Wide bandwidth: 1 MHz to 10 GHz
High accuracy: ±1.0 dB over temperature
55 dB dynamic range up to 8 GHz ± 3 dB error
Stability over temperature: ±0.5 dB
Low noise measurement/controller output, VOUT
Pulse response time: 6 ns/10 ns (fall/rise)
Small footprint, 2 mm × 3 mm LFCSP
Supply operation: 3.0 V to 5.5 V @ 22 mA
Fabricated using high speed SiGe process
APPLICATIONS
RF transmitter PA setpoint control and level monitoring
Power monitoring in radio link transmitters
RSSI measurement in base stations, WLANs, WiMAX, and radars
GENERAL DESCRIPTION
The AD8317 is a demodulating logarithmic amplifier, capable
of accurately converting an RF input signal to a corresponding
decibel-scaled output. It employs the progressive compression
technique over a cascaded amplifier chain, each stage of which
is equipped with a detector cell. The device can be used in either
measurement or controller modes. The AD8317 maintains
accurate log conformance for signals of 1 MHz to 8 GHz and
provides useful operation to 10 GHz. The input dynamic range
is typically 55 dB (re: 50 ) with less than ±3 dB error. The
AD8317 has 6 ns/10 ns response time (fall time/rise time) that
enables RF burst detection to a pulse rate of beyond 50 MHz.
The device provides unprecedented logarithmic intercept stability
vs. ambient temperature conditions. A supply of 3.0 V to 5.5 V
is required to power the device. Current consumption is typically
22 mA, and it decreases to 200 µA when the device is disabled.
The AD8317 can be configured to provide a control voltage to a
power amplifier or a measurement output from the VOUT pin.
Because the output can be used for controller applications, special
attention has been paid to minimize wideband noise. In this
mode, the setpoint control voltage is applied to the VSET pin.
Log Detector/Controller
AD8317
FUNCTIONAL BLOCK DIAGRAM
POS
GAIN
BIAS
DETDETDETDET
INHI
INLO
The feedback loop through an RF amplifier is closed via VOUT,
the output of which regulates the output of the amplifier to a
magnitude corresponding to V
(V
− 0.1 V) output capability at the VOUT pin, suitable for
POS
controller applications. As a measurement device, VOUT is
externally connected to VSET to produce an output voltage,
V
, that is a decreasing linear-in-dB function of the RF input
OUT
signal amplitude.
The logarithmic slope is −22 mV/dB, determined by the VSET
interface. The intercept is 15 dBm (re: 50 Ω, CW input) using
the INHI input. These parameters are very stable against supply
and temperature variations.
The AD8317 is fabricated on a SiGe bipolar IC process and is
available in a 2 mm × 3 mm, 8-lead LFCSP with an operating
temperature range of −40°C to +85°C.
TADJ
SLOPE
COMM
Figure 1.
. The AD8317 provides 0 V to
SET
IV
IV
VSET
CLPF
05541-001
Rev. B
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 that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarks and registered trademarks are the property of their respective owners.
Specified Frequency Range 0.001 10 GHz
DC Common-Mode Voltage V
MEASUREMENT MODE
f = 900 MHz R
Input Impedance 1500||0.33 Ω||pF
±1 dB Dynamic Range TA = 25°C 50 dB
−40°C < TA < +85°C 46 dB
Maximum Input Level ±1 dB error −3 dBm
Minimum Input Level ±1 dB error −53 dBm
Slope
Intercept
Output Voltage, High Power In PIN = −10 dBm 0.42 0.58 0.78 V
Output Voltage, Low Power In PIN = −40 dBm 1.00 1.27 1.40 V
f = 1.9 GHz R
Input Impedance 950||0.38 Ω||pF
±1 dB Dynamic Range TA = 25°C 50 dB
−40°C < TA < +85°C 48 dB
Maximum Input Level ±1 dB error −4.00 dBm
Minimum Input Level ±1 dB error −54 dBm
Slope
Intercept
Output Voltage, High Power In PIN = −10 dBm 0.35 0.54 0.80 V
Output Voltage, Low Power In PIN = −35 dBm 0.75 1.21 1.35 V
f = 2.2 GHz R
Input Impedance 810||0.39 Ω||pF
±1 dB Dynamic Range TA = 25°C 50 dB
−40°C < TA < +85°C 47 dB
Maximum Input Level ±1 dB error −5 dBm
Minimum Input Level ±1 dB error −55 dBm
Slope
Intercept
Output Voltage, High Power In PIN = −10 dBm 0.53 V
Output Voltage, Low Power In PIN = −40 dBm 1.20 V
f = 3.6 GHz R
Input Impedance 300||0.33 Ω||pF
±1 dB Dynamic Range TA = 25°C 42 dB
−40°C < TA < +85°C 40 dB
Maximum Input Level ±1 dB error −6 dBm
Minimum Input Level ±1 dB error −48 dBm
Slope
Intercept
Output Voltage, High Power In PIN = −10 dBm 0.47 V
Output Voltage, Low Power In PIN = −40 dBm 1.16 V
= 1000 pF, TA = 25°C, 52.3 Ω termination resistor at INHI, unless otherwise noted.
