Figure
13). The resistive component varies from 225 Ω at 100 MHz
down to about 95 Ω at 2.5 GHz.
REV. A
CC
–11–
Frequency
Matching Component
100 MHz
800 MHz
900 MHz
1800 MHz
1900 MHz
2500 MHz
63.4 Ω Shunt
75 Ω Shunt
75 Ω Shunt
150 Ω Shunt or 4.7 nH Series
150 Ω Shunt or 4.7 nH Series
150 Ω Shunt or 2.7 nH Series
AD8361
Alternatively, a reactive match can be implemented using a shunt
inductor to ground and a series capacitor as shown in Figure
39c. A method for hand calculating the appropriate matching
components is shown on page 12 of the AD8306 data sheet.
Matching in this manner results in very small values for CM,
especially at high frequencies. As a result, a stray capacitance as
small as 1 pF can significantly degrade the quality of the match.
The main advantage of a reactive match is the increase in sensitivity that results from the input voltage being “gained up” (by
the square root of the impedance ratio) by the matching network.
Table III shows recommended values for reactive matching.
Table III. Recommended Values for a Reactive Input Match
(Figure 39c)
Frequency
MHz
CM
pF
LM
nH
100
800
900
1800
1900
2500
16
2
2
1.5
1.5
1.5
180
15
12
4.7
4.7
3.3
provides adequate filtering for all frequencies above 240 MHz
(i.e., ten times the frequency at the output of the squarer, which
is twice the input frequency). However, signals with high peakto-average ratios, such as CDMA or W-CDMA signals, and
with low frequency components, require additional filtering.
TDMA signals, such as GSM, PDC, or PHS have a peak-toaverage ratio that is close to that of a sinusoid, and the internal
filter is adequate.
The filter capacitance of the AD8361 can be augmented by
connecting a capacitor between Pin 6 (FLTR) and VPOS.
Table IV shows the effect of several capacitor values for various
communications standards with high peak-to-average ratios along
with the residual ripple at the output, in peak-to-peak and rms
volts. Note that large filter capacitors will increase the enable
and pulse response times, as discussed below.
Table IV. Effect of Waveform and CFILT on Residual AC
Waveform
CFILT
IS95 Reverse Link
Open
0.01 µF
Input Coupling Using a Series Resistor
Figure 39d shows a technique for coupling the input signal
into the AD8361, which may be applicable where the input signal
is much larger than the input range of the AD8361. A series
resistor combines with the input impedance of the AD8361 to
attenuate the input signal. Since this series resistor forms a
divider with the frequency-dependent input impedance, the
apparent gain changes greatly with frequency. However, this
method has the advantage of very little power being “tapped
off” in RF power transmission applications. If the resistor is large
compared to the transmission line’s impedance then the VSWR of
the system is relatively unaffected.
0.1 µF
IS95 8-Channel
Forward Link
0.01 µF
0.1 µF
W-CDMA 15
Channel
0.01 µF
1.7
250
200
1.4
150
1.1
100
0.8
50
0.5
0
0
500
1000
1500
2000
2500
FREQUENCY – MHz
3000
CAPACITANCE – pF
RESISTANCE – ⍀
0.1 µF
0.2
3500
Figure 40. Input Impedance vs. Frequency, Supply 3 V,
SOT-23-6L
Selecting the Filter Capacitor
The AD8361’s internal 27 pF filter capacitor is connected in
parallel with an internal resistance that varies with signal level
from 2 kΩ for small signals to 500 Ω for large signals. The
resulting low-pass corner frequency between 3 MHz and 12 MHz
Output
V dc
Residual AC
mV p-p mV rms
0.5
1.0
2.0
0.5
1.0
2.0
0.5
1.0
2.0
0.5
1.0
2.0
0.5
1.0
2.0
0.5
1.0
2.0
0.5
1.0
2.0
550
1000
2000
40
160
430
20
40
110
290
975
2600
50
190
670
225
940
2500
45
165
550
100
180
360
6
20
60
3
6
18
40
150
430
7
30
95
35
135
390
6
25
80
Operation at Low Frequencies
Although the AD8361 is specified for operation up to 2.5 GHz,
there is no lower limit on the operating frequency. It is only necessary to increase the input coupling capacitor to reduce the
corner frequency of the input high-pass filter (use an input resistance of 225 Ω for frequencies below 100 MHz). It is also
necessary to increase the filter capacitor so that the signal at the
output of the squaring circuit is free of ripple. The corner frequency will be set by the combination of the internal resistance of
2 kΩ and the external filter capacitance.
