Analog-Devices-AD8319ACPZ-R7
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1 MHz to 10 GHz, 40 dB
Log Detector/Controller
AD8319
FUNCTIONAL BLOCK DIAGRAM
FEATURES
Wide bandwidth: 1 MHz to 10 GHz
VPOS
TADJ
High accuracy:
1.0 dB over temperature
>40 dB dynamic range up to 8 GHz
Stability over temperature
0.5 dB
Low noise measurement/controller output VOUT
Pulse response time: 8/10 ns (fall/rise)
Small footprint 2 mm x 3 mm CSP package
Supply operation: 3.0V to 5.5V @ 22 mA
Fabricated using high speed SiGe process
GAIN
BIAS
SLOPE
VSET
I
I
V
V
VOUT
CLPF
DET
DET
DET
DET
INHI
INLO
COMM
APPLICATIONS
Figure 1.
RF transmitter PA setpoint control and level monitoring
Power monitoring in radiolink transmitters
RSSI measurement in base stations, WLAN, WiMAX, radar
GENERAL DESCRIPTION
The feedback loop through an RF amplifier is closed via VOUT,
the output of which regulates the amplifier
’
s
o
utput to a
magnitude corresponding to V
SET
. The AD8319 provides
0 V to (
V
POS
− 0.1 V) output capability at the VOUT pin,
suitable for controller applications. As a measurement device,
VOUT is externally connected to VSET to produce an output
voltage V
OUT
that is a decreasing linear-in-dB function of the RF
input signal amplitude.
The AD8319 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 AD8319 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 40 dB (re: 50
Ω
) with error less than
±
1 dB. The
AD8319 has 8/10 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 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 AD8319 is fabricated on a SiGe bipolar IC process and is
available in a 2 mm × 3 mm, 8-lead LFCSP_VD package for an
operating temperature range of –40
o
C to +85
o
C.
The AD8319 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.
Rev. 0
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 registere
d
t
rademarks ar
e
t
he property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
Fax: 781.461.3113
©2005 Analog Devices, Inc. All rights reserved.
AD8319
TABLE OF CONTENTS
Basic Connection
s
.
…………………………………………………………… 11
REVISION HISTORY
10/05—Revision 0: Initial
V
e
rsion
Rev. 0 | Page 2 of 20
AD8319
SPECIFICATIONS
V
POS
= 3
V
,
C
LPF
= 1000 p
F
,
T
A
= 25
°
C, 52.3 Ω termination resistor at INHI, unless otherwise noted.
Table 1.
Parameter
Conditions
Min
Typ
Max
10
Unit
SIGNAL INPUT INTERFACE
Specified Frequency Range
DC Common-Mode Voltage
MEASUREMENT MODE
INHI (Pin 1)
0.001
GHz
V
V
POS
– 0.6
VOUT (Pin 5) shorted to VSET (Pin 4), sinusoidal input
signal
f = 900 MHz
R
TADJ
= 18 k
Ω
Input Impedance
±
1 dB Dynamic Range
1500||0.33
40
Ω||pF
dB
T
A
= +25
°
C
40
dB
−
40
°
C < T
A
< +85
°
C
±
1 dB error
±
1 dB error
Maximum Input Level
Minimum Input Level
−3
dBm
dBm
−43
−22
15
0.57
1.25
−25
12
−19.5 mV/dB
21
dBm
V
V
Output Voltage: High Power In
Output Voltage: Low Power In
f = 1.9 GHz
P
IN
= –10 dBm
P
IN
= –40 dBm
R
TADJ
= 8 k
Ω
Input Impedance
950||0.38
40
Ω||pF
dB
±
1 dB Dynamic Range
T
A
= +25
°
C
40
dB
−40
°
C < T
A
< +85
°
C
±
1 dB error
Maximum Input Level
Minimum Input Level
−4
dBm
dBm
−44
−22
13
0.53
1.19
±
1 dB error
−25
10
−19.5 mV/dB
20
dBm
V
V
Output Voltage: High Power In
Output Voltage: Low Power In
f = 2.2 GHz
P
IN
= –10 dBm
P
IN
= –35 dBm
R
TADJ
= 8 k
Ω
Input Impedance
810||0.39
40
Ω
||pF
dB
±
1 dB Dynamic Range
T
A
= +25
°
C
40
dB
−40
°
C < T
A
< +85
°
C
±
1 dB error
Maximum Input Level
Minimum Input Level
−5
dBm
dBm
mV/dB
dBm
V
−45
−22
13
0.5
1.18
±
1 dB error
Output Voltage: High Power In
Output Voltage: Low Power In