LPF
− 0.6 V
POS
VOUT (Pin 5) shorted to VSET (Pin 4), sinusoidal
input signal
= 18 kΩ
TAD J
1
−25 −22 −19.5 mV/dB
1
12 15 21 dBm
= 8 kΩ
TAD J
1
−25 −22 −19.5 mV/dB
1
10 14 20 dBm
= 8 kΩ
TAD J
1
−22 mV/dB
1
14 dBm
= 8 kΩ
TAD J
1
−22 mV/dB
1
11 dBm
Rev. B | Page 3 of 20
AD8317
Parameter Conditions Min Typ Max Unit
f = 5.8 GHz R
Input Impedance 110||0.05 Ω||pF
±1 dB Dynamic Range TA = 25°C 50 dB
−40°C < TA < +85°C 48 dB
Maximum Input Level ±1 dB error −4 dBm
Minimum Input Level ±1 dB error −54 dBm
1
Slope
−22 mV/dB
Intercept
1
16 dBm
Output Voltage, High Power In PIN = −10 dBm 0.59 V
Output Voltage, Low Power In PIN = −40 dBm 1.27 V
f = 8.0 GHz R
Input Impedance 28||0.79 Ω||pF
±1 dB Dynamic Range TA = 25°C 44 dB
−40°C < TA < +85°C 35 dB
Maximum Input Level ±1 dB error −2 dBm
Minimum Input Level ±1 dB error −46 dBm
2
Slope
−22 mV/dB
Intercept
2
21 dBm
Output Voltage, High Power In PIN = −10 dBm 0.70 V
Output Voltage, Low Power In PIN = −40 dBm 1.39 V
OUTPUT INTERFACE VOUT (Pin 5)
Voltage Swing V
V
Output Current Drive V
Small Signal Bandwidth RFIN = −10 dBm, from CLPF to VOUT 140 MHz
Output Noise
Fall Time
Rise Time
Video Bandwidth (or Envelope Bandwidth) 50 MHz
VSET INTERFACE VSET (Pin 4)
Nominal Input Range RFIN = 0 dBm, measurement mode 0.35 V
RFIN = −50 dBm, measurement mode 1.40 V
Logarithmic Scale Factor −45 dB/V
Input Resistance RFIN = −20 dBm, controller mode, V
TAD J INTERFACE TADJ ( Pin 6)
Input Resistance TADJ = 0.9 V, sourcing 50 A 13 kΩ
Disable Threshold Voltage TADJ = open V
POWER INTERFACE VPOS (Pin 7)
Supply Voltage 3.0 5.5 V
Quiescent Current 18 22 30 mA
vs. Temperature −40°C ≤ TA ≤ +85°C 60 µA/°C
Disable Current TADJ = V
1
Slope and intercept are determined by calculating the best-fit line between the power levels of −40 dBm and −10 dBm at the specified input frequency.
2
Slope and intercept are determined by calculating the best-fit line between the power levels of −34 dBm and −16 dBm at 8.0 GHz.
= 500 Ω
TAD J
= open
TAD J
= 0 V, RFIN = open V
SET
= 1.7 V, RFIN = open 10 mV
SET
= 0 V, RFIN = open 10 mA
SET
RFIN = 2.2 GHz, −10 dBm, f
= open
C
LPF
= 100 kHz,
NOISE
Input level = no signal to −10 dBm, 90% to 10%,
C
= 8 pF
LPF
Input level = no signal to −10 dBm, 90% to 10%,
= open, R
C
LPF
= 150 Ω
OUT
Input level = −10 dBm to no signal, 10% to 90%,
= 8 pF
C
LPF
Input level = −10 dBm to no signal, 10% to 90%,
C
= open, R
LPF
= 150 Ω
OUT
= 1 V 40 kΩ
SET
200 µA
POS
90 nV/√Hz
18 ns
6 ns
20 ns
10 ns
− 0.1 V
POS
− 0.4 V
POS
Rev. B | Page 4 of 20
AD8317
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter Rating
Supply Voltage, V
V
Voltage 0 V to V
SET
Input Power (Single-Ended, Re: 50 Ω) 12 dBm
Internal Power Dissipation 0.73 W
θJA 55°C/W
Maximum Junction Temperature 125°C
Operating Temperature Range −40°C to +85°C
Storage Temperature Range −65°C to +150°C
Lead Temperature (Soldering, 60 sec) 260°C
5.7 V
POS
POS
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.
ESD CAUTION
Rev. B | Page 5 of 20
AD8317
C
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
1INHI
OMM
2
AD8317
TOP VIEW
3CLPF
(Not to Scale)
4VSET
Figure 2. Pin Configuration
8INLO
7VPOS
6TADJ
5VOUT
05541-002
Table 3. Pin Function Descriptions
Pin No. Mnemonic Description
1 INHI RF Input. Nominal input range of −50 dBm to 0 dBm, re: 50 Ω; ac-coupled RF input.
2 COMM Device Common. Connect to a low impedance ground plane.
3 CLPF
Loop Filter Capacitor. In measurement mode, this capacitor sets the pulse response time and video bandwidth.
