LINER LT5581IDDB

LT5581
6GHz RMS Power Detector
with 40dB Dynamic Range
FEATURES
DESCRIPTION
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The LT®5581 is a 10MHz to 6GHz, low power monolithic
precision RMS power detector. The RMS detector uses
a proprietary technique to accurately measure the RF
power from –34dBm to +6dBm (at 2.14GHz) of modulated
signals with a crest factor as high as 12dB. It outputs a DC
voltage in linear scale proportional to an RF input signal
power in dBm. The LT5581 is suitable for precision power
measurement and control for a wide variety of RF standards,
including GSM/EDGE, CDMA, CDMA2000, W-CDMA, TDSCDMA, UMTS, LTE and WiMAX, etc. The final DC output
is connected in series with an on-chip 300Ω resistor, which
enables further filtering of the output modulation ripple
with just a single off-chip capacitor.
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Frequency Range: 10MHz to 6GHz
Accurate Power Measurement of High Crest Factor
(Up to 12dB) Waveforms
40dB Log Linear Dynamic Range
Exceptional Accuracy Over Temperature
Fast Response Time: 1μs Rise, 8μs Fall
Low Power: 1.4mA at 3.3V
Log-Linear DC Output vs Input RF Power in dBm
Small 3mm × 2mm 8-Pin DFN Package
Single-Ended RF Input
APPLICATIONS
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GSM/EDGE, CMDA, CDMA2000, W-CDMA, LTE,
WiMAX RF Power Control
Pico-Cells, Femto-Cells RF Power Control
Wireless Repeaters
CATV/DVB Transmitters
MIMO Wireless Access Points
Portable RMS Power Measurement Instrumentation
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents,
including 7342431.
TYPICAL APPLICATION
10MHz to 6GHz Infrastructure Power
Amplifier Level Control
DIRECTIONAL
COUPLER
POWER
AMP
3
RFOUT
TA = 25°C
2
CMATCH
VCC
2.7VDC TO 5.25VDC
0.1μF
DIGITAL
POWER
CONTROL
1
2
ADC
3
4
CFILT
0.01μF
VCC
EN
LT5581
GND
VOUT
GND
0.01μF
8
CSQ
1000pF
7
RFIN
GND
GND
50Ω
LMATCH
6
5
68Ω
9
5581 TA01a
LINEARITY ERROR (dB)
RFIN
Linearity Error vs RF Input Power,
2140MHz Modulated Waveforms
1
0
–1
–2
CW
WCDMA, UL
WCDMA DL 1C
WCDMA DL 4C
LTE DL 1C
LTE DL 4C
–3
–35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
10
5581 TA01b
5581f
1
LT5581
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
Supply Voltage .........................................................5.5V
Maximum Input Signal Power—Average .............15dBm
Maximum Input Signal Power—Peak (Note 7) ....25dBm
DC Voltage at RFIN ....................................... –0.3V to 2V
VOUT Voltage ....................................–0.3V to VCC + 0.3V
Maximum Junction Temperature, TJMAX ............... 150°C
Operating Temperature Range.................. –40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
TOP VIEW
VCC 1
8
CSQ
EN 2
7
RFIN
6
GND
5
GND
VOUT 3
9
GND 4
DDB PACKAGE
8-LEAD (3mm s 2mm) PLASTIC DFN
TJMAX = 150°C, θJA = 76°C/W
EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB
CAUTION: This part is sensitive to electrostatic discharge. It
is very important that proper ESD precautions be observed
when handling the LT5581.
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT5581IDDB#PBF
LT5581IDDB#TRPBF
LDKM
8-Lead (3mm × 2mm) Plastic DFN
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C, VCC = 3.3V, EN = 3.3V, unless otherwise noted (Note 2). Test circuit is shown in Figure 1.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
AC Input
Input Frequency Range (Note 4)
10-6000
MHz
Input Impedance
205||1.6
Ω||pF
–34 to 6
dBm
fRF = 450MHz
RF Input Power Range
Externally Matched to 50Ω Source
Linear Dynamic Range, CW (Note 3)
±1dB Linearity Error
40
dB
Linear Dynamic Range, CDMA (Note 3)
±1dB Linearity Error; CDMA 4-Carrier
40
dB
Output Slope
31
mV/dB
Logarithmic Intercept (Note 5)
–42
dBm
Output Variation vs Temperature
Normalized to Output at 25˚C, –40°C < TA < 85°C;
PIN = –34 to +6dBm
±1
dB
Output Variation vs Temperature
Normalized to Output at 25°C, –40°C < TA < 85°C;
PIN = –27 to –10dBm
±0.5
dB
Deviation from CW Response;
PIN = –34dBm to 0dBm
TETRA π/4 DQPSK
CDMA 4-Carrier 64-Channel Fwd 1.23Mcps
±0.1
±0.5
dB
dB
5581f
2
LT5581
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C, VCC = 3.3V, EN = 3.3V, unless otherwise noted (Note 2). Test circuit is shown in Figure 1.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
