LT5581
6GHz RMS Power Detector
with 40dB Dynamic Range
FEATURES
DESCRIPTION
Frequency Range: 10MHz to 6GHz
nn Accurate Power Measurement of High Crest Factor
(Up to 12dB) Waveforms
nn 40dB Log Linear Dynamic Range
nn Exceptional Accuracy Over Temperature
nn Fast Response Time: 1μs Rise, 8μs Fall
nn Low Power: 1.4mA at 3.3V
nn Log-Linear DC Output vs Input RF Power in dBm
nn Small 3mm × 2mm 8-Pin DFN Package
nn Single-Ended RF Input
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,
TD-SCDMA, 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.
nn
APPLICATIONS
GSM/EDGE, CMDA, CDMA2000, W-CDMA, LTE,
WiMAX RF Power Control
nn Pico-Cells, Femto-Cells RF Power Control
nn Wireless Repeaters
nn CATV/DVB Transmitters
nn MIMO Wireless Access Points
nn Portable RMS Power Measurement Instrumentation
nn
L, LT, LTC, LTM, Linear Technology and the Linear logo 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
VCC
2.7VDC TO 5.25VDC
0.1µF
DIGITAL
POWER
CONTROL
1
2
ADC
CFILT
0.01µF
3
4
EN
LT5581
GND
VOUT
GND
RFIN
GND
GND
0.01µF
8
7
50Ω
LMATCH
1000pF
6
5
TA = 25°C
2
CMATCH
CSQ
VCC
3
RFOUT
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
5581fb
For more information www.linear.com/LT5581
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 × 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
2
5581fb
For more information www.linear.com/LT5581
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
5581fb
For more information www.linear.com/LT5581
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
5/5
mA
Rise Time
Output Current Sourcing/Sinking
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
Supply Voltage
l
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 functional over the operating
temperature range 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.
4
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.
5581fb
For more information www.linear.com/LT5581
LT5581
TYPICAL
PERFORMANCE CHARACTERISTICS
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
1.2
0.6
0.4
0.2
0.2
5
5581 G01
2.5
25°C
85°C
– 40°C
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)
5
2
2
10
0
85°C
–40°C
–1
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
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
5
10
5581 G07
–2.5
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
10
Linearity Error vs RF Input Power,
880MHz Modulated Waveforms
3
1
5
5581 G06
2.0
LINEARITY ERROR (dB)
VOUT (V)
1.6
1
Linearity Error Temperature
Variation from 25°C at 880MHz
2.5
25°C
85°C
– 40°C
CW
TETRA
CDMA 4C
5581 G05
Output Voltage and Linearity Error
at 880MHz
1.8
TA = 25°C
–2
–2
–2.5
10
Linearity Error vs RF Input Power,
450MHz Modulated Waveforms
3
1
5
5581 G03
3
5581 G04
2.0
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
LINEARITY ERROR (dB)
VOUT (V)
1.6
–1
Linearity Error Temperature
Variation from 25°C at 450MHz
VARIATION (dB)
1.8
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
0.8
0.4
5
880MHz
2.14GHz
2.6GHz
3.5GHz
1.0
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
Performance characteristics taken at VCC = 3.3V,
85°C
–40°C
–1
TA = 25°C
CW
EDGE
1
0
–1
–2
–2
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
10
5581 G08
–3
–35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
5
10
5581 G09
5581fb