In controller mode, the capacitance on this node sets the response time of the error amplifier/integrator.
4 VSET Setpoint Control Input for Controller Mode or Feedback Input for Measurement Mode.
5 VOUT
Measurement and Controller Output. In measurement mode, VOUT provides a decreasing linear-in-dB
representation of the RF input signal amplitude. In controller mode, VOUT is used to control the gain of a VGA or
VVA with a positive gain sense (increasing voltage increases gain).
6 TADJ
Temperature Compensation Adjustment. Frequency-dependent temperature compensation is set by connecting
a ground-referenced resistor to this pin.
7 VPOS Positive Supply Voltage: 3.0 V to 5.5 V.
8 INLO RF Common for INHI. AC-coupled RF common.
Paddle Internally connected to COMM; solder to a low impedance ground plane.
Figure 19. Noise Spectral Density of Output Buffer (from CLPF to VOUT);
= 0.1 μF
C
LPF
2.00
1.75
1.50
1.25
(V)
1.00
OUT
V
0.75
0.50
3.3V
0.25
3.0V
3.6V
0
–55–45–35–25–15–5515
–65
P
(dBm)
IN
2.0
1.5
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
ERROR (d B)
05541-020
Figure 20. Output Voltage Stability vs. Supply Voltage at 1.9 GHz
When V
Varies by 10%
POS
Rev. B | Page 9 of 20
AD8317
VOUT
V
THEORY OF OPERATION
The AD8317 is a 6-stage demodulating logarithmic amplifier,
specifically designed for use in RF measurement and power
control applications at frequencies up to 10 GHz. A block
diagram is shown in Figure 21. Sharing much of its design
with the AD8318 logarithmic detector/controller, the AD8317
maintains tight intercept variability vs. temperature over a 50 dB
range. Additional enhancements over the AD8318, such as a
reduced RF burst response time of 6 ns to 10 ns, 22 mA supply
current, and board space requirements of only 2 mm × 3 mm,
add to the low cost and high performance benefits of the AD8317.
TADJ
SLOPE
COMM
IV
IV
VSET
CLPF
INHI
INLO
POS
GAIN
BIAS
DETDETDETDET
Figure 21. Block Diagram
A fully differential design, using a proprietary, high speed SiGe
process, extends high frequency performance. Input INHI receives
the signal with a low frequency impedance of nominally 500 Ω
in parallel with 0.7 pF. The maximum input with ±1 dB logconformance error is typically 0 dBm (re: 50 Ω). The noise
spectral density referred to the input is 1.15 nV/√Hz, which is
equivalent to a voltage of 118 µV rms in a 10.5 GHz bandwidth
or a noise power of −66 dBm (re: 50 Ω). This noise spectral
density sets the lower limit of the dynamic range. However,
the low end accuracy of the AD8317 is enhanced by specially
shaping the demodulating transfer characteristic to partially
05541-021
compensate for errors due to internal noise. The common pin,
COMM, provides a quality low impedance connection to the
printed circuit board (PCB) ground. The package paddle, which
is internally connected to the COMM pin, should also be grounded
to the PCB to reduce thermal impedance from the die to the PCB.
The logarithmic function is approximated in a piecewise fashion
by six cascaded gain stages. (For a more comprehensive explanation of the logarithm approximation, see the AD8307 data
sheet.) The cells have a nominal voltage gain of 9 dB each and a
3 dB bandwidth of 10.5 GHz. Using precision biasing, the gain
is stabilized over temperature and supply variations. The overall
dc gain is high, due to the cascaded nature of the gain stages. An
offset compensation loop is included to correct for offsets
within the cascaded cells. At the output of each of the gain
stages, a square-law detector cell is used to rectify the signal.
The RF signal voltages are converted to a fluctuating differential
current having an average value that increases with signal level.
Along with the six gain stages and detector cells, an additional
detector is included at the input of the AD8317, providing a
50 dB dynamic range in total. After the detector currents are
summed and filtered, the following function is formed at the
summing node:
I
× log10(VIN/V
D
) (1)
INTERCEPT
where:
I
is the internally set detector current.
D
is the input signal voltage.
V
IN
V
is the intercept voltage (that is, when VIN = V
INTERCEPT
INTERCEPT
,
the output voltage would be 0 V, if it were capable of going to 0 V).
Rev. B | Page 10 of 20
AD8317
V
V
VOUT
V
C
V
USING THE AD8317
BASIC CONNECTIONS
The AD8317 is specified for operation up to 10 GHz; as a result,
low impedance supply pins with adequate isolation between
functions are essential. A power supply voltage of between 3.0 V
and 5.5 V should be applied to VPOS. Power supply decoupling
capacitors of 100 pF and 0.1 µF should be connected close to
this power supply pin.
(3.0VTO 5.5V)
S
C5
0.1µF
R2
0Ω
C4
C2
47nF
R1
52.3Ω
SIGNAL
INPUT
1
SEE THE TEMPERATURE COMPENSATION OF OUTPUT VOLTAGE SECTION.