f = 3.6 GHz
P
IN
= –10 dBm
P
IN
= –35 dBm
R
TADJ
= 8 k
Ω
V
Input Impedance
300||0.33
40
Ω
||pF
dB
±
1 dB Dynamic Range
T
A
= +25
°
C
36
dB
−40
°
C < T
A
< +85
°
C
±
1 dB error
Maximum Input Level
Minimum Input Level
Output Voltage: High Power In
Output Voltage: Low Power In
−6
dBm
dBm
mV/dB
dBm
V
−46
−22
10
0.46
1.14
±
1 dB error
P
IN
= –10 dBm
P
IN
= –40 dBm
V
Rev. 0 | Page 3 of 20
AD8319
Parameter
Conditions
Min
Typ
Max
Unit
f = 5.8 GHz
R
TADJ
= 500
Ω
Input Impedance
110||0.05
40
Ω||pF
dB
±
1 dB Dynamic Range
T
A
= +25
°
C
40
dB
−
40
°
C < TA < +85
°
C
±
1 dB error
Maximum Input Level
Minimum Input Level
−3
dBm
dBm
mV/dB
dBm
V
−43
−22
15
0.57
1.25
±
1 dB error
Output Voltage: High Power In
Output Voltage: Low Power In
f = 8.0 GHz
P
IN
= –10 dBm
P
IN
= –40 dBm
R
TADJ
= open
V
Input Impedance
28||0.79
40
ꢀ||
pF
dB
±
1 dB Dynamic Range
T
A
= +25
°
C
31
dB
−
40
°
C < T
A
< +85
°
C
±
1 dB error
±
1 dB error
Maximum Input Level
Minimum Input Level
−1
dBm
dBm
mV/dB
dBm
V
−41
−22
20
0.67
1.34
Output Voltage: High Power In
Output Voltage: Low Power In
OUTPUT INTERFACE
Voltage Swing
P
IN
= –10 dBm
P
IN
= –40 dBm
V
VOUT (Pin 5)
V
SET
= 0 V; RFIN = open
V
POS
– 0.1
V
V
SET
= 1.5 V; RFIN = open
10
10
140
90
18
6
mV
mA
MHz
Output Current Drive
Small Signal Bandwidth
Output Noise
V
SET
= 0 V; RFIN = open
RFIN = −10 dBm; from CLPF to VOUT
RF Input = 2.2 GHz, –10 dBm, f
NOISE
= 100 kHz, C
LPF
= open
Input level = no signal to −10 dBm, 90% to 10%; C
LPF
= 8 pF
nV/
√
Hz
ns
Fall Time
Fall Time
Input level = no signal to −10 dBm, 90% to 10%;
C
LPF
= open; R
OUT
= 150 Ω
ns
Rise Time
Rise Time
Input level = –10 dBm to no signal, 10% to 90%; C
LPF
= 8 pF
20
10
ns
ns
Input level = –10 dBm to no signal, 10% to 90%;
C
LPF
= open; R
OUT
= 150 Ω
Video Bandwidth (or Envelope
Bandwidth)
50
MHz
VSET INTERFACE
VSET (Pin 4)
Nominal Input Range
RFIN = 0 dBm; measurement mode
RFIN = –40 dBm; measurement mode
0.35
1.23
−45
40
V
Logarithmic Scale Factor
Input Resistance
dB/V
k
Ω
RFIN = −20 dBm; controller mode; V
SET
= 1 V
TADJ (Pin 6)
TADJ INTERFACE
Input Resistance
TADJ = 0.9 V, sourcing 50 μA
TADJ = Open
40
k
Ω
Disable Threshold Voltage
POWER INTERFACE
Supply Voltage
V
POS
– 0.4
VPOS (Pin 7)
3.0
18
5.5
30
V
Quiescent Current
vs. Temperature
22
mA
μA/°C
μA
60
−40
°
C
≤
T
A
≤
+85
°
C
TADJ = VPOS
Disable Current
200
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.
Rev. 0 | Page 4 of 20
AD8319
ABSOLUTE MAXIMUM RATINGS
Table 2.
Parameter
Supply Voltage: V
POS
V
SET
Voltage
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.
Rating
5.7 V
0 to V
POS
12 dBm
0.73
Input Power (Single-Ended, Re: 50
Ω
)
Internal Power Dissipation
θ
JA
Maximum Junction Temperature
Operating Temperature Range
Storage Temperature Range
Lead Temperature (Soldering 60 sec)
55
°
C/W
125°C
−40°C to +85°C
−65°C to +150°C
260°C
ESD 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 this product 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. 0 | Page 5 of 20
AD8319
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
INHI
COMM
CLPF
1
2
3
4
8
7
6
5
INLO
VPOS
TADJ
VOUT
AD8319
TOP VIEW
(Not to Scale)
VSET
Figure 2. Pin Configuration
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
3
COMM
CLPF
Device Common. Connect to a low impedance ground plane.
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
5
VSET
VOUT
Setpoint Control Input for Controller Mode or Feedback Input for Measurement Mode.
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
8
VPOS
INLO
Positive Supply Voltage: 3.0 V to 5.5 V.