2nd Order Harmonic Distortion
At RF Input; CW Input; PIN = 0dBm
–57
dBc
3rd Order Harmonic Distortion
At RF Input; CW Input; PIN = 0dBm
–52
dBc
RF Input Power Range
Externally Matched to 50Ω Source
–34 to 6
dBm
Linear Dynamic Range, CW (Note 3)
±1dB Linearity Error
40
dB
Linear Dynamic Range, EDGE (Note 3)
±1dB Linearity Error; EDGE 3π/8-Shifted 8PSK
40
dB
Output Slope
31
mV/dB
Logarithmic Intercept (Note 5)
–42
dBm
fRF = 880MHz
Output Variation vs Temperature
Normalized to Output at 25°C, –40°C < TA < 85°C;
PIN = –34 to +6dBm
±1
dB
Output Variation vs Temperature
Normalized to Output at 25°C, –40°C < TA < 85°C;
PIN = –27 to –10dBm
±0.5
dB
Deviation from CW Response, Pin = –34 to +6dBm
EDGE 3π/8 Shifted 8PSK
±0.1
dB
fRF = 2140MHz
RF Input Power Range
Externally Matched to 50Ω Source
Linear Dynamic Range, CW (Note 3)
±1dB Linearity Error
Linear Dynamic Range, WCDMA (Note 3)
±1dB Linearity Error; 4-Carrier WCDMA
–34 to 6
43
dBm
dB
37
dB
Output Slope
31
mV/dB
Logarithmic Intercept (Note 5)
–42
dBm
Output Variation vs Temperature
Normalized to Output at 25°C, –40°C < TA < 85°C;
PIN = –34 to 6dBm
±1
dB
Output Variation vs Temperature
Normalized to Output at 25°C, –40°C < TA < 85°C;
PIN = –27 to –10dBm
±0.5
dB
Maximum Deviation from CW Response
PIN = –34 to –4dBm
WCDMA 1-Carrier Uplink
WCDMA 64-Channel 4-Carrier Downlink
±0.1
±0.5
dB
dB
fRF = 2600MHz
RF Input Power Range
Externally Matched to 50Ω Source
Linear Dynamic Range, CW (Note 3)
±1dB Linearity Error
Output Slope
Logarithmic Intercept (Note 5)
–34 to 6
dBm
40
dB
31
mV/dB
–42
dBm
Output Variation vs Temperature
Normalized to Output at 25°C, –40°C < TA < 85°C;
PIN = –34 to +6dBm
±1
dB
Output Variation vs Temperature
Normalized to Output at 25°C, –40°C < TA < 85°C;
PIN = –27 to –10dBm
±0.5
dB
Maximum Deviation from CW Response
PIN = –34 to 2dBm
WiMAX OFDMA Preamble
WiMAX OFDM Burst
±0.1
±0.5
dB
dB
fRF = 3500MHz
RF Input Power Range
Externally Matched to 50Ω Source
Linear Dynamic Range, CW (Note 3)
±1dB Linearity Error
–30 to 6
dBm
36
dB
Output Slope
31
mV/dB
Logarithmic Intercept (Note 5)
–41
dBm
±1
dB
Output Variation vs Temperature
Normalized to Output at 25°C, –40°C < TA < 85°C;
PIN = –30 to +6dBm
5581f
3
LT5581
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating temperature
range, otherwise specifications are at TA = 25°C, VCC = 3.3V, EN = 3.3V, unless otherwise noted (Note 2). Test circuit is shown in Figure 1.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Output Variation vs Temperature
Normalized to Output at 25°C, –40°C < TA < 85°C;
PIN = –27 to –10dBm
±0.5
dB
Deviation from CW Response
PIN = –34 to –4dBm
WiMAX OFDMA Preamble
WiMAX OFDM Burst
±0.1
±0.5
dB
dB
fRF = 5800MHz
RF Input Power Range
Externally Matched to 50Ω Source
Linear Dynamic Range, CW (Note 3)
±1dB Linearity Error
–25 to 6
dBm
31
dB
Output Slope
31
mV/dB
Logarithmic Intercept (Note 5)
–33
dBm
Output Variation vs Temperature
Normalized to Output at 25°C, –40°C < TA < 85°C;
PIN = –25 to +6dBm
±1
dB
Output Variation vs Temperature
Normalized to Output at 25°C, –40°C < TA < 85°C;
PIN = –20 to +6dBm
±0.5
dB
Deviation from CW Response
WiMAX OFDM Burst; PIN = –25 to 6dBm
±0.2
dB
Output DC Voltage
No Signal Applied to RF Input
180
mV
Output Impedance
Internal Series Resistor Allows for Off-Chip Filter Cap
300
Ω
Output
Output Current Sourcing/Sinking
5/5
mA
Rise Time
0.2V to 1.6V, 10% to 90%, fRF = 2140MHz
1
μs
Fall Time
1.6V to 0.2V, 10% to 90%, fRF = 2140MHz
8
μs
Power Supply Rejection Ratio (Note 6)
For Over Operating Input Power Range
49
dB
Integrated Output Voltage Noise
1kHz to 6.5kHz Integration BW, PIN = 0dBm CW
150
μVRMS
Enable (EN) Low = Off, High = On
EN Input High Voltage (On)
l
EN Input Low Voltage (Off)
l
2
V
0.3
V
Enable Pin Input Current
EN = 3.3V
20
μA
Turn-On Time; CW RF input
VOUT Within 10% of Final Value; PIN = 0dBm
1
μs
Settling Time; RF Pulse
VOUT Within 10% of Final Value; PIN = 0dBm
1
μs
Power Supply
l
Supply Voltage
2.7
3.3
Supply Current
No RF Input Signal
1.4
Shutdown Current
EN = 0.3V, VCC = 3.3V
0.2
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LT5581 is guaranteed to meet specified performance from
–40°C to 85°C.