2
SEE THE OUTPUT FILTERING SECTION.
C1
47nF
100pF
8765
INLO VPOSTADJ VOUT
AD8317
INHI
COMM CLPF VSET
1234
1
2
V
OUT
R4
0Ω
Figure 22. Basic Connections
The paddle of the LFCSP package is internally connected to
COMM. For optimum thermal and electrical performance, the
paddle should be soldered to a low impedance ground plane.
INPUT SIGNAL COUPLING
The RF input (INHI) is single-ended and must be ac-coupled.
INLO (input common) should be ac-coupled to ground.
Suggested coupling capacitors are 47 nF ceramic 0402-style
capacitors for input frequencies of 1 MHz to 10 GHz. The
coupling capacitors should be mounted close to the INHI and
INLO pins. The coupling capacitor values can be increased to
lower the high-pass cutoff frequency of the input stage. The
high-pass corner is set by the input coupling capacitors and the
internal 10 pF high-pass capacitor. The dc voltage on INHI and
INLO is approximately one diode voltage drop below V
POS
5pF5pF
18.7kΩ18.7kΩ
INHI
INLO
CURRENT
2kΩ
gm
STAGE
Figure 23. Input Interface
FIRST
GAIN
STAGE
A = 9dB
OFFSET
COMP
While the input can be reactively matched, in general, this is not
necessary. An external 52.3 Ω shunt resistor (connected on the
signal side of the input coupling capacitors, as shown in
.
POS
05541-023
Rev. B | Page 11 of 20
05541-022
Figure 22) combines with the relatively high input impedance to
give an adequate broadband 50 Ω match.
The coupling time constant, 50 × C
corner with a 3 dB attenuation at f
C1 = C2 = C
. Using the typical value of 47 nF, this high-pass
C
corner is ~68 kHz. In high frequency applications, f
/2, forms a high-pass
C
= 1/(2π × 50 × CC ), where
HP
should be
HP
as large as possible to minimize the coupling of unwanted low
frequency signals. In low frequency applications, a simple RC
network forming a low-pass filter should be added at the input
for similar reasons. This low-pass filter network should generally
be placed at the generator side of the coupling capacitors, thereby
lowering the required capacitance value for a given high-pass
corner frequency.
OUTPUT INTERFACE
The VOUT pin is driven by a PNP output stage. An internal
10 Ω resistor is placed in series with the output and the VOUT
pin. The rise time of the output is limited mainly by the slew
on CLPF. The fall time is an RC-limited slew given by the load
capacitance and the pull-down resistance at VOUT. There is an
internal pull-down resistor of 1.6 kΩ. A resistive load at VOUT
is placed in parallel with the internal pull-down resistor to
provide additional discharge current.
POS
CLPF
OMM
0.8V
+
–
10Ω
1200Ω
400Ω
05541-024
Figure 24. Output Interface
To reduce the fall time, VOUT should be loaded with a resistive
load of <1.6 kΩ. For example, with an external load of 150 Ω,
the AD8317 fall time is <7 ns.
SETPOINT INTERFACE
The V
internal op amp. The V
1.5 kΩ resistor to generate I
applied to VSET, the feedback loop forces
If V
The result is
input drives the high impedance (40 kΩ) input of an
SET
voltage appears across the internal
SET
. When a portion of V
SET
−I
× log10(VIN/V
D
= V
SET
V
/2x, then I
OUT
= (−ID × 1.5 kΩ × 2x) × log10(VIN/V
OUT
SET
INTERCEPT
= V
SET
20kΩ
20kΩ
) = I
SET
/(2x × 1.5 kΩ).
OUT
V
SET
COMM
(2)
INTERCEPT
I
SET
1.5kΩ
COMM
05541-025
Figure 25. VSET Interface
is
OUT
)
AD8317
The slope is given by
× 2x × 1.5 kΩ = −22 mV/dB × x
−I
D
For example, if a resistor divider to ground is used to generate a
V
voltage of V
SET
/2, x = 2. The slope is set to −880 V/decade
OUT
or −44 mV/dB.
TEMPERATURE COMPENSATION OF OUTPUT
VOLTAGE
The primary component of the variation in V
as the input signal amplitude is held constant, is the drift of the
intercept. This drift is also a weak function of the input signal
frequency; therefore, provision is made for the optimization of
internal temperature compensation at a given frequency by
providing Pin TADJ.
V
INTERNAL
TADJ
R
TADJ
1.5k
COMMCOMM
Figure 26. TADJ Interface
R
is connected between TADJ and ground. The value of
TAD J
this resistor partially determines the magnitude of an analog
correction coefficient, which is used to reduce intercept drift.
The relationship between output temperature drift and
frequency is not linear and cannot be easily modeled. As a
result, experimentation is required to choose the correct
TADJ resistor. Ta b l e 4 shows the recommended values for
some commonly used frequencies.