RF Common for INHI. AC-coupled RF common.
Paddle
Internally connected to COMM; solder to a low impedance ground plane.
Rev. 0 | Page 6 of 20
AD8319
TYPICAL PERFORMANCE CHARACTERISTICS
V
POS
= 3 V; T = 25
°
C,
–
40
°
C, +85
°
C; C
LPF
= 1000 pF; unless otherwise noted. Colors: 25
°
C
ꢀ
Black; -40
°
C
ꢀ
Blue; 85
°
C
ꢀ
Red
Error is calculated by using the best-fit line between P
IN
= −40 dBm and P
IN
= −10 dBm at the specified input frequency, unless otherwise noted.
2.0
2.0
2.00
2.00
1.75
1.5
1.75
1.5
1.0
1.0
1.50
1.25
1.00
0.75
0.50
0.25
0
1.50
1.25
1.00
0.75
0.50
0.25
0
0.5
0.5
0
0
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
–60
–50
–40
–30
–20
(dBm)
–10
0
10
–60
–50
–40
–30
–20
(dBm)
–10
0
10
P
P
IN
IN
Figure 3. V
OUT
and Log Conformance vs. Input Amplitude at 900 MHz,
R
TADJ
= 18 kΩ
Figure 6. V
OUT
and Log Conformance vs. Input Amplitude at 3.6 GHz,
R
TADJ
= 8 kΩ
2.0
2.0
2.00
1.75
2.00
1.75
1.5
1.5
1.0
1.0
1.50
1.25
1.00
0.75
0.50
0.25
0
1.50
1.25
1.00
0.75
0.50
0.25
0
0.5
0.5
0
0
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
–60
–50
–40
–30
–20
(dBm)
–10
0
10
–60
–50
–40
–30
–20
(dBm)
–10
0
10
P
P
IN
IN
Figure 4. V
OUT
and Log Conformance vs. Input Amplitude at 1.9 GHz,
R
TADJ
= 8 kΩ
Figure 7. V
OUT
and Log Conformance vs. Input Amplitude at 5.8 GHz,
R
TADJ
= 500 Ω
2.0
2.0
2.00
1.75
2.00
1.75
1.5
1.5
1.0
1.0
1.50
1.25
1.00
0.75
0.50
0.25
0
1.50
1.25
1.00
0.75
0.50
0.25
0
0.5
0.5
0
0
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
–60
–50
–40
–30
–20
(dBm)
–10
0
10
–60
–50
–40
–30
–20
(dBm)
–10
0
10
P
P
IN
IN
Figure 5. V
OUT
and Log Conformance vs. Input Amplitude at 2.2 GHz,
R
TADJ
= 8 kΩ
Figure 8. V
OUT
and Log Conformance vs. Input Amplitude at 8.0 GHz,
R
TADJ
= Open, Error Calculated from P
IN
= −34 dBm to P
IN
= -16 dBm
Rev. 0 | Page 7 of 20
AD8319
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
2.0
1.5
2.00
1.75
1.0
1.50
1.25
1.00
0.75
0.50
0.25
0
0.5
0
–0.5
–1.0
–1.5
–2.0
0
–60
–50
–40
–30
P
–20
(dBm)
–10
0
10
–60
–50
–40
–30
P
–20
(dBm)
–10
0
10
IN
IN
Figure 9. V
OUT
and Log Conformance vs. Input Amplitude at 900 MHz,
Multiple Devices, R
TADJ
= 18 kΩ
Figure 12. V
OUT
and Log Conformance vs. Input Amplitude at 3.6 GHz,
Multiple Devices, R
TADJ
= 8 kΩ
2.0
1.5
2.00
1.75
2.0
1.5
2.00
1.75
1.0
1.50
1.25
1.00
0.75
0.50
0.25
0
1.0
1.50
1.25
1.00
0.75
0.50
0.25
0
0.5
0.5
0
0
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
–60
–50
–40
–30
P
–20
(dBm)
–10
0
10
–60
–50
–40
–30
P
–20
(dBm)
–10
0
10
IN
IN
Figure 10. V
OUT
and Log Conformance vs. Input Amplitude at 1.9 GHz,
Multiple Devices, R
TADJ
= 8 kΩ
Figure 13. V
OUT
and Log Conformance vs. Input Amplitude at 5.8 GHz,
Multiple Devices, R
TADJ
= 500 Ω
2.0
1.5
2.00
1.75
2.0
1.5
2.00
1.75
1.0
1.50
1.25
1.00
0.75
0.50
0.25
0
1.0
1.50
1.25
1.00
0.75
0.50
0.25
0
0.5
0.5
0
0
–0.5
–1.0
–1.5
–2.0
–0.5
–1.0
–1.5
–2.0
–60
–50
–40
–30
P
–20
(dBm)
–10
0
10
–60
–50
–40
–30
P
–20
(dBm)
–10
0
10
IN
IN
Figure 11. V
OUT
and Log Conformance vs. Input Amplitude at 2.2 GHz,
Multiple Devices, R
TADJ
= 8 kΩ
Figure 14. V
OUT
and Log Conformance vs. Input Amplitude at 8.0 GHz,
Multiple Devices, R
TADJ
=Open,
Error Calculated from P
IN
= −34 dBm to P
IN
= −16 dBm
Rev. 0 | Page 8 of 20
AD8319
j1
j2
j0.5
10000
1000
100
j0.2
–60dBm
0
0.2
0.5
1
2
RF OFF
–20dBm
100MHz
900MHz
–10dBm
–j0.2
–40dBm
0dBm
1900MHz
2200MHz
8000MHz
–j0.5
–j2
3600MHz
10
1k
–j1
START FREQUENCY = 0.05GHz
STOP FREQUENCY = 10GHz
10M
10k
100k