Note 3: The linearity error is calculated by the difference between the
incremental slope of the output and the average output slope from
–20dBm to 0dBm. The dynamic range is defined as the range over which
the linearity error is within ± 1dB.
5.25
V
mA
6
μA
Note 4: An external capacitor at the CSQ pin should be used for input
frequencies below 250MHz. Lower frequency operation results in
excessive RF ripple in the output voltage.
Note 5: Logarithmic intercept is an extrapolated input power level from the
best fitted log-linear straight line, where the output voltage is 0V.
Note 6: PSRR is determined as the dB value of the change in VOUT voltage
over the change in VCC supply voltage.
Note 7: Not production tested. Guaranteed by design and correlation to
production tested parameters.
5581f
4
LT5581
TYPICAL PERFORMANCE CHARACTERISTICS
Performance characteristics taken at VCC = 3.3V,
EN = 3.3V and TA = 25°C, unless otherwise noted. (Test circuit shown in Figure 1)
1.2
1.0
10MHz
450MHz
880MHz
2.14GHz
2.6GHz
3.5GHz
5.8GHz
1.6
1.4
0.8
0.8
0.4
0.4
0.2
0.2
5
5581 G01
1.5
1.4
1.0
1.2
0.5
1.0
0
0.8
–0.5
0.6
–1.0
0.4
–1.5
0.2
–2.0
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
LINEARITY ERROR (dB)
VOUT (V)
1.6
3
2
2
0
85°C
–40°C
–1
5
1.0
1.2
0.5
1.0
0
0.8
–0.5
0.6
–1.0
0.4
–1.5
0.2
–2.0
–2.5
5
10
5581 G07
VARIATION (dB)
1.5
1.4
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
0
–1
–3
–35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
3
2
2
0
85°C
–40°C
–1
–2
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
Linearity Error vs RF Input Power,
880MHz Modulated Waveforms
3
1
5
5581 G06
2.0
LINEARITY ERROR (dB)
VOUT (V)
1.6
2.5
25°C
85°C
– 40°C
1
Linearity Error Temperature
Variation from 25°C at 880MHz
Output Voltage and Linearity Error
at 880MHz
1.8
CW
TETRA
CDMA 4C
5581 G05
5581 G04
2.0
TA = 25°C
–2
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
10
Linearity Error vs RF Input Power,
450MHz Modulated Waveforms
3
1
5
5581 G03
–2
–2.5
5
10MHz
450MHz
880MHz
2.14GHz
2.6GHz
3.5GHz
5.8GHz
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
2.0
VARIATION (dB)
1.8
–1
Linearity Error Temperature
Variation from 25°C at 450MHz
2.5
25°C
85°C
– 40°C
0
5581 G02
Output Voltage and Linearity Error
at 450MHz
2.0
1
–2
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
TA = 25°C
2
1.0
0.6
5
880MHz
2.14GHz
2.6GHz
3.5GHz
1.2
0.6
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
TA = 25°C
LINEARITY ERROR(dB)
VOUT (V)
1.4
1.8
Linearity Error vs Frequency
3
LINEARITY ERROR(dB)
1.6
TA = 25°C
VOUT (V)
1.8
Output Voltage vs Frequency
2.0
LINEARITY ERROR (dB)
Output Voltage vs Frequency
2.0
TA = 25°C
CW
EDGE
1
0
–1
–2
5
10
5581 G08
–3
–35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
10
5581 G09
5581f
5
LT5581
TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage and Linearity Error
at 2140MHz
3
2
2
1.0
1.2
0.5
1.0
0
0.8
–0.5
0.6
–1.0
0.4
–1.5
0.2
–2.0
85°C
0
–40°C
–1
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
5
5581 G10
1.4
1.0
1.2
0.5
1.0
0
0.8
–0.5
0.6
–1.0
0.4
–1.5
0.2
–2.0
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
3
2
2
85°C
–40°C
–1
–2
–2.5
5
0
5581 G13
1.5
1.4
1.0
1.2
0.5
1.0
0
0.8
–0.5
0.6
–1.0
0.4
–1.5
0.2
–2.0
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
–2.5
5
10
5581 G16
CW
WiMax OFDM PREAMBLE
WiMax OFDM BURST
WiMax OFDMA PREAMBLE
–3
–35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
3
2
2
0
85°C
–40°C
–1
5
10
5581 G17
TA = 25°C
1
0
–1
–2
–2
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
Linearity Error vs RF Input Power,
3.5GHz Modulated Waveforms
3
1
5
5581 G15
2.0
LINEARITY ERROR (dB)
VOUT (V)
1.6
2.5
25°C
85°C
– 40°C
–1
Linearity Error Temperature
Variation from 25°C at 3500MHz
VARIATION (dB)
1.8
0
5581 G14
Output Voltage and Linearity Error
at 3500MHz
2.0
5
TA = 25°C
1
–2
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
10
Linearity Error vs RF Input Power,
2.6GHz Modulated Waveforms
3
1
5
5581 G12