For more information www.linear.com/LT5581
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
5
10
1
0
–2.5
0.5
1.0
0
0.8
–0.5
3
2
2
0.6
–1.0
0.4
–1.5
0.2
–2.0
10
0
85°C
–40°C
–1
–2
–2.5
5581 G13
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
5
10
5581 G16
6
–2.5
VARIATION (dB)
1.5
1.4
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
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
–1
Linearity Error Temperature
Variation from 25°C at 3500MHz
2.5
25°C
85°C
– 40°C
0
5581 G14
Output Voltage and Linearity Error
at 3500MHz
1.8
5
TA = 25°C
1
–2
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
Linearity Error vs RF Input Power,
2.6GHz Modulated Waveforms
3
1
5
5581 G12
LINEARITY ERROR (dB)
1.2
VARIATION (dB)
1.5
5
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
1.0
2.0
–1
Linearity Error Temperature
Variation from 25°C at 2600MHz
1.4
0
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
0
5581 G11
LINEARITY ERROR (dB)
VOUT (V)
1.6
5
TA = 25°C
1
–2
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
2.5
25°C
85°C
– 40°C
–40°C
–1
Output Voltage and Linearity Error
at 2600MHz
1.8
85°C
–2
5581 G10
2.0
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
Linearity Error vs RF Input Power,
2140MHz Modulated Waveforms
LINEARITY ERROR (dB)
1.8
2.5
25°C
85°C
– 40°C
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
5581fb
For more information www.linear.com/LT5581
LT5581
TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage and Linearity Error
at 5800MHz
1.6
1.5
0.5
1.0
0
0.8
–0.5
0.6
–1.0
0.4
–1.5
0.2
–2.0
10
LINEARITY ERROR (dB)
1.0
1.2
5
3
3
2
2
1
85°C
0
–40°C
–1
–2
–2.5
–3
–40 –35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
28
Supply Current vs Supply Voltage
1.8
20
28
29
30
31
32
SLOPE (mV/dB)
33
1.6
25°C
1.4
–40°C
1.2
34
0.8
2.6
3
3.4
3.8
4.2
4.6
5
5.4
SUPPLY VOLTAGE (V)
5581 G23
Logarithmic Intercept
vs Frequency
5581 G24
Logarithmic Intercept Distribution
vs Temperature
50
TA = 25°C
TA = 85°C
TA = 25°C
TA = –40°C
40
DISTRIBUTION (%)
–35
–40
–45
–50
85°C
1.0
5581 G22
–30
10
2.0
30
0
6
5
5
5581 G21
10
2
3
4
FREQUENCY (GHz)
CW
WiMax OFDM BURST
–3
–35 –30 –25 –20 –15 –10 –5 0
RF INPUT POWER (dBm)
10
SUPPLY CURRENT (mA)
DISTRIBUTION (%)
30
LOGARITHMIC INTERCEPT (dBm)
SLOPE (mV/dB)
5
TA = 85°C
TA = 25°C
TA = –40°C
40
32
1
–1
Slope Distribution vs Temperature
50
TA = 25°C
0
0
5581 G20
Slope vs Frequency
26
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)
1.8
VOUT (V)
2.5
25°C
85°C
– 40°C
VARIATION (dB)
2.0
Linearity Error Temperature
Variation from 25°C at 5800MHz
30
20
10
0
1
2
3
4
FREQUENCY (GHz)
6
5
0
–48
5581 G25
–47 –46 –45 –44 –43 –42
LOGARITHMIC INTERCEPT (dBm)
–41
5581 G26
5581fb
For more information www.linear.com/LT5581
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
1.8
12
VOUT (V)
10
8
6
4
2
0
0
5
–25 –20 –15 –10 –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)
RETURN LOSS (dB)
–15
–20
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
–0.5
2
3
4
5
6
FREQUENCY (GHz)
L1, C1 = 0nH, 0.5pF
L1, C1 = 2.2nH, 1.5pF
L1, C1 = 0nH, 0pF
L1, C1 = 1nH, 1.5pF
L1, C1 = 0nH, 1pF
5581 G29
1
–15
–10
PIN = –20dBm
2.0
EN PULSE ON
–25
4
TA = 25°C
EN
PULSE
OFF
2
0
PIN = 10dBm
1.5
PIN = 0dBm
–2
1.0
PIN = –10dBm
–4
0.5
PIN = –30dBm
–15
0
–20
10 20 30 40 50 60 70 80 90 100
TIME (µs)