FREQUENCY (Hz)
1M
5800MHz
10000MHz
Figure 18. Noise Spectral Density of Output; C
LPF
= Open
Figure 15. Input Impedance vs. Frequency; No Termination Resistor on INHI
(Impedance De-Embedded to Input Pins), Z
0
= 50 Ω
10000
Δ
: 1.53V
@ : 1.53V
1000
100
10
1
M2.00
μ
s
A CH1
420V
Ch1
500mV
10M
1k
10k
100k
1M
T
29.60%
FREQUENCY (Hz)
Figure 16. Power On/Off Response Time; V
P
= 3.0 V;
Input AC-Coupling Caps = 10 pF; C
LPF
= Open
Figure 19. Noise Spectral Density of Output Buffer (from CLPF to VOUT);
C
LPF
= 0.1 μF
2.0
2.00
1.75
CH1 RISE
9.949ns
3.3V
3.0V
1.5
CH1 FALL
6.032ns
3.6V
1.0
1.50
1.25
1.00
0.75
0.50
0.25
0.5
0
–0.5
–1.0
–1.5
–2.0
0
1
–60 –55 –50 –45 –40 –35 –30 –25 –20 –15 –10
–5
0
5
10
Ch1
200mV
M20.0ns
T
72.40%
A CH1
1.04V
P
(dBm)
IN
Figure 17. V
OUT
Pulse Response Time; Pulsed RF Input 0.1 GHz, −10 dBm;
C
LPF
= Open; R
LOAD
= 150 Ω
Figure 20. Output Voltage Stability vs. Supply Voltage at 1.9 GHz
When V
POS
Varies by 10%
Rev. 0 | Page 9 of 20
AD8319
THEORY OF OPERATION
The AD8319 is a 5-stage demodulating logarithmic amplifier,
specifically designed for use in RF measurement and power
logarithmic detector/controller, the AD8319 maintains tight
intercept variability vs. temperature over a 40 dB range. Additional
space requirements of only 2 mm x 3 mm add to the low cost
and high performance benefits found in the AD8319.
The logarithmic function is approximated in a piecewise
fashion by five cascaded gain stages. (For a more comprehensive
explanati
on of the logarithm approximation, please refer to the
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.
VPSO
TADJ
The RF signal voltages are converted to a fluctuating differential
current having an average value that increases with signal level.
Along with the five gain stages and detector cells, an additional
detector is included at the input of the AD8319, providing a
40 dB dynamic range in total. After the detector currents are
summed and filtered, the following function is formed at the
summing node:
GAIN
BIAS
SLOPE
VSET
I
V
VOUT
CLPF
I
V
DET
DET
DET
DET
INHI
INLO
I
D
× log
10
(
V
IN
/
V
INTERCEPT
where:
I
D
is the internally set detector current.
)
COMM
Figure 21. Block Diagram
A fully differential design, using a proprietary, high speed
V
IN
is the input signal voltage.
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 p
F
.
T
he maximum input
with 1
dB log-conformance 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 ꢁV 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 AD8319 is enhanced by
specially shaping the demodulating transfer characteristic to
partially 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.
V
INTERCEPT
is the intercept voltage (that is, when
V
IN
=
V
INTERCEPT
,
the output voltage would be 0
V
,
i
f it were capable of going to 0 V).
Rev. 0 | Page 10 of 20
AD8319
USING THE AD8319
combines with the relatively high input impedance to give an
adequate broadband 50
Ω
match.
BASIC CONNECTIONS
The AD8319 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 ꢁF should be connected close to
this power supply pin.
The coupling time constant, 50 × C
C
/2, forms a high-pass
corner with a 3 dB attenuation at f
HP
= 1/(2π × 50 × C
C
), where
C1 = C2 = C
C
. Using the typical value of 47 n
F
,
t
his high-pass
corner will be ~68 kHz. In high frequency applications, f
HP
should be 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 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.