LINEARITY ERROR (dB)
1.5
LINEARITY ERROR (dB)
VOUT (V)
1.6
CW
WCDMA, UL
WCDMA DL 1C
WCDMA DL 4C
LTE DL 1C
LTE DL 4C
–3
–35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
2.0
VARIATION (dB)
1.8
–1
Linearity Error Temperature
Variation from 25°C at 2600MHz
2.5
25°C
85°C
– 40°C
0
5581 G11
Output Voltage and Linearity Error
at 2600MHz
2.0
TA = 25°C
1
–2
–2
–2.5
5
1
LINEARITY ERROR (dB)
1.5
1.4
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
3
2.0
LINEARITY ERROR (dB)
VOUT (V)
1.6
2.5
25°C
85°C
– 40°C
Linearity Error vs RF Input Power,
2140MHz Modulated Waveforms
LINEARITY ERROR (dB)
1.8
VARIATION (dB)
2.0
Linearity Error Temperature
Variation from 25°C at 2140MHz
CW
WiMax OFDMA PREAMBLE
WiMax OFDM BURST
–3
–35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
10
5581 G18
5581f
6
LT5581
TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage and Linearity Error
at 5800MHz
1.5
0.5
1.0
0
0.8
–0.5
0.6
–1.0
0.4
–1.5
0.2
–2.0
LINEARITY ERROR (dB)
1.0
1.2
3
2
2
1
85°C
0
–40°C
–1
–2
–2.5
5
3
5
Supply Current vs Supply Voltage
1.8
28
SUPPLY CURRENT (mA)
DISTRIBUTION (%)
30
30
20
10
26
5
6
28
29
30
31
32
SLOPE (mV/dB)
33
1.4
–40°C
1.2
34
0.8
2.6
3
3.4
3.8
5581 G23
Logarithmic Intercept
vs Frequency
4.2
4.6
5
5.4
5581 G24
Logarithmic Intercept Distribution
vs Temperature
50
TA = 25°C
TA = –40°C
TA = 25°C
TA = 85°C
40
–35
DISTRIBUTION (%)
LOGARITHMIC INTERCEPT (dBm)
25°C
SUPPLY VOLTAGE (V)
5581 G22
–30
85°C
1.6
1.0
0
2
3
4
FREQUENCY (GHz)
10
5581 G21
TA = –40°C
TA = 25°C
TA = 85°C
40
5
2.0
32
SLOPE (mV/dB)
–3
–35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
Slope Distribution vs Temperature
50
TA = 25°C
1
–1
5581 G20
Slope vs Frequency
0
0
CW
WiMax OFDM BURST
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
1
–2
5581 G19
34
TA = 25°C
2.0
1.4
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
Linearity Error vs RF Input Power,
5.8GHz Modulated Waveforms
LINEARITY ERROR (dB)
1.6
VOUT (V)
2.5
25°C
85°C
– 40°C
1.8
VARIATION (dB)
2.0
Linearity Error Temperature
Variation from 25°C at 5800MHz
–40
–45
30
20
10
0
–50
0
1
2
3
4
FREQUENCY (GHz)
6
5
5581 G25
–48
–47 –46 –45 –44 –43 –42
LOGARITHMIC INTERCEPT (dBm)
–41
5581 G26
5581f
7
LT5581
TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage and Linearity Error
vs VCC at 2140MHz
Supply Current vs RF Input Power
16
2.0
TA = 25°C
14
VOUT (V)
SUPPLY CURRENT (mA)
8
6
4
2
0
–25 –20 –15 –10 –5
0
5
RF INPUT POWER (dBm)
10
1.0
1.2
0.5
1.0
0
0.8
–0.5
0.6
–1.0
0.4
–1.5
0.2
–2.0
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
15
3.0
TA = 25°C
OUTPUT VOLTAGE (V)
–10
–15
–20
–25
10
TA = 25°C, VCC = 5V
2.5 RF & EN
PULSE
OFF
2.0
RF & EN PULSE ON
RF & EN
PULSE
OFF
5
0
PIN = 10dBm
PIN = 0dBm
1.5
–5
PIN = –10dBm
1.0
–10
PIN = –20dBm
PIN = –30dBm
0.5
–15
0
–20
–0.5
5
6
2
3
4
FREQUENCY (GHz)
L1, C1 = 2.2nH, 1.5pF
L1, C1 = 0nH, 0.5pF
L1, C1 = 1nH, 1.5pF
L1, C1 = 0nH, 0pF
L1, C1 = 0nH, 1pF
5581 G29
0
PIN = 0dBm
–10
PIN = –20dBm
0
0
2.0
2
0
1.5
PIN = 0dBm
–2
1.0
PIN = –10dBm
–4
PIN = –20dBm
0.5
0
–20
10 20 30 40 50 60 70 80 90 100
TIME (μs)
–0.5
5581 G31
EN
PULSE
OFF
PIN = 10dBm
–15
PIN = –30dBm
EN
PULSE
OFF
EN PULSE ON
ENABLE (V)
–5
OUTPUT VOLTAGE (V)
0
4
TA = 25°C
2.5
5
RF PULSE ENABLE (V)
RF
PULSE
OFF
PIN = –10dBm
0.5
3.0
10
PIN = 10dBm
1.0
1
Output Transient Response with
CW RF and EN Pulse
3.0
1.5
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
TIME (ms)
5581 G30
Output Transient Response
TA = 25°C, VCC = 5V
RF PULSE ON
RF
2.5 PULSE
OFF
2.0
–25
0
1
RF PULSE ENABLE (V)
RETURN LOSS (dB)
–5
OUTPUT VOLTAGE (V)
10
Output Transient Response with
RF and EN Pulse
Return Loss vs Frequency
Reference in Figure 1 Test Circuit
–30
–2.5
5
5581 G28
5581 G27
0
1.5
1.4
LINEARITY ERROR (dB)
10
2.0
3.3V
5V
1.6
12
2.5
TA = 25°C
1.8
–6
PIN = –30dBm
–8
–10
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
TIME (ms)
1
5581 G32
5581f
8
LT5581
PIN FUNCTIONS
V CC (Pin 1): Power Supply, 2.7V to 5.25V. V CC
should be bypassed with a 0.1μF ceramic capacitor.