Power Consumption, Enable and Power-On
The quiescent current consumption of the AD8361 varies with
the size of the input signal from about 1 mA for no signal up to
7 mA at an input level of 0.66 V rms (9.4 dBm re 50 Ω). If the
input is driven beyond this point, the supply current increases
steeply (see Figure 12). There is little variation in quiescent
current with power supply voltage.
–12–
REV. A
AD8361
The AD8361 can be disabled either by pulling the PWDN (Pin 4)
to VPOS or by simply turning off the power to the device. While
turning off the device obviously eliminates the current consumption, disabling the device reduces the leakage current to less
than 1 µA. Figures 23 and 24 show the response of the output of
the AD8361 to a pulse on the PWDN pin, with no capacitance and
with a filter capacitance of 0.01 µF respectively; the turn-on time is
a function of the filter capacitor. Figure 27 shows a plot of the
output response to the supply being turned on (i.e., PWDN is
grounded and VPOS is pulsed) with a filter capacitor of 0.01 µF
Again, the turn-on time is strongly influenced by the size of the
filter capacitor.
current is required (>10 mA), the AD8051, which also has railto-rail capability, can be used, down to a supply voltage of 3 V. It
can deliver up to 45 mA of output current.
5V
100pF
0.01␮F
0.01␮F
VPOS
VOUT
AD8031
AD8361
15V/V rms
COMM PWDN
5k⍀
If the input of the AD8361 is driven while the device is disabled
(PWDN = VPOS), the leakage current of less than 1 µA will
increase as a function of input level. When the device is disabled, the output impedance increases to around 16 kΩ.
5k⍀
a. Slope of 15 V/V rms
Volts to dBm Conversion
5V
In many of the plots, the horizontal axis is scaled in both rms
volts and dBm. In all cases, dBm are calculated relative to an
impedance of 50 Ω. To convert between dBm and volts in a
50 Ω. system, the following equations can be used. Figure 40
shows this conversion in graphical form.
0.01␮F
100pF
10k⍀
VPOS
VOUT
0.01␮F
5k⍀
AD8361
5k⍀
 (V rms )2

 50 Ω
Power ( dBm ) = 10 log 
0.001 W





2
 = 10 log (20 (V rms ) )


b. Slope of 3.75 V/V rms
5V
0.01␮F
V rms =
 dBm 
0.001 W × 50 Ω × log –1
 =
 10 
(
log –1 dBm / 10
)
100pF
0.01␮F
VPOS
VOUT
20
AD8031
AD8361
V rms
1
0.1
+10
c. Slope of 7.5 V/V rms
0
Figure 42. Output Buffering Options
–10
–30
–40
0.001
Figure 41. Conversion from dBm to rms Volts
Output Drive Capability and Buffering
The AD8361 is capable of sourcing an output current of approximately 3 mA. If additional current is required, a simple buffering
circuit can be used as shown in Figure 42c. Similar circuits
can be used to increase or decrease the nominal conversion gain of
7.5 V/V rms (Figure 42a and 42b). In Figure 42b, the AD8031
buffers a resistive divider to give a slope of 3.75 V/V rms. In Figure
42a, the op amp’s gain of two increases the slope to 15 V/V rms.
Using other resistor values, the slope can be changed to an
arbitrary value. The AD8031 rail-to-rail op amp, used in these
examples can swing from 50 mV to 4.95 V on a single 5 V supply
and operate at supply voltages down to 2.7 V. If high output
REV. A
7.5V/V rms
COMM PWDN
dBm
+20
–20
0.01
3.75V/V rms
AD8031
COMM PWDN
OUTPUT REFERENCE TEMPERATURE DRIFT
COMPENSATION
The error due to low temperature drift of the AD8361 can be
reduced if the temperature is known. Many systems incorporate
a temperature sensor; the output of the sensor is typically digitized, facilitating a software correction. Using this information,
only a two-point calibration at ambient is required.
The output voltage of the AD8361 at ambient (25°C) can be
expressed by the equation:
(
)
VOUT = GAIN × VIN + VOS
where GAIN is the conversion gain in V/V rms and VOS is the
extrapolated output voltage for an input level of 0 V. GAIN and
VOS (also referred to as Intercept and Output Reference) can be
calculated at ambient using a simple two-point calibration;
that is, by measuring the output voltages for two specific input
levels. Calibration at roughly 35 mV rms (–16 dBm) and
250 mV rms (+1 dBm) is recommended for maximum linear
dynamic range. However, alternative levels and ranges can be
–13–
AD8361
(
chosen to suit the application. GAIN and VOS are then calculated
using the equations:
(V
GAIN =
(V
OUT 2
IN 2
− VOUT1
− VIN 1
(
)
(
)
The equation can be rewritten to yield a temperature compensated value for VIN.