V (2.7V–5.5V)
S
C5
0.1
μ
F
R2
0
Ω
C4
100pF
SEE TEXT
C2
V
OUT
47nF
OUTPUT INTERFACE
8
7
6
5
INLO VPOS
TADJ
VOUT
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 VOU
T
.
T
here 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.
R4
0
Ω
R1
52.3
Ω
AD8319
INHI
1
COMM CLPF
2
VSET
4
3
C1
SIGNAL
INPUT
SEE TEXT
47nF
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.
VPOS
CLPF
10
Ω
VOUT
INPUT SIGNAL COUPLING
+
0.8V
–
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 input stage’s high-pass cutoff frequency. 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
1200
Ω
400
Ω
COMM
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 AD8319 fall time is <7 ns.
SETPOINT INTERFACE
INLO is about one diode voltage drop below V
POS
.
The V
SET
input drives the high impedance (20 k
Ω
) input of an
internal op amp. The V
SET
voltage appears across the internal
1.5 k
Ω
resistor to generate I
SET
. When a portion of V
OUT
is
applied to VSET, the feedback loop forces
VPOS
5pF
CURRENT
5pF
FIRST
GAIN
STAGE
18.7k
Ω
INHI
18.7k
Ω
−I
D
× log
10
(
V
IN
/
V
INTERCEPT
) =
I
SET
.
2k
Ω
A = 9dB
If
V
SET
=
V
OUT
/2x, then
I
SET
=
V
OUT
/(2x × 1.5 k
Ω
).
INLO
The result is
Gm
STAGE
OFFSET
COMP
V
OUT
= (−
I
D
× 1.5 kꢀ × 2x) × log
10
(V
IN
/V
INTERCEPT
)
Figure 23. Input Interface
While the input can be reactively matched, in general this is not
necessary. An external 52.3
Ω
shunt resistor (connected on the
Rev. 0 | Page 11 of 20
AD8319
I
SET
MEASUREMENT MODE
20k
Ω
V
SET
VSET
When the V
OUT
voltage or a portion of the V
OUT
voltage is fed
back to the VSET pin, the device operates in measurement
a negative slope, and a V
OUT
measurement intercept at the high
end of its input signal range.
20k
Ω
1.5k
Ω
COMM
COMM
Figure 25. VSET Interface
2.00
1.75
1.50
1.25
1.00
0.75
0.50
0.25
0
2.0
1.5
1.0
0.5
0
V
25°C
OUT
ERROR 25°C
The slope is given by −
I
D
× 2x × 1.5 k
Ω
= −22 mV/dB × x. For
example, if a resistor divider to ground is used to generate a V
SET
voltage of V
OUT
/2, then x = 2. The slope is set to −880 V/decade
or −44 mV/dB.
TEMPERATURE COMPENSATION OF OUTPUT
VOLTAGE
–0.5
–1.0
The primary component of the variation in V
OUT
vs. temperature,
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, so provision is made for optimization of internal
temperature compensation at a given frequency by providing
Pin TADJ.
RANGE FOR
CALCULATION OF
SLOPE AND INTERCEPT
–1.5
–60 –55 –50 –45 –40 –35 –30 –25 –20 –15 –10
–5
0
5
10 15
INTERCEPT
P
(dBm)
IN
Figure 27. Typical Output Voltage vs. Input Signal
AD8319
V
INTERNAL
I
COMP
The output voltage vs. input signal voltage of the AD8319 is
linear-in-dB over a multidecade range. The equation for this
function is of the form
TADJ
R
TADJ
V
OUT
=
X
×
V
SLOPE/DEC
× log
10
(
V
IN
/
V
INTERCEPT
) =
X
×
V
SLOPE/dB
× 20 × log
10
(
V
IN
/V
INTERCEPT
where:
X
is the feedback factor in
V
SET
=
V
OUT
/X.
(1)
(2)
1.5k
Ω
)
COMM
COMM
Figure 26. TADJ Interface
The Resistor R
TADJ
is connected between this pin and ground.
The value of this resistor partially determines the magnitude
of an analog correction coefficient, which is used to reduce
intercept drift.
V
V
SLOPE/DEC
is nominally −440 mV/decade or −22 mV/dB.
INTERCEPT
is the x-axis intercept of the linear-in-dB portion of
INTERCEPT
is +2 dBV for a sinusoidal input signal.
V
The relationship between output temperature drift and fre-
quency is not linear and cannot be easily modeled. As a result,
experimentation is required to choose the correct TADJ resistor.
used frequencies.
An offset voltage, V
OFFSET
, of 0.35 V is internally added to the
detector signal, so that the minimum value for V
OUT
is
X × V
OFFSET
, so for X = 1, minimum V
OUT
is 0.35
V
.
The slope is very stable vs. process and temperature variation.