EN (Pin 2): Chip Enable. A logic low or no-connect on the
enable pin shuts down the part. A logic high enables the
part. An internal 500k pull-down resistor ensures the part is
off when the enable driver is in a three-state condition.
VOUT (Pin 3): Detector Output.
GND (Pins 4, 5, 6): Ground.
CSQ (Pin 8): Optional Low Frequency Range Extension
Capacitor. This pin is for frequencies below 250MHz. Use
0.01μF from pin to ground for 10MHz operation.
Exposed Pad (Pin 9): Ground. The Exposed Pad must
be soldered to the PCB. For high frequency operation, the backside ground connection should have a low
inductance connection to the PCB ground, using many
through-hole vias. See the layout information in the Applications Information section.
RFIN (Pin 7): RF Input. Should be DC-blocked with coupling
capacitor; 1000pF recommended. This pin has an internal
200Ω termination.
BLOCK DIAGRAM
9
LT5581
EXPOSED
PAD
OUTPUT
BUFFER
150kHz LPF
7
RFIN
300Ω
RMS
DETECTOR
BIAS
CSQ
8
3
GND
EN
2
VOUT
VCC
1
4
5
6
5581 BD
5581f
9
LT5581
TEST CIRCUIT
C7
0.1μF
VCC
C6
100pF
C3
0.01μF
C5
OPT
1
EN
2
R3
0Ω
VOUT
C4
OPT
3
NC
4
CSQ
VCC
EN
LT5581
GND
VOUT
GND
RFIN
GND
GND
8
C2
1000pF
L1
2.2nH
7
6
5
NC
R2
68Ω
RFIN
C1
1.5pF
NC
9
PINS 4, 5, 6: OPTIONAL GROUND
0.018"
EE = 4.4
5581 F01
RF
GND
0.062"
0.018"
DC
GND
REF DES
VALUE
SIZE
PART NUMBER
C6
100pF
0603
AVX 06033A101KAT2A
FREQUENCY
RANGE
L1
C1
C7
0.1μF
0603
AVX 06033C104KAT2A
1GHz to 2.2GHz
2.2nH
1.5pF
C3
0.01μF
0603
AVX 06033C103KAT2A
2GHz to 2.6GHz
1.2nH
1.5pF
AVX 06033C102KAT2A
2.6GHz to 3.4GHz
0
1pF
3.8GHz to 5.5GHz
0
0.5pF
4.6GHz to 6GHz
0
0
C2
1000pF
0603
R2
68Ω
0603
RFIN MATCH
Figure 1. Evaluation Circuit Schematic
5581f
10
LT5581
APPLICATIONS INFORMATION
OPERATION
Table 1. RF Input Impedance
To achieve an accurate average power measurement of
the high crest factor modulated RF signals, the LT5581
combines a proprietary high speed power measurement
subsystem with an internal 150kHz low pass averaging filter and an output voltage buffer in a completely
integrated solution with minimal off-chip components.
The resulting output voltage is directly proportional to
the average RF input power in dBm. Figure 1 shows the
evaluation circuit schematic, and Figures 2 and 3 show
the associated board artwork. For best high frequency
performance, it is important to place many ground vias
directly under the package.
FREQUENCY
(MHz)
INPUT
IMPEDANCE
(Ω)
MAG
ANGLE (°)
10
203.6-j5.5
0.606
–0.8
S11
50
199.5-j22.4
0.603
–3.4
100
191.7-j40.3
0.601
–6.4
200
171.1-j68.5
0.601
–12.3
400
121.8-j95.4
0.608
–24
500
100.2-j97.5
0.613
–29.8
800
56.8-j86.5
0.631
–46.5
900
48-j81.2
0.638
–51.8
1000
41.1-j76
0.645
–56.8
1500
22.2-j55
0.679
–79.5
RF Input Matching
2000
14.6-j41.4
0.710
–97.9
The input resistance is about 205Ω. Input capacitance
is 1.6pF. The impedance vs frequency of the RF input is
detailed in Table 1.