Table 4. Recommended R
TADJ
Values
Frequency Recommended R
50 MHz 18 kΩ
100 MHz 18 kΩ
900 MHz 18 kΩ
1.8 GHz 8 kΩ
1.9 GHz 8 kΩ
2.2 GHz 8 kΩ
3.6 GHz 8 kΩ
5.3 GHZ 500 Ω
5.8 GHz 500 Ω
8 GHz Open
OUT
AD8317
I
COMP
Ω
TAD J
vs. temperature,
05541-026
MEASUREMENT MODE
When the V
back to the VSET pin, the device operates in measurement
mode. As seen in Figure 27, the AD8317 has an offset voltage,
a negative slope, and a V
end of its input signal range.
Figure 27. Typical Output Voltage vs. Input Signal
The output voltage vs. input signal voltage of the AD8317 is
linear-in-dB over a multidecade range. The equation for this
function is
V
= X × V
OUT
= X × V
SLOPE/dB
× log10(VIN/V
SLOPE/DEC
× 20 × log10(VIN/V
) (3)
INTERCEPT
) (4)
INTERCEPT
where:
X is the feedback factor in V
V
V
the V
V
An offset voltage, V
is nominally −440 mV/decade, or −22 mV/dB.
SLOPE/DEC
is the x-axis intercept of the linear-in-dB portion of
INTERCEPT
vs. PIN curve (see Figure 27).
OUT
is 2 dBV for a sinusoidal input signal.
INTERCEPT
OFFSET
the detector signal, so that the minimum value for V
X × V
; therefore, for X = 1, the minimum V
OFFSET
= V
OUT
/X.
SET
, of 0.35 V is internally added to
is
OUT
is 0.35 V.
OUT
The slope is very stable vs. process and temperature variation.
When base-10 logarithms are used, V
SLOPE/DECADE
volts/decade. A decade corresponds to 20 dB; V
V
represents the slope in volts/dB.
SLOPE/dB
As noted in Equation 3 and Equation 4, the V
represents the
SLOPE/DECADE
voltage has a
OUT
/20 =
negative slope. This is also the correct slope polarity to control
the gain of many power amplifiers in a negative feedback configuration. Because both the slope and intercept vary slightly
with frequency, it is recommended to refer to the Specifications
section for application-specific values for slope and intercept.
Although demodulating log amps respond to input signal
voltage, not input signal power, it is customary to discuss the
amplitude of high frequency signals in terms of power. In this
case, the characteristic impedance of the system, Z
, must be
0
known to convert voltages to their corresponding power levels.
The following equations are used to perform this conversion:
P [dBm] = 10 × log
P [dBV] = 20 × log
P [dBm] = P [dBV] − 10 × log
2
/(Z0 × 1 mW)) (5)
10(VRMS
/1 V
10(VRMS
) (6)
RMS
× 1 mW/1 V
10(Z0
2
) (7)
RMS
05541-027
Rev. B | Page 12 of 20
AD8317
For example, P
for a sinusoidal input signal expressed in
INTERCEPT
terms of dBm (decibels referred to 1 mW), in a 50 Ω system is
P
P
2 dBV − 10 × log
[dBm] =
INTERCEPT
[dBV] − 10 × log10(Z0 × 1 mW/1 V
INTERCEPT
(50 × 10−3) = 15 dBm (8)
10
RMS
2
) =
For a square wave input signal in a 200 Ω system,
P
−1 dBV − 10 × log
INTERCEPT
=
[(200 Ω × 1 mW/1 V
10
2
)] = 6 dBm
RMS
Further information on the intercept variation dependence
upon waveform can be found in the AD8313 and AD8307
data sheets.
SETTING THE OUTPUT SLOPE IN MEASUREMENT
MODE
To operate in measurement mode, VOUT must be connected
to VSET. Connecting VOUT directly to VSET yields the nominal
logarithmic slope of approximately −22 mV/dB. The output
swing corresponding to the specified input range is then approximately 0.35 V to 1.7 V. The slope and output swing can be
increased by placing a resistor divider between VOUT and
VSET (that is, one resistor from VOUT to VSET and one
resistor from VSET to ground). The input impedance of VSET
is approximately 40 kΩ. Slope-setting resistors should be kept
below 20 kΩ to prevent this input impedance from affecting
the resulting slope. If two equal resistors are used (for example,
10 kΩ/10 kΩ), the slope doubles to approximately −44 mV/dB.
AD8317
VOUT
VSET
Figure 28. Increasing the Slope
10kΩ
10kΩ
–44mV/dB
05541-028
CONTROLLER MODE
The AD8317 provides a controller mode feature at the VOUT
pin. By using V
AD8317 to control subsystems, such as power amplifiers (PAs),
variable gain amplifiers (VGAs), or variable voltage attenuators
(VVAs), that have output power that increases monotonically
with respect to their gain control signal.