When base-10 logarithms are used, V
SLOPE/DECADE
represents the
volts/decade. A decade corresponds to 20 dB; V
SLOPE/DECADE
/20 =
Table 4. Recommended R
TADJ
Resistor Values
Frequency
50 MHz
100 MHz
900 MHz
1.8 GHz
1.9 GHz
2.2 GHz
3.6 GHz
5.3 GHZ
5.8 GHz
8 GHz
Recommended R
TADJ
V
SLOPE/dB
represents the slope in volts/dB.
18 kΩ
18 kΩ
18 kΩ
8 kΩ
8 kΩ
8 kΩ
As noted in the Equation 1 and Equation 2, the V
OUT
voltage has
a
negative
slope. This is also the correct slope polarity to control
the gain of many power amplifiers in a negative feedback configu-
ration. Because both the slope and intercept vary slightly with
section for application-specific values for slope and intercept.
8 kΩ
500 Ω
500 Ω
Open
Rev. 0 | Page 12 of 20
AD8319
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
0
, must be
known to convert voltages to their corresponding power levels.
The following equations are used to perform this conversion.
CONTROLLER MODE
The AD8319 provides a controller mode feature at the VOUT
pin. Using V
SET
for the setpoint voltage, it is possible for the
AD8319 to control subsystems, such as power amplifiers (PAs),
variable gain amplifiers (VGAs), or variable voltage attenuators
(V
V
A
s) that have output power that increases monotonically
with respect to their gain control signal.
P
(dBm) = 10 × log
10
(
V
rms
2
/(
Z
0
× 1 mW))
P
(dBV) = 20 × log
10
(
V
rms
/1
V
rms
P
(dBm) =
P
(dBV) − 10 × log
10
(
Z
0
× 1 mW/1
V
rms
(3)
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
variable gain amplifier (VGA) and the detector
’
s
R
F input is
connected to the output of the VGA (usually using a directional
coupler and some additional attenuation). Based on the defined
relationship between V
OUT
and the RF input signal when the
device is in measurement mode, the AD8319 adjusts the voltage
on VOUT (VOUT is now an error amplifier output) until the
level at the RF input corresponds to the applied V
SET
. When the
AD8319 operates in controller mode, there is no defined relation-
ship between V
SET
and V
OUT
voltage; V
OUT
settles to a value that
results in the correct input signal level appearing at INHI/INLO.
)
(4)
(5)
2
)
For example, P
INTERCEPT
for a sinusoidal input signal expressed in
terms of dBm (decibels referred to 1 mW), in a 50 Ω system is
P
INTERCEPT
(dBm) =
P
INTERCEPT
(dBV) − 10 × log
10
(
Z
0
×
1 mW/1
V
rms
2
) =
(6)
+2 dBV − 10 × log
10
(50×10
-3
) = +15 dBm
For a square wave input signal in a 200 Ω system
P
INTERCEPT
= −1 dBV − 10 × log
10
[(200 Ω × 1 mW/1
V
rms
2
)]
= +6 dBm
For this output power control loop to be stable, a ground-
referenced capacitor must be connected to the CLPF pin. This
capacitor, C
FLT
, integrates the error signal (in the form of a
current) to set the loop bandwidth and ensure loop stability.
Further details on control loop dynamics can be found in the
Further information on the intercept variation dependence upon
SETTING THE OUTPUT SLOPE
IN MEASUREMENT MODE
To operate in measurement mode, VOUT must be connected
to VSE
T
.
C
onnecting VOUT directly to VSET yields the nominal
logarithmic slope of −22 mV/dB. The output swing corresponding
to the specified input range is then 0.35 V to 1.5
V
.
T
he 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 imped-
ance of VSET is 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
−
44 mV/dB.
VGA/VVA
GAIN
RFIN
DIRECTIONAL
COUPLER
CONTROL
VOLTAGE
ATTENUATOR
47nF
47nF
VOUT
INHI
AD8319
52.3
Ω
DAC
VSET
INLO
CLPF
C
FLT
AD8319
VOUT
–44mV/dB
Figure 29. AD8319 Controller Mode
10k
Ω
10k
Ω
VSET
Decreasing V
SET
, which corresponds to demanding a higher
signal from the VGA, increases V
OUT
. The gain control voltage
of the VGA must have a positive sense. A positive control
voltage to the VGA increases the gain of the device.
Figure 28. Increasing the Slope
Rev. 0 | Page 13 of 20
AD8319
4
30
20
The basic connections for operating the AD8319 in an automatic
gain control (AGC) loop with the ADL5330 are shown in
Figure 30
. The ADL5330 is a 10 MHz to 3 GHz variable gain
amplifier. It offers a large gain control range of 60 dB with
3
2
10
0
1
AD8319. This voltage, V
OUT
, has a range of 0 V to near VPOS.
To avoid overdrive recovery issues, the AD8319 output voltage
0
–10
–20
–30
–40
–50
–1
–2
–3
–4
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 AD8319 (approximately −5 dBm
at 900 MHz).
