Document
LT5581
6GHz RMS Power Detector with 40dB Dynamic Range
FEATURES
n Frequency Range: 10MHz to 6GHz n Accurate Power Measurement of High Crest Factor
(Up to 12dB) Waveforms n 40dB Log Linear Dynamic Range n Exceptional Accuracy Over Temperature n Fast Response Time: 1μs Rise, 8μs Fall n Low Power: 1.4mA at 3.3V n Log-Linear DC Output vs Input RF Power in dBm n Small 3mm × 2mm 8-Pin DFN Package n Single-Ended RF Input
APPLICATIONS
n GSM/EDGE, CMDA, CDMA2000, W-CDMA, LTE, WiMAX RF Power Control
n Pico-Cells, Femto-Cells RF Power Control n Wireless Repeaters n CATV/DVB Transmitters n MIMO Wireless Access Points n Portable RMS Power Measurement Instrumentation
DESCRIPTION
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.
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
POWER RFIN AMP
DIRECTIONAL
COUPLER RFOUT
DIGITAL POWER CONTROL
0.1μF
ADC CFILT
0.01μF
VCC 2.7VDC TO 5.25VDC
0.01μF
1 VCC
8 CSQ
1000pF
2 EN LT5581 RFIN 7
3 VOUT
GND 6
4 GND GND GND 5
9
CMATCH LMATCH
50Ω
68Ω
5581 TA01a
LINEARITY ERROR (dB)
Linearity Error vs RF Input Power, 2140MHz Modulated Waveforms
3 TA = 25°C
2
1
0
–1 CW WCDMA, UL
WCDMA DL 1C
–2 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
5581fa
1
LT5581
ABSOLUTE MAXIMUM RATINGS
(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
CAUTION: This part is sensitive to electrostatic discharge. It is very important that proper ESD precautions be observed when handling the LT5581.
PIN CONFIGURATION
TOP VIEW
VCC 1
8 CSQ
EN 2 9 7 RFIN
VOUT 3
6 GND
GND 4
5 GND
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
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING
PACKAGE DESCRIPTION
LT5581IDDB#PBF
LT5581IDDB#TRPBF
LDKM
8-Lead (3mm × 2mm) Plastic DFN
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/
TEMPERATURE RANGE –40°C to 85°C
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
fRF = 450MHz 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, 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
Output Variation vs Temperature
Deviation from CW Response; PIN = –34dBm to 0dBm
Normalized to Output at 25˚C, –40°C < TA < 85°C; PIN = –34 to +6dBm
Normalized to Output at 25°C, –40°C < TA < 85°C; PIN = –27 to –10dBm
TETRA π/4 DQPSK CDMA 4-Carrier 64-Channel Fwd 1.23Mcps
±1 dB
±0.5 dB
±0.1 dB ±0.5 dB
5581fa
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
2nd Order Harmonic Distortion 3rd Order Harmonic Distortion fRF = 880MHz RF Input Power Ra.