–0.5
PIN = –30dBm
0
OUTPUT VOLTAGE (V)
–5
PIN = 0dBm
0.5
1
PIN = –20dBm
ENABLE (V)
0
EN
PULSE
OFF
2.5
5
RF PULSE ENABLE (V)
RF
PULSE
OFF
PIN = –10dBm
1.0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
TIME (ms)
3.0
10
PIN = 10dBm
1.5
0
Output Transient Response with
CW RF and EN Pulse
3.0
TA = 25°C, VCC = 5V
RF PULSE ON
RF
2.5 PULSE
OFF
2.0
–20
5581 G30
Output Transient Response
OUTPUT VOLTAGE (V)
10
TA = 25°C, VCC = 5V
0
0
–2.5
RF PULSE ENABLE (V)
–10
–25
–6
–8
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
TIME (ms)
5581 G31
8
10
Output Transient Response with
RF and EN Pulse
–5
0
5
5581 G28
Return Loss vs Frequency
Reference in Figure 1 Test Circuit
–30
1.5
1.4
5581 G27
0
2.0
3.3V
5V
1.6
LINEARITY ERROR (dB)
SUPPLY CURRENT (mA)
14
2.5
TA = 25°C
1
–10
5581 G32
5581fb
For more information www.linear.com/LT5581
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
7
EXPOSED
PAD
OUTPUT
BUFFER
150kHz LPF
RFIN
300Ω
RMS
DETECTOR
BIAS
2
3
GND
EN
CSQ
8
VOUT
VCC
1
4
5
6
5581 BD
5581fb
For more information www.linear.com/LT5581
9
LT5581
TEST CIRCUIT
C7
0.1µF
VCC
C6
100pF
C5
OPT
1
EN
2
R3
0Ω
VOUT
C4
OPT
3
NC
4
CSQ
VCC
EN
LT5581
GND
VOUT
GND
RFIN
GND
GND
8
C3
0.01µF
C2
1000pF
7
6
5
NC
L1
2.2nH
R2
68Ω
RFIN
C1
1.5pF
NC
9
0.018"
EE = 4.4
0.062"
0.018"
PINS 4, 5, 6: OPTIONAL GROUND
RF
GND
5581 F01
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
10
5581fb
For more information www.linear.com/LT5581
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
RF Input Matching
1500
22.2-j55
0.679
–79.5
The input resistance is about 205Ω. Input capacitance
is 1.6pF. The impedance vs frequency of the RF input is
detailed in Table 1.
2000
14.6-j41.4
0.710
–97.9
2100
13.6-j39.2
0.716
–101.2
2500
10.8-j32.1
0.737
–112.9
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 F02
Figure 2. Top Side of Evaluation Board
5581 F03
Figure 3. Bottom Side of Evaluation Board
5581fb
For more information www.linear.com/LT5581
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
12
Figure 5. Input Reflection Coefficient
5581fb
For more information www.linear.com/LT5581
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
f =
C
2π CLOAD (300 +RSS )
factor 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
1.4
LT5581
VCC
RSS
3
VOUT
(FILTERED)
OUTPUT VOLTAGE (V)
VOUT
5581 F06
CLOAD
TA = 25°C
OUTPUT VOLTAGE (V)
NO CAP
0.047µF
1.0
0.8
0.6
0.4
0.2
0
0
0.8
1.10
0.6
1.05
0.4
1.00
0.2
0.95
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
0
0.90
10 20 30 40 50 60 70 80 90 100
TIME (µs)
5581 F07
9
8
7
RIPPLE
RISE
FALL
1000
TA = 25°C
100
6
5
4
10
3
2
RISE TIME AND FALL TIME (µs)
1.2
1.15
Figure 7. Residual Ripple, Output Transient Response
for RF Pulse with WCDMA 4-Carrier Modulation
OUTPUT RIPPLE PEAK-TO-PEAK (dB)
1.4
1.0
0
Figure 6. Simplified Circuit Schematic of the Output Interface
1.20
OUTPUT VOLTAGE (V)
300Ω
INPUT
NO CAP
0.01µF
1.2
40µA
1.25
TA = 25°C
1
0
0.001
0.01
0.1
EXTERNAL CAPACITOR (µF)
1
1
5581 F09
Figure 9. Residual Ripple, Output Transient Times for RF Pulse
with WCDMA 4-Carrier Modulation vs External Filter Capacitor C4
5581fb
For more information www.linear.com/LT5581
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
9
1 Steve Murray, “Beware of Spectrum Analyzer Power Averaging Techniques,” Microwaves
& RF, Dec. 2006.