0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6
SETPOINT VOLTAGE (V)
P
IN
= −1.5 dBm
+5V
+5V
RF INPUT
SIGNAL
RF OUTPUT
SIGNAL
For the AGC loop to remain in equilibrium, the AD8319 must
Figure 32
shows an oscilloscope screenshot of the AGC loop
the VGA is a constant envelope sine wave with amplitude
corresponding to a setpoint voltage at the AD8319 of 1.3
V
.
Also shown is the gain control response of the AD8319 to the
changing input envelope.
120nH
100pF
120nH
VPOS
COMM
OPHI
100pF
100pF
INHI
ADL5330
100pF
DIRECTIONAL
COUPLER
INLO
OPLO
GAIN
4.12k
Ω
+5V
ATTENUATOR
10k
Ω
VOUT
SETPOINT
VOLTAGE
VPOS
47nF
VSET
INHI
DAC
AD8319
52.3
Ω
LOG AMP
CLPF
INLO
1nF
47nF
TADJ
COMM
18k
Ω
AM MODULATED INPUT
1
Figure 31
shows the transfer function of the output power vs.
the V
SET
voltage over temperature for a 900 MHz sine wave with
an input power of −1.5 dBm. Note that the power control of the
AD8319 has a negative sense. Decreasing V
SET
, which corresponds
AD8319 OUTPUT
3
The AGC loop is capable of controlling signals of ~40 dB. This
range limitation is due to the dynamic range of the AD8319.
most accura
te over the highest power range, where it is gener-
ally most critical. Across the top 40 dB range of output power,
the linear conformance error is well within
0.5 dB over
temperature.
ADL5330 OUTPUT
2
CH1 200mV
Ch2
200mV
M2.00ms
0.00000 s
A Ch2
1.03V
T
Ch3
100mV
Ω
Figure 32. Oscilloscope Screenshot Showing an AM Modulated Input Signal
and the Response from the AD8319
Figure 33
shows the response of the AGC RF output to a pulse
on VSE
T
. As V
SET
decreases from 1.5 V to 0.4
V
,
t
he AGC loop
Rev. 0 | Page 14 of 20
AD8319
T
C
FLT
is selected using the following equation:
AD8319 VSET PULSE
1
(10)
C
FLT
=
−
3.5 pF
(
π
×
1.5 k
Ω ×
Video Bandwidth
)
1
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.
ADL5330 OUTPUT
3
In many log amp applications, it may be necessary to lower the
corner frequency of the postdemodulation filtering to achieve
low output ripple while maintaining a rapid response time to
Ch1 2.00V
Ch3
50mV
Ω
M10.0
μ
s
179.800
μ
s
A Ch1
2.60V
T
Figure 33. Oscilloscope Screenshot Showing the
Response Time of the AGC Loop
OPERATION BEYOND 8 GHZ
Response time and the amount of signal integration are
controlled by C
FLT
. This functionality is analogous to the
feedback capacitor around an integrating amplifier. While it is
possible to use large capacitors for C
FLT
, in most applications
values under 1 nF provide sufficient filtering.
The AD8319 is specified for operation up to 8 GHz, but it provides
useful measurement accuracy over a reduced dynamic range of
over temperature at 10 GHz when the device is configured as
but the AD8319 does provide 30 dB of measurement range within
3 dB of linearity error.
Calibration in controller mode is similar to the method used in
measurement mode. A simple two-point calibration can be
done by applying two known V
SET
voltages or DAC codes and
measuring the output power from the VGA. Slope and intercept
can then be calculated with the following equations:
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
5
4
3
2
Slope
= (
V
SET1
−
V
SET2
)/(
P
OUT1
−
P
OUT2
Intercept
=
P
OUT1
−
V
SET1
/
Slope
)
(7)
(8)
(9)
1
0
–1
–2
–3
–4
–5
V
SETX
=
Slope
× (
P
OUTX
−
Intercept
)
OUTPUT FILTERING
–40
–35
–30
–25
–20
–15
–10
–5
0
5
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.
P
(dBm)
IN
Figure 35. V
OUT
and Log Conformance vs. Input Amplitude at 10.0 GHz,
Multiple Devices, R
TADJ
= Open, C
LPF
= 1000 pF
The nominal output video bandwidth of 50 MHz can be
reduced by connecting a ground-referenced capacitor (C
FLT
) to
reduce output ripple (at twice the input frequency for a
symmetric input waveform such as sinusoidal signals).
Implementing an impedance match for frequencies beyond 8 GHz
can improve the sensitivity of the AD8319 and measurement
range.
Operation beyond 10 GHz is possible, but part to part variation,
most notably in the intercept, becomes significant.
AD8319
I
LOG
VOUT
CLPF
+4
1.5k
Ω
3.5pF
C
FLT
Figure 34. Lowering the Postdemodulation Bandwidth
Rev. 0 | Page 15 of 20
AD8319
EVALUATION BOARD
Table 5. Evaluation Board (Rev. A) Configuration Options
Default
Conditions
Component
VPOS, GND
R1, C1, C2
Function
Supply and Ground Connections.