To operate in controller mode, the link between VSET and
VOUT is broken. A setpoint voltage is applied to the VSET
input, VOUT is connected to the gain control terminal of the
VGA, and the RF input of the detector is connected to the
output of the VGA (usually using a directional coupler and
some additional attenuation). Based on the defined relationship
for the setpoint voltage, it is possible for the
SET
between V
and the RF input signal when the device is in
OUT
measurement mode, the AD8317 adjusts the voltage on VOUT
(VOUT is now an error amplifier output) until the level at the
RF input corresponds to the applied V
. When the AD8317
SET
operates in controller mode, there is no defined relationship
between the V
and the V
SET
voltage; V
OUT
settles to a value
OUT
that results in the correct input signal level appearing at
INHI/INLO.
For this output power control loop to be stable, a groundreferenced capacitor must be connected to the CLPF pin. This
capacitor, C
, integrates the error signal (in the form of a
FLT
current) to set the loop bandwidth and ensure loop stability.
Further details on control loop dynamics can be found in the
AD8315 data sheet.
DIRECTIONA L
COUPLER
ATT ENU ATOR
47nF
INHI
52.3Ω
INLO
47nF
Figure 29. Controller Mode
Decreasing V
, which corresponds to demanding a higher
SET
signal from the VGA, increases V
VGA/VVA
GAIN
CONTROL
VOLTAGE
VOUT
AD8317
VSET
CLPF
C
. The gain control voltage
OUT
FLT
RFIN
DAC
05541-029
of the VGA must have a positive sense. A positive control
voltage to the VGA increases the gain of the device.
The basic connections for operating the AD8317 in an automatic gain control (AGC) loop with the ADL5330 are shown in
Figure 30. The ADL5330 is a 10 MHz to 3 GHz VGA. It offers a
large gain control range of 60 dB with ±0.5 dB gain stability.
This configuration is similar to Figure 29.
The gain of the ADL5330 is controlled by the output pin of the
AD8317. This voltage, V
, has a range of 0 V to near V
OUT
POS
. To
avoid overdrive recovery issues, the AD8317 output voltage can
be scaled down using a resistive divider to interface with the 0 V
to 1.4 V gain control range of the ADL5330.
A coupler/attenuation of 21 dB is used to match the desired
maximum output power from the VGA to the top end of the
linear operating range of the AD8317 (approximately −5 dBm
at 900 MHz).
Rev. B | Page 13 of 20
AD8317
V
V
RF INPUT
SIGNAL
100pF
+5
VPSxCOMx
INHI
OPHI
ADL5330
OPLO
GAIN
10kΩ
VOUTVPOS
AD8317
LOG AMP
TADJ
DAC
1nF
100pF
SETPOINT
VOLTAGE
INLO
4.12kΩ
VSETINHI
18kΩ
Figure 30. AD8317 Operating in Controller Mode to Provide Automatic Gain Control Functionality in Combination with the ADL5330
Figure 31 shows the transfer function of the output power vs.
the setpoint voltage over temperature for a 900 MHz sine wave
with an input power of −1.5 dBm. Note that the power control
of the AD8317 has a negative sense. Decreasing V
, which
SET
corresponds to demanding a higher signal from the ADL5330,
increases gain.
The AGC loop is capable of controlling signals just under the
full 60 dB gain control range of the ADL5330. The performance
over temperature is most accurate over the highest power range,
where it is generally most critical. Across the top 40 dB range
of output power, the linear conformance error is well within
±0.5 dB over temperature.
30
20
10
4
3
2
+5V
COMM
+5
RF OUTPUT
120nH
INLOCLPF
47nF
47nF
120nH
100pF
100pF
52.3Ω
DIRECTIO NAL
COUPLER
ATT ENU ATOR
SIGNAL
05541-030
For the AGC loop to remain in equilibrium, the AD8317 must
track the envelope of the ADL5330 output signal and provide
the necessary voltage levels to the ADL5330 gain control input.
Figure 32 shows an oscilloscope screenshot of the AGC loop
depicted in Figure 30. A 100 MHz sine wave with 50% AM
modulation is applied to the ADL5330. The output signal from
the VGA is a constant envelope sine wave with amplitude corresponding to a setpoint voltage at the AD8317 of 1.5 V. Also
shown is the gain control response of the AD8317 to the
changing input envelope.
AM MODULATED INPUT
1
AD8317 OUTPUT
0
–10
–20
OUTPUT POWER (dBm)
–30
–40
–50
0.20. 40.60.8 1.01.41.8
SETPOINT VOLTAGE (V)
1.61.2
Figure 31. ADL5330 Output Power vs. AD8317 Setpoint Voltage, P
1
0
–1
–2
–3
–4
0
.
2
= −1.5 dBm
IN
ERROR (dB)
3
ADL5330 OUTPUT
2
CH1 200mV
CH3 50.0mVΩ
Ch2 200mV
M2.00ms
T 640.00µs
A CH2 820mV
05541-032
Figure 32. Oscilloscope Screenshot Showing an AM Modulated Input Signal
and the Response from the AD8317
05541-031
Rev. B | Page 14 of 20
AD8317
Figure 33 shows the response of the AGC RF output to a pulse
on VSET. As V
decreases from 1.7 V to 0.4 V, the AGC loop
SET
responds with an RF burst. In this configuration, the input
signal to the ADL5330 is a 1 GHz sine wave at a power level
of −15 dBm.