2100
13.6-j39.2
0.716
–101.2
2500
10.8-j32.1
0.737
–112.9
5581 F02
Figure 2. Top Side of Evaluation Board
3000
8.6-j25
0.759
–125.7
3500
7.3-j19.4
0.774
–136.9
4000
6.6-j14.5
0.783
–147.1
5000
8.8-j9.6
0.709
–157.6
6000
6.4-j0
0.774
–179.9
5581 F03
Figure 3. Bottom Side of Evaluation Board
5581f
11
LT5581
APPLICATIONS INFORMATION
A shunt 68Ω resistor can be used to provide a broadband
impedance match at low frequencies up to 1.3GHz, and
from 4.5GHz to 6GHz. As shown in Figure 4, a nominal
broadband input match can be achieved up to 2.2GHz by
using an LC matching circuit consisting of a series 2.2nH
inductor (L1) and a shunt 1.5pF capacitor (C1). This
match will maintain a return loss of about 10dB across
the band. For matching at higher frequencies, values for
L1 and C1 are listed in the table of Figure 1. The input
reflection coefficient referenced to the RF input pin (with
no external components) is shown on the Smith Chart
in Figure 5. Alternatively, it is possible to match using
an impedance transformation network by omitting R1
and transforming the 205Ω load to 50Ω. The resulting
match, over a narrow band of frequencies, will improve
sensitivity up to about 6dB maximum; the dynamic range
remains the same. For example, by omitting R1 and setting L1 = 1.8nH and C1 = 3pF, a 2:1 VSWR match can
be obtained from 1.95GHz to 2.36GHz, with a sensitivity
improvement of 5dB.
The RFIN input DC blocking capacitor (C2) and the CSQ
bias decoupling capacitor (C3), can be adjusted for low
VCC
frequency operation. For input frequencies down to 10MHz,
0.01μF is needed at CSQ. For frequencies above 250MHz,
the on-chip 20pF decoupling capacitor is sufficient, and
CSQ may be eliminated as desired. The DC-blocking capacitor can be as large as 2200pF for 10MHz operation, or
100pF for 2GHz operation. A DC-blocking capacitor larger
than 2200pF results in an undesirable RF pulse response
on the falling edge. Therefore, for general applications,
the recommended value for C2, is conservatively set at
1000pF.
Output Interface
The output buffer of the LT5581 is shown in Figure 6. It
includes a push-pull stage with a series 300Ω resistor.
The output stage is capable of sourcing and sinking 5mA
of current. The output pin can be shorted to GND or VCC
without damage, but going beyond VCC + 0.5V or GND
– 0.5V may result in damage, as the internal ESD protection
diodes will start to conduct excessive current.
The residual ripple, due to RF modulation, can be reduced
by adding external components RSS and CLOAD (R3 and
C4 on the Evaluation Circuit Schematic in Figure 1) to
LT5581
C3
0.01μF
8
RFIN
(MATCHED)
L1
205Ω
C2
1000pF
7
C1
CSQ
20pF
RFIN
R1
68Ω
5581 F04
Figure 4. Simplified Circuit Schematic of the RF Input Interface
Figure 5. Input Reflection Coefficient
5581f
12
LT5581
APPLICATIONS INFORMATION
the output pin, to form an RC lowpass filter. The internal
300Ω resistor in series with the output pin enables filtering of the output signal with just the addition of CLOAD.
Figure 7 shows the effect of the external filter capacitor
on the residual ripple level for a 4-carrier WCDMA signal
at 2.14GHz with –10dBm. Adding a 10nF capacitor to the
output decreases the peak-to-peak output ripple from
135mVP-P to 50mVP-P. The filter –3dB corner frequency
can be calculated with the following equation:
1
fC =
2π CLOAD(300 + R SS )
of 3, using a 0.047μF external filter capacitor. The average power in the preamble section is –10dBm, while the
burst section has a 3dB lower average power. With the
capacitor, the ripple in the preamble section is about 0.5dB
peak-to-peak. The modulation used was OFDM (WiMAX
802.16-2004) MMDS band, 1.5MHz BW, with 256 size FFT
and 1 burst at QPSK 3/4.
Figure 9 shows how the peak-to-peak ripple decreases with
increasing external filter capacitance value. Also shown is
how the RF pulse response will have longer rise and fall
times with the addition of this lowpass filter cap.
Figure 8 shows the transient response for a 2.6GHz WiMAX
signal, with preamble and burst ripple reduced by a factor
1.4
LT5581
NO CAP
0.01μF
RSS
VOUT
(FILTERED)
3
1.20
1.0
1.15
0.8
1.10
0.6
1.05
0.4
1.00
0.2
0.95
OUTPUT VOLTAGE (V)
300Ω
INPUT
VOUT
OUTPUT VOLTAGE (V)
1.2
40μA
1.25
TA = 25°C
VCC
5581 F06
CLOAD
Figure 6. Simplified Circuit Schematic of the Output Interface
0
1.0
0.8
0.6
0.4
0.2
0
0
0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
TIME (ms)
5581 F08
Figure 8. Residual Ripple for 2.6GHz WiMAX OFDM 802.16-2004
8
RIPPLE
RISE
FALL
1000
TA = 25°C
7
100
6
5
4
3
10
2
RISE TIME AND FALL TIME (μs)
1.2
NO CAP
0.047μF
OUTPUT RIPPLE PEAK-TO-PEAK (dB)
TA = 25°C
0.90
10 20 30 40 50 60 70 80 90 100
TIME (μs)
5581 F07
Figure 7. Residual Ripple, Output Transient Response
for RF Pulse with WCDMA 4-Carrier Modulation
9
1.4
OUTPUT VOLTAGE (V)
0
1
0
0.001
1
0.01
0.1
EXTERNAL CAPACITOR (μF)
1
5581 F09
Figure 9. Residual Ripple, Output Transient Times for RF Pulse
with WCDMA 4-Carrier Modulation vs External Filter Capacitor C4
5581f
13
LT5581
APPLICATIONS INFORMATION
Figure 10 shows that rise time and fall time are strong
functions of RF input power. Data is taken without the
output filter capacitor.