Input Interface.
Not applicable
R1 = 52.3
Ω
(Size 0402)
C1 = 47 nF
(Size 0402)
C2 = 47 nF
(Size 0402)
The 52.3
Ω
resistor in position R1 combines with the AD8319’s internal input impedance to give a
broadband input impedance of about 50
Ω
. Capacitor C1 and Capacitor 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.
R5, R7
Temperature Compensation Interface.
R5 = 200
Ω
(Size 0402)
The internal temperature compensation network is optimized for input signals up to 3.6 GHz when R7 is 10
k
Ω
. This circuit can be adjusted to optimize performance for other input frequencies by changing the
R7 = open
(Size 0402)
R2, R3, R4, R6,
Output Interface—Measurement Mode.
RL, CL
R2 = 0
Ω
(Size
0402)
In measurement mode, a portion of the output voltage is fed back to Pin VSET via R2. The magnitude of the
slope of the VOUT output voltage response
can be increased by reducing the portion of V
OUT
that is fed back to VSET.
R6 can be used as a back-terminating resistor or as part of a single-pole low-pass filter.
R3 = open
(Size 0402)
R4 = open
(Size 0402)
R6 = 1 k
Ω
(Size
0402)
RL = CL =
open (Size
0402)
R2, R3
Output Interface—Controller Mode.
R2 = open
(Size 0402)
R3 = open
(Size 0402)
In this mode, R2 must be open. In controller mode, the AD8319 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 AD8319 RF input. A sample of the RF output signal from this variable-gain
component is selected, typically via a directional coupler, and applied to AD8319 RF input. The voltage
at Pin VOUT is applied to the gain control of the variable gain element. A control voltage is applied to Pin
VSET. 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.
C4, C5,
C3
Power Supply Decoupling.
The nominal supply decoupling consists of a 100 pF filter capacitor placed physically close to the
AD8319 and a 0.1 ꢀF capacitor placed nearer to the power supply input pin.
C5 = 100 pF
(Size 0402)
C4 = 0.1 ꢀF
(Size 0603)
Filter Capacitor.
C3 = 8.2 pF
(Size 0402)
The low-pass corner frequency of the circuit that drives Pin VOUT can be lowered by placing a capacitor
between CLPF and ground. Increasing this capacitor increases the overall rise/fall time of the AD8319 for
Rev. 0 | Page 16 of 20
AD8319
VPOS
C4
TADJ
GND
R5
200
Ω
0.1
μ
F
VOUT_ALT
C5
R4
R7
OPEN
OPEN
100pF
C1
R6
V
OUT
1k
Ω
47nF
CL
RL
8
7
6
5
OPEN OPEN
INLO VPOS
TADJ
VOUT
R2
R1
52.3
Ω
AD8319
0
Ω
INHI
1
COMM CLPF
VSET
4
2
3
RFIN
C2
C3
8.2pF
V
SET
47nF
R3
OPEN
Figure 36. Evaluation Board Schematic (Rev. A)
Figure 37. Component Side Layout
Figure 38. Component Side Silkscreen
Rev. 0 | Page 17 of 20
AD8319
OUTLINE DIMENSIONS
1.89
1.74
1.59
3.25
3.00
2.75
0.55
0.40
0.30
0.60
0.45
0.30
5
4
8
*
2.25
2.00
1.75
BOTTOM VIEW
1.95
1.75
1.55
TOP VIEW
EXPOSED PAD
0.15
0.10
0.05
1
2.95
2.75
2.55
PIN 1
INDICATOR
0.25
0.20
0.15
0.50 BSC
12° MAX
0.80 MAX
0.65 TYP
1.00
0.85
0.80
0.05 MAX
0.02 NOM
0.30
0.23
0.18
SEATING
PLANE
0.20 REF
Figure 39: 8-Lead Lead Frame Chip Scale Package [LFCSP_VD]
2 mm x 3 mm Body, Very Thin, Dual Lead
(CP-8-1)
Dimensions shown in millimeters
Model
AD8319ACPZ-R7
1
AD8319ACPZ-R2
1
AD8319ACPZ-WP
1, 2
AD8319-EVAL
Temperature Range
Package Description
8-Lead LFCSP_VD
8-Lead LFCSP_VD
8-Lead LFCSP_VD
Evaluation Board
Package Option
CP-8-1
CP-8-1
Branding
–40°C to +85°C
–40°C to +85°C
–40°C to +85°C
Q2
Q2
Q2
Q2
CP-8-1
1
Z = Pb-free part.
2
WP = waffle pack.
Rev. 0 | Page 18 of 20
AD8319
NOTES
Rev. 0 | Page 19 of 20
AD8319
NOTES
©2005 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D05705-0-10/05(0)
Rev. 0 | Page 20 of 20