)
VOS = VOUT1 − GAIN × VIN 1
)
VOUT = GAIN × VIN + VOS + DRIFTVOS × TEMP − 25°C
VIN =
)
Both GAIN and VOS drift over temperature. However, the drift
of VOS has a bigger influence on the error relative to the output.
This can be seen by inserting data from Figures 14 and 17 (conversion gain and intercept drift) into the equation for VOUT. These
plots are consistent with Figures 10 and 11 which show that the
error due to temperature drift decreases with increasing input
level. This results from the offset error having a diminishing
influence with increasing level on the overall measurement error.
From Figure 14, the average Intercept drift is 0.43 mV/°C from
–40°C to +25°C and 0.17 mV/°C from +25°C to +85°C. For a
less rigorous compensation scheme, the average drift over the
complete temperature range can be calculated:
(V
OUT
(
− VOS − DRIFTVOS × TEMP − 25°C
))
GAIN
EVALUATION BOARD
Figures 43 and 46 show the schematic of the AD8361 evaluation board. Note that uninstalled components are drawn in as
dashed. The layout and silkscreen of the component side are
shown in Figures 44, 45, 47, and 48. The board is powered by a
single supply in the range, 2.7 V to 5.5 V. The power supply
is decoupled by 100 pF and 0.01 µF capacitors. Additional
decoupling, in the form of a series resistor or inductor in R6,
can also be added. Table V details the various configuration
options of the evaluation board.
 0.010 V − ( −0.028 V ) 
DRIFTVOS ( V / °C ) = 

 +85°C − ( −40°C ) 
= 0.000304 V/°C
With the drift of VOS included, the equation for VOUT becomes:
Table V. Evaluation Board Configuration Options
Component
Function
Default Condition
TP1, TP2
SW1
Ground and Supply Vector Pins.
Device Enable. When in Position A, the PWDN pin is connected to +VS and
the AD8361 is in power-down mode. In Position B, the PWDN pin is grounded,
putting the device in operating mode.
Operating Mode. Selects either Ground Referenced Mode, Internal Reference
Mode or Supply Reference Mode. See Table I for more details.
Input Coupling. The 75 Ω resistor in position R2 combines with the AD8361’s
internal input impedance to give a broadband input impedance of around 50 Ω.
For more precise matching at a particular frequency, R2 can be replaced by a
different value (see Input Matching and Figure 39).
Capacitor C1 ac-couples the input signal and creates a high-pass input filter
whose corner frequency is equal to approximately 8 MHz. C1 can be increased
for operation at lower frequencies. If resistive attenuation is desired at the input,
series resistor R1, which is nominally 0 Ω, can be replaced by an appropriate value.
Power Supply Decoupling. The nominal supply decoupling of 0.01 µF and
100 pF. A series inductor or small resistor can be placed in R6 for additional
decoupling.
Filter Capacitor. The internal 50 pF averaging capacitor can be augmented
by placing a capacitance in C5.
Output Loading. Resistors and capacitors can be placed in C4 and R5 to
load test V rms.
Not Applicable
SW1 = B
SW2/SW3
C1, R2
C2, C3, R6
C5
C4, R5
–14–
SW2 = A, SW3 = B
(Ground Reference Mode)
R2 = 75 Ω (Size 0402)
C1 = 100 pF (Size 0402)
C2 = 0.01 µF (Size 0402)
C3 = 100 pF (Size 0402)
R6 = 0 Ω (Size 0402)
C5 = 1 nF (Size 0603)
C4 = R5 = Open
(Size 0603)
REV. A
AD8361
VPOS
C3
100pF
TP2
C2
0.01␮F
R6
0⍀
VS
VS
SW3
AD8361
SW2
A
C3
100pF
B
C1
100pF
RFIN
1 VPOS
SREF 8
2 IREF
VRMS 7
VPOS
A
FLTR 6
R4
0⍀
R5
VPOS
(OPEN)
C4
VPOS
R5
6
OPEN
OPEN
2 COMM
RFIN
5
PWDN
4
TP2 VPOS
J1
3
FLTR
C1
100pF
R2
75⍀
C5
1nF
(OPEN)
TP1
COMM 5
J3
1
SW1
TP1
3
2
R7
50⍀
A
B
C4
Vrms
1nF
4 PWDN
C2
0.01␮F
AD8361
VRMS
1
B
C5
3 RFIN
R2
75⍀
J2
R4
0⍀
SW1
Figure 43. Evaluation Board Schematic micro_SOIC
Figure 46. Evaluation Board Schematic, SOT-23-6L
Figure 44. Layout of Component Side micro_SOIC
Figure 47. Layout of the Component Side, SOT-23-6L
Figure 45. Silkscreen of Component Side micro_SOIC
Figure 48. Silkscreen of the Component Side, SOT-23-6L
REV. A
–15–
Problems caused by impedance mismatch may arise using the
evaluation board to examine the AD8361 performance. One
way to reduce these problems is to put a coaxial 3 dB attenuator
on the RFIN SMA connector. Mismatches at the source, cable,
and cable interconnection, as well as those occurring on the
evaluation board can cause these problems.