T
AD8317 VSET PULSE
I
LOG
1.5kΩ
3.5pF
AD8317
+4
VOUT
CLPF
C
FLT
05541-037
1
ADL5330 OUTPUT
2
CH2 50mVΩ
M10.0µsCH1 2.00V
T 699.800µs
A CH1 2.48V
05541-033
Figure 33. Oscilloscope Screenshot Showing
the Response Time of the AGC Loop
Response time and the amount of signal integration are controlled by C
. This functionality is analogous to the feedback
FLT
capacitor around an integrating amplifier. Although it is
possible to use large capacitors for C
, in most applications,
FLT
values under 1 nF provide sufficient filtering.
Calibration in controller mode is similar to the method used
in measurement mode. A simple 2-point calibration can be
done by applying two known V
voltages or DAC codes and
SET
measuring the output power from the VGA. Slope and intercept
can then be calculated by:
− V
)/(P
− P
Slope = (V
SET1
Intercept = P
V
= Slope × (P
SETx
OUT1
SET2
OUT1
− V
/Slope (10)
SET1
− Intercept) (11)
OUTX
) (9)
OUT2
More information on the use of the ADL5330 in AGC applications can be found in the ADL5330 data sheet.
OUTPUT FILTERING
For applications in which maximum video bandwidth and,
consequently, fast rise time are desired, it is essential that the
CLPF pin be left unconnected and free of any stray capacitance.
The nominal output video bandwidth of 50 MHz can be reduced
by connecting a ground-referenced capacitor (C
pin, as shown in Figure 34. This is generally done to reduce
output ripple (at twice the input frequency for a symmetric
input waveform such as sinusoidal signals).
) to the CLPF
FLT
Rev. B | Page 15 of 20
Figure 34. Lowering the Postdemodulation Bandwidth
C
is selected by
FLT
=
C
FLT
π
1
××
BandwidthVideo
pF5.3
−
)k5.12(
(12)
The video bandwidth should typically be set to a frequency
equal to about one-tenth the minimum input frequency. This
ensures that the output ripple of the demodulated log output,
which is at twice the input frequency, is well filtered.
In many log amp applications, it may be necessary to lower
the corner frequency of the postdemodulation filter to achieve
low output ripple while maintaining a rapid response time to
changes in signal level. An example of a 4-pole active filter is
shown in the AD8307 data sheet.
OPERATION BEYOND 8 GHz
The AD8317 is specified for operation up to 8 GHz, but it provides
useful measurement accuracy over a reduced dynamic range of
up to 10 GHz. Figure 35 shows the performance of the AD8317
over temperature at 10 GHz when the device is configured as
shown in Figure 22. Dynamic range is reduced at this frequency,
but the AD8317 does provide 30 dB of measurement range
within ±3 dB of linearity error.
2.0
1.8
1.6
1.4
1.2
(V)
1.0
OUT
V
0.8
0.6
0.4
0.2
0
–40 –35–30–25–20 –15–10–505
Figure 35. V
and Log Conformance vs. Input Amplitude at 10.0 GHz,
OUT
Multiple Devices, R
P
(dBm)
IN
TADJ
= Open, C
= 1000 pF
LPF
Implementing an impedance match for frequencies beyond
8 GHz can improve the sensitivity of the AD8317 and measurement range.
Operation beyond 10 GHz is possible, but part-to-part
variation, most notably in the intercept, becomes significant.
5
4
3
2
1
0
–1
ERROR (dB)
–2
–3
–4
–5
05541-038
AD8317
V
T
EVALUATION BOARD
Table 5. Evaluation Board (Rev. A) Configuration Options
Component Function Default Conditions
VPOS, GND Supply and Ground Connections. Not applicable
R1, C1, C2
R5, R7
R2, R3, R4, R6, RL, CL
R2, R3
C4, C5
C3
Input Interface.
The 52.3 Ω resistor in Position R1 combines with the internal input impedance
of the AD8317 to give a broadband input impedance of about 50 Ω. C1 and C2
are dc-blocking capacitors. A reactive impedance match can be implemented
by replacing R1 with an inductor and C1 and C2 with appropriately valued
capacitors.
Temperature Compensation Interface.
The internal temperature compensation network is optimized for input signals
up to 3.6 GHz when R7 is 10 kΩ. This circuit can be adjusted to optimize
performance for other input frequencies by changing the value of the resistor
in Position R7. See Table 4 for specific R
resistor values.
TAD J
Output Interface—Measurement Mode.
In measurement mode, a portion of the output voltage is fed back to the VSET
pin via R2. The magnitude of the slope of the VOUT output voltage response
can be increased by reducing the portion of V
that is fed back to VSET. R6
OUT
can be used as a back-terminating resistor or as part of a single-pole, low-pass
filter.
Output Interface—Controller Mode.