For a given RF modulation type—WCDMA, for example—the internal 150kHz filter provides nominal filtering
of the residual ripple level. Additional external filtering
occurs in the log domain, which introduces a systematic
log error in relation to the signal’s crest factor, as shown
in the following equation in dB.1
Error|dB = 10 • log10(r + (1 – r)10–CF/10) – CF • (r-1)
Where CF is the crest factor and r is the duty cycle of the
measurement (or number of measurements made at the
peak envelope, divided by the total number of periodic
measurements in the measurement period). It is important to note that the CF refers to the 150kHz low pass
filtered envelope of the signal. The error will depend on
the statistics and bandwidth of the modulation signal in
relation to the internal 150kHz filter. For example, in the
case of WCDMA, simulations prove that it is possible to
set the external filter capacitor corner frequency at 15kHz
and only introduce an error less than 0.1dB.
Figure 11 depicts the output AM modulation ripple as a
function of modulation difference frequency for a 2-tone
input signal at 2140MHz with –10dBm input power. The
1 Steve Murray, “Beware of Spectrum Analyzer Power Averaging Techniques,” Microwaves
& RF, Dec. 2006.
9
30
TA = 25°C
RISE TIME AND FALL TIME (μs)
FALL TIME
OUTPUT AC RIPPLE (dB)
7
6
5
4
3
2
RISE TIME
1
0
–30
–25
–20
–15
–10
–5
0
25
–0.5
20
–1.0
15
–1.5
10
–2.0
5
–2.5
0
0.001
5
INPUT POWER (dBm)
–3.0
0.01
0.1
10
1
2-TONE FREQUENCY SEPARATION (MHz)
5581 F10
Figure 10. RF Pulse Response Rise Time
and Fall Time vs RF Input Power
4.0
5581 F11
Figure 11. Output DC Voltage Deviation and Residual
Ripple vs 2-Tone Separation Frequency
2.0
TA = 25°C
1.8
INTEGRATED NOISE (mVRMS)
NOISE VOLTAGE (μVRMS / Hz)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0.1
0dBm
–10dBm
–20dBm
–30dBm
NO RF INPUT
1
100
10
FREQUENCY (kHz)
DEVIATION OF OUTPUT VOLTAGE (dB)
8
0
TA = 25°C
TA = 25°C
1.6
1.4
1.2
0dBm
–10dBm
–20dBm
–30dBm
NO RF INPUT
1.0
0.8
0.6
0.4
0.2
1000
5581 F12
Figure 12. Output Voltage Noise Density
0
0.1
1
100
10
FREQUENCY (kHz)
1000
5581 F13
Figure 13. Integrated Output Voltage Noise
5581f
14
LT5581
APPLICATIONS INFORMATION
resulting deviation in the output voltage of the detector
shows the effect of the internal 150kHz filter.
The output voltage noise density and integrated noise are
shown in Figures 12 and 13, respectively, for various input
power levels. Noise is a strong function of input level. There
is roughly a 10dB reduction in the output noise level for
an input level of 0dBm versus no input.
It is important that the voltage applied to the EN pin never
exceeds VCC by more than 0.5V, otherwise, the supply
current may be sourced through the upper ESD protection
diode connected at the EN pin.
VCC
LT5581
2
EN
Enable Pin
500k
A simplified schematic of the EN pin is shown in Figure
14. To enable the LT5581, it is necessary to put greater
than 1V on this pin. To disable or turn off the chip, this
voltage should be below 0.3V. At an enable voltage of
3.3V, the pin draws roughly 20μA. If the EN pin is not
connected, the chip is disabled through an internal 500k
pull-down resistor.