A simple (and common) example of such problem is triple travel
due to mismatch at both the source and the evaluation board.
Here the signal from the source reaches the evaluation board
and mismatch causes a reflection. When that reflection reaches
the source mismatch, it causes a new reflection, which travels
back to the evaluation board adding to the original signal incident at the board. The resultant voltage will vary with both
cable length and frequency dependent upon the relative phase of
the initial and reflected signals. Placing the 3 dB pad at the
input of the board improves the match at the board and thus
reduces the sensitivity to mismatches at the source. When such
precautions are taken, measurements will be less sensitive to
cable length and other fixturing issues. In an actual application
when the distance between AD8361 and source is short and well
defined, this 3 dB attenuator is not needed.
The Error from Linear Response to CW waveform is the difference
in output from the ideal output defined by the conversion gain
and output reference. This is a measure of both the linearity of
the device response to both CW and modulated waveforms. The
error in dB uses the conversion gain multiplied times the input
as its reference. Error from Linear Response to CW waveform is not a
measure of absolute accuracy, since it is calculated using the
gain and output reference of each device. But it does show the
linearity and effect of modulation on the device response.
Error from 25°C performance uses the performance of a given
device and waveform type as the reference; it is predominantly a measure of output variation with temperature.
CHARACTERIZATION SETUPS
Equipment
C4
0.1␮F
C2
100pF
C3716a–2–6/00 (rev. A) 01088
AD8361
AD8361
VPOS
1
VPOS
SREF 8
IREF
2
IREF
VRMS 7
RFIN
3
RFIN
FLTR 6
4
PWDN
SREF
VRMS
C3
R1
75⍀
C1
0.1␮F
COMM 5
PWDN
Figure 49. Characterization Board
The primary characterization setup is shown in Figure 50. The
signal source used was a Rohde & Schwarz SMIQ03B, version
3.90HX. The modulated waveforms used for IS95 reverse link,
IS95 nine active channels forward (Forward Link 18 setting),
W-CDMA 4- and 15-channel were generated using the default
settings coding and filtering. Signal levels were calibrated into a
50 Ω impedance.
AD8361
CHARACTERIZATION
BOARD
DC OUTPUT
RF SIGNAL
SMIQ038B
RF SOURCE
VRMS
RFIN
3dB
ATTENUATOR
PRUP
Analysis
The conversion gain and output reference are derived using the
coefficients of a linear regression performed on data collected in
its central operating range (35 mV rms to 250 mV rms). This
range was chosen to avoid areas of operation where offset distorts
the linear response. Error is stated in two forms Error from Linear
Response to CW waveform and Output Delta from 25°C performance.
+VS
SREF
IREF
DC SOURCES
IEEE BUS
DC MATRIX / DC SUPPLIES / DMM
PC CONTROLLER
Figure 50. Characterization Setup
OUTLINE DIMENSIONS
8-Lead micro_SOIC Package
(RM-8)
6-Lead SOT-23-6L Package
(RT-6)
0.122 (3.10)
0.114 (2.90)
0.122 (3.10)
0.106 (2.70)
8
5
0.071 (1.80)
0.059 (1.50)
0.193
(4.90)
BSC
0.122 (3.10)
0.114 (2.90)
1
6
5
4
1
2
3
PRINTED IN U.S.A.
Dimensions shown in inches and (mm).
0.118 (3.00)
0.098 (2.50)
4
PIN 1
PIN 1
0.0256 (0.65) BSC
0.006 (0.15)
0.002 (0.05)
0.016 (0.40)
0.010 (0.25)
0.043
(1.10)
MAX
6ⴗ
0ⴗ
SEATING
0.009
(0.23)
PLANE
0.005 (0.13)
0.037 (0.95) BSC
0.037 (0.95)
0.030 (0.75)
0.075 (1.90)
BSC
0.051 (1.30)
0.035 (0.90)
0.028 (0.70)
0.016 (0.40)
0.006 (0.15)
0.000 (0.00)
–16–
0.057 (1.45)
0.035 (0.90)
0.020 (0.50) SEATING
0.010 (0.25) PLANE
10ⴗ
0.009 (0.23) 0ⴗ
0.003 (0.08)
0.022 (0.55)
0.014 (0.35)
REV. A