In this mode, R2 must be open. In controller mode, the AD8317 can control the
gain of an external component. A setpoint voltage is applied to Pin VSET, the
value of which corresponds to the desired RF input signal level applied to the
AD8317 RF input. A sample of the RF output signal from this variable gain
component is selected, typically via a directional coupler, and applied to the
AD8317 RF input. The voltage at the VOUT pin is applied to the gain control of
the variable gain element. A control voltage is applied to the VSET pin. The
magnitude of the control voltage can optionally be attenuated via the voltage
divider comprising R2 and R3, or a capacitor can be installed in Position R3 to
form a low-pass filter along with R2.
Power Supply Decoupling.
The nominal supply decoupling consists of a 100 pF filter capacitor placed
physically close to the AD8317 and a 0.1 µF capacitor placed nearer to the
power supply input pin.
Filter Capacitor.
The low-pass corner frequency of the circuit that drives the VOUT pin can be
lowered by placing a capacitor between CLPF and ground. Increasing this
capacitor increases the overall rise/fall time of the AD8317 for pulsed input
signals. See the Output Filtering section for more details.
R2 = 0 Ω (Size 0402)
R3 = open (Size 0402)
R4 = open (Size 0402)
R6 = 1 kΩ (Size 0402)
RL = CL = open (Size 0402)
R2 = open (Size 0402)
R3 = open (Size 0402)
C4 = 0.1 µF (Size 0603)
C5 = 100 pF (Size 0402)
C3 = 8.2 pF (Size 0402)
V
OU
05541-034
Figure 36. Evaluation Board Schematic
Rev. B | Page 16 of 20
AD8317
05541-036
05541-035
Figure 37. Component Side Layout
Figure 38. Component Side Silkscreen
Rev. B | Page 17 of 20
AD8317
X
DIE INFORMATION
1
2
2
ADI AD8317
3
4
DB1
BOND PAD STATI STICS
ALL MEASURMENT S IN MICRO NS.
MINIMUM PASSIVATION OPENING: 59 × 59 MIN PAD PITCH: 89
DIE SIZE CALCULATIO N
ALL MEASURMENT S IN MICRO NS.
DIEX (WIDTH OF DIE IN X DIRECTION) = 670
DIEY (WIDTH OF DIE IN Y DIRECTION) = 1325
DIE THICKNESS = 305 MICRONS
BALL BOND SHEAR ST RENGTH SPECIFICATION: MINI MUM 15 GRAMS
8
7
Y
6
5
05541-039
Figure 39. Die Outline Dimensions
Table 6. Die Pad Function Descriptions
Pin No. Mnemonic Description
1 INHI RF Input. Nominal input range of −50 dBm to 0 dBm, re: 50 Ω; ac-coupled RF input.
2, 2 COMM Device Common. Connect both pads to a low impedance ground plane.
3 CLPF
Loop Filter Capacitor. In measurement mode, this capacitor sets the pulse response time and video
bandwidth. In controller mode, the capacitance on this node sets the response time of the error
amplifier/integrator.
4 VSET Setpoint Control Input for Controller Mode or Feedback Input for Measurement Mode.
5 VOUT
Measurement and Controller Output. In measurement mode, VOUT provides a decreasing linear-in dB
representation of the RF input signal amplitude. In controller mode, VOUT is used to control the gain of
a VGA or VVA with a positive gain sense (increasing voltage increases gain).
6 TADJ
Temperature Compensation Adjustment. Frequency-dependent temperature compensation is set by
connecting a ground-referenced resistor to this pin.
7 VPOS Positive Supply Voltage: 3.0 V to 5.5 V.
8 INLO RF Common for INHI. AC-coupled RF common.
DB1 COMM Device Common. Connect to a low impedance ground plane.
Rev. B | Page 18 of 20
AD8317
C
OUTLINE DIMENSIONS
1.89
1.74
1.59
5
EXPOSEDPAD
BOTTOM VIEW
4
8
1
0.50 BSC
0.25
0.20
0.15
0.15
0.10
0.05
INDI
PIN 1
ATO R
1.95
1.75
1.55
3.25
3.00
2.75
TOP VIEW
2.95
2.75
2.55
2.25
2.00
1.75
0.60
0.45
0.30
0.55
0.40
0.30
1.00
0.85
0.80
SEATING
PLANE
12° MAX
0.30
0.23
0.18
0.80 MAX
0.65 TYP
0.20 REF
0.05 MAX
0.02 NOM
031207-A
Figure 40. 8-Lead Lead Frame Chip Scale Package [LFCSP_VD]
2 mm × 3 mm Body, Very Thin, Dual Lead
(CP-8-1)
Dimensions shown in millimeters
ORDERING GUIDE
Model Temperature Range Package Description Package Option Branding
AD8317ACPZ-R7
AD8317ACPZ-R2
AD8317ACPZ-WP
AD8317ACHIPS −40°C to +85°C Die
AD8317-EVALZ
1
Z = RoHS Compliant Part.
1
−40°C to +85°C 8-Lead LFCSP_VD, 7” Tape and Reel CP-8-1 Q1
1
−40°C to +85°C 8-Lead LFCSP_VD, 7” Tape and Reel CP-8-1 Q1
1
−40°C to +85°C 8-Lead LFCSP_VD, Waffle Pack CP-8-1 Q1