300k
300k
5581 F14
Figure 14. Enable Pin Simplified Schematic
PACKAGE DESCRIPTION
DDB Package
8-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1702 Rev B)
0.61 ±0.05
(2 SIDES)
3.00 ±0.10
(2 SIDES)
R = 0.115
TYP
5
R = 0.05
TYP
0.40 ± 0.10
8
0.70 ±0.05
2.55 ±0.05
1.15 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.200 REF
0.50 BSC
2.20 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
2.00 ±0.10
(2 SIDES)
0.56 ± 0.05
(2 SIDES)
0.75 ±0.05
0 – 0.05
4
0.25 ± 0.05
1
PIN 1
R = 0.20 OR
0.25 × 45°
CHAMFER
(DDB8) DFN 0905 REV B
0.50 BSC
2.15 ±0.05
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
5581f
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
15
LT5581
RELATED PARTS
PART NUMBER
DESCRIPTION
RF Power Detectors
LTC®5505
RF Power Detectors with >40dB Dynamic Range
LTC5507
100kHz to 1000MHz RF Power Detector
LTC5508
300MHz to 7GHz RF Power Detector
LTC5509
300MHz to 3GHz RF Power Detector
LTC5530
300MHz to 7GHz Precision RF Power Detector
LTC5531
300MHz to 7GHz Precision RF Power Detector
LTC5532
300MHz to 7GHz Precision RF Power Detector
LT5534
50MHz to 3GHz Log RF Power Detector with
60dB Dynamic Range
LTC5536
Precision 600MHz to 7GHz RF Power Detector
with Fast Comparator Output
LT5537
Wide Dynamic Range Log RF/IF Detector
LT5538
75dB Dynamic Range 3.8GHz Log RF Power
Detector
LT5570
60dB Dynamic Range RMS Detector
Infrastructure
LT5514
Ultralow Distortion, IF Amplifier/ADC Driver
with Digitally Controlled Gain
LT5517
40MHz to 900MHz Quadrature Demodulator
LT5518
1.5GHz to 2.4GHz High Linearity Direct
Quadrature Modulator
COMMENTS
LT5519
0.7GHz to 1.4GHz High Linearity Upconverting
Mixer
17.1dBm IIP3 at 1GHz, Integrated RF Output Transformer with 50Ω Matching,
Single-Ended LO and RF Ports Operation
LT5520
1.3GHz to 2.3GHz High Linearity Upconverting
Mixer
LT5521
10MHz to 3700MHz High Linearity
Upconverting Mixer
600MHz to 2.7GHz High Signal Level
Downconverting Mixer
15.9dBm IIP3 at 1.9GHz, Integrated RF Output Transformer with 50Ω Matching,
Single-Ended LO and RF Ports Operation
24.2dBm IIP3 at 1.95GHz, NF = 12.5dB, 3.15V to 5.25V Supply, Single-Ended LO
Port Operation
LT5522
LT5525
LT5526
LT5527
LT5528
LT5557
LT5560
LT5568
LT5572
LT5575
High Linearity, Low Power Downconverting
Mixer
High Linearity, Low Power Downconverting
Mixer
400MHz to 3.7GHz High Signal Level
Downconverting Mixer
1.5GHz to 2.4GHz High Linearity Direct
Quadrature Modulator
400MHz to 3.8GHz, 3.3V High Signal Level
Downconverting Mixer
Ultralow Power Active Mixer
700MHz to 1050MHz High Linearity Direct
Quadrature Modulator
1.5GHz to 2.5GHz High Linearity Direct
Quadrature Modulator
800MHz to 2.7GHz High Linearity Direct
Conversion I/Q Demodulator
300MHz to 3GHz, Temperature Compensated, 2.7V to 6V Supply
100kHz to 1GHz, Temperature Compensated, 2.7V to 6V Supply
44dB Dynamic Range, Temperature Compensated, SC70 Package
36dB Dynamic Range, Low Power Consumption, SC70 Package
Precision VOUT Offset Control, Shutdown, Adjustable Gain
Precision VOUT Offset Control, Shutdown, Adjustable Offset
Precision VOUT Offset Control, Adjustable Gain and Offset
±1dB Output Variation over Temperature, 38ns Response Time, Log Linear
Response
25ns Response Time, Comparator Reference Input, Latch Enable Input,
–26dBm to +12dBm Input Range
Low Frequency to 1GHz, 83dB Log Linear Dynamic Range
±0.8dB Accuracy Over Temperature
40MHz to 2.7GHz, ±0.5dB Accuracy Over Temperature
850MHz Bandwidth, 47dBm OIP3 at 100MHz, 10.5dB to 33dB Gain Control Range
21dBm IIP3, Integrated LO Quadrature Generator
22.8dBm OIP3 at 2GHz, –158.2dBm/Hz Noise Floor, 50Ω Single-Ended RF and LO
Ports, 4-Channel W-CDMA ACPR = –64dBc at 2.14GHz
4.5V to 5.25V Supply, 25dBm IIP3 at 900MHz, NF = 12.5dB, 50Ω Single-Ended RF
and LO Ports
Single-Ended 50Ω RF and LO Ports, 17.6dBm IIP3 at 1900MHz, ICC = 28mA
3V to 5.3V Supply, 16.5dBm IIP3, 100kHz to 2GHz RF, NF = 11dB, ICC = 28mA,
–65dBm LO-RF Leakage
IIP3 = 23.5dBm and NF = 12.5dBm at 1900MHz, 4.5V to 5.25V Supply, ICC = 78mA,
Conversion Gain = 2dB
21.8dBm OIP3 at 2GHz, –159.3dBm/Hz Noise Floor, 50Ω, 0.5VDC Baseband
Interface, 4-Channel W-CDMA ACPR = –66dBc at 2.14GHz
IIP3 = 23.7dBm at 2600MHz, 23.5dBm at 3600MHz, ICC = 82mA at 3.3V
10mA Supply Current, 10dBm IIP3, 10dB NF, Usable as Up- or Down-Converter.
22.9dBm OIP3 at 850MHz, –160.3dBm/Hz Noise Floor, 50Ω, 0.5VDC Baseband
Interface, 3-Ch CDMA2000 ACPR = –71.4dBc at 850MHz
21.6dBm OIP3 at 2GHz, –158.6dBm/Hz Noise Floor, High-Ohmic 0.5VDC Baseband
Interface, 4-Ch W-CDMA ACPR = –67.7dBc at 2.14GHz
50Ω, Single-Ended RF and LO Inputs. 28dBm IIP3 at 900MHz, 13.2dBm P1dB,
0.04dB I/Q Gain Mismatch, 0.4° I/Q Phase Mismatch
5581f
16 Linear Technology Corporation
LT 0708 • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2008