30
TA = 25°C
FALL TIME
7
OUTPUT AC RIPPLE (dB)
RISE TIME AND FALL TIME (µs)
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
resulting deviation in the output voltage of the detector
shows the effect of the internal 150kHz filter.
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
0
TA = 25°C
INPUT POWER (dBm)
0.01
0.1
10
1
2-TONE FREQUENCY SEPARATION (MHz)
4.0
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)
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
0
0.1
1
100
10
FREQUENCY (kHz)
1000
5581 F13
5581 F12
Figure 12. Output Voltage Noise Density
14
–3.0
5581 F11
5581 F10
Figure 10. RF Pulse Response Rise Time
and Fall Time vs RF Input Power
DEVIATION OF OUTPUT VOLTAGE (dB)
8
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 13. Integrated Output Voltage Noise
5581fb
For more information www.linear.com/LT5581
LT5581
APPLICATIONS INFORMATION
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
Enable Pin
A simplified schematic of the EN pin is shown in Figure 14.
To enable the LT5581, it is necessary to put greater than
2V 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.
2
EN
500k
300k
300k
5581 F14
Figure 14. Enable Pin Simplified Schematic
5581fb
For more information www.linear.com/LT5581
15
LT5581
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
DDB Package
8-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1702 Rev B)
0.61 ±0.05
(2 SIDES)
0.70 ±0.05
2.55 ±0.05
1.15 ±0.05
PACKAGE
OUTLINE
0.25 ±0.05
0.50 BSC
2.20 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
3.00 ±0.10
(2 SIDES)
R = 0.115
TYP
5
R = 0.05
TYP
0.40 ±0.10
8
2.00 ±0.10
(2 SIDES)
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.56 ±0.05
(2 SIDES)
0.200 REF
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
16
5581fb
For more information www.linear.com/LT5581
LT5581
REVISION HISTORY
REV
DATE
DESCRIPTION
A
4/10
Updated Note 2 in Electrical Characteristics Section
PAGE NUMBER
4
B
8/15
Changed Enable Pin input voltage to 2V
15
5581fb
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 interconnectionFor
of its
circuits
as described
herein will not infringe on existing patent rights.
more
information
www.linear.com/LT5581
17
LT5581
RELATED PARTS
PART NUMBER
DESCRIPTION
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LTC5507
100kHz to 1000MHz RF Power Detector
LTC5508
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LTC5509
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LTC5530
300MHz to 7GHz Precision RF Power Detector
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300MHz to 7GHz Precision RF Power Detector
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50MHz to 3GHz Log RF Power Detector with
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Wide Dynamic Range Log RF/IF Detector
LT5538
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Ultralow Distortion, IF Amplifier/ADC Driver
with Digitally Controlled Gain
LT5517
40MHz to 900MHz Quadrature Demodulator
LT5519
0.7GHz to 1.4GHz High Linearity Upconverting
Mixer
LT5520
1.3GHz to 2.3GHz High Linearity Upconverting
Mixer
LT5521
10MHz to 3700MHz High Linearity
Upconverting Mixer
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600MHz to 2.7GHz High Signal Level
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LT5525
High Linearity, Low Power Downconverting
Mixer
LT5526
High Linearity, Low Power Downconverting
Mixer
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400MHz to 3.7GHz High Signal Level
Downconverting Mixer
LT5557
400MHz to 3.8GHz, 3.3V High Signal Level
Downconverting Mixer
LT5560
Ultralow Power Active Mixer
LT5568
700MHz to 1050MHz High Linearity Direct
Quadrature Modulator
LT5572
1.5GHz to 2.5GHz High Linearity Direct
Quadrature Modulator
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800MHz to 2.7GHz High Linearity Direct
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18 Linear Technology Corporation
COMMENTS
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
850MHz Bandwidth, 47dBm OIP3 at 100MHz, 10.5dB to 33dB Gain Control Range
21dBm IIP3, Integrated LO Quadrature Generator
17.1dBm IIP3 at 1GHz, Integrated RF Output Transformer with 50Ω Matching,
Single-Ended LO and RF Ports Operation
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
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
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
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LT5581
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LT5581
5581fb
LT 0815 REV B • PRINTED IN USA
LINEAR TECHNOLOGY CORPORATION 2008
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