LT5581 Datasheet by Analog Devices Inc.

Datasheet Feedback/Errors

LTLII‘IEAQ LT5581 TECHNOLOGY L7 LJUW 1

LT5581

5581fb

For more information www.linear.com/LT5581

TYPICAL APPLICATION

DESCRIPTION

6GHz RMS Power Detector

with 40dB Dynamic Range

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 mea-

surement 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 out-

put 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.

10MHz to 6GHz Infrastructure Power

Amplifier Level Control

FEATURES

APPLICATIONS

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

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

Linearity Error vs RF Input Power,

2140MHz Modulated Waveforms

VCC

VOUT

GND

CSQ

RFIN

GNDGND

GND

DIGITAL

POWER

CONTROL

POWER

AMP

DIRECTIONAL

COUPLER

0.01µF

1000pF

0.1µF

VCC

2.7VDC TO 5.25VDC

RFIN RFOUT

CMATCH

LMATCH

68Ω

50Ω

CFILT

0.01µF

5581 TA01a

LT5581

ADC

–2

–1

–3

RF INPUT POWER (dBm)

LINEARITY ERROR (dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 TA01b

TA = 25°C

WCDMA, UL

WCDMA DL 1C

WCDMA DL 4C

LTE DL 1C

LTE DL 4C

L, LT, LT C , LT M, 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.

LT558 1 7 \ DDB PACKAGE MEAD (3mm x 2mm) PLAS'HC DFN

LT5581

5581fb

For more information www.linear.com/LT5581

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.

PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS

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.

(Note 1)

TOP VIEW

DDB PACKAGE

8-LEAD (3mm × 2mm) PLASTIC DFN

1VCC

VOUT

GND

CSQ

RFIN

GND

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 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

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 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

LT558 1 L7 LJUW 3

LT5581

5581fb

For more information www.linear.com/LT5581

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.

ELECTRICAL CHARACTERISTICS

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

fRF = 880MHz

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

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 –34 to 6 dBm

Linear Dynamic Range, CW (Note 3) ±1dB Linearity Error 43 dB

Linear Dynamic Range, WCDMA (Note 3) ±1dB Linearity Error; 4-Carrier WCDMA 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

fRF = 2600MHz

RF Input Power Range Externally Matched to 50Ω Source –34 to 6 dBm

Linear Dynamic Range, CW (Note 3) ±1dB Linearity Error 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

Maximum Deviation from CW Response

PIN = –34 to 2dBm

WiMAX OFDMA Preamble

WiMAX OFDM Burst

±0.1

±0.5

fRF = 3500MHz

RF Input Power Range Externally Matched to 50Ω Source –30 to 6 dBm

Linear Dynamic Range, CW (Note 3) ±1dB Linearity Error 36 dB

Output Slope 31 mV/dB

Logarithmic Intercept (Note 5) –41 dBm

Output Variation vs Temperature Normalized to Output at 25°C, –40°C < TA < 85°C;

PIN = –30 to +6dBm

±1 dB

LT558 1 4 L7LJ1W

LT5581

5581fb

For more information www.linear.com/LT5581

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.

ELECTRICAL CHARACTERISTICS

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

fRF = 5800MHz

RF Input Power Range Externally Matched to 50Ω Source –25 to 6 dBm

Linear Dynamic Range, CW (Note 3) ±1dB Linearity Error 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

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 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) l2 V

EN Input Low Voltage (Off) l0.3 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 l2.7 3.3 5.25 V

Supply Current No RF Input Signal 1.4 mA

Shutdown Current EN = 0.3V, VCC = 3.3V 0.2 6 µA

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.

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.

LT558 1 L7 LJUW 5

LT5581

5581fb

For more information www.linear.com/LT5581

Performance characteristics taken at VCC = 3.3V,

EN = 3.3V and TA = 25°C, unless otherwise noted. (Test circuit shown in Figure 1)

TYPICAL PERFORMANCE CHARACTERISTICS

Output Voltage and Linearity Error

at 450MHz

Linearity Error Temperature

Variation from 25°C at 450MHz

Linearity Error vs RF Input Power,

450MHz Modulated Waveforms

Output Voltage and Linearity Error

at 880MHz

Linearity Error Temperature

Variation from 25°C at 880MHz

Linearity Error vs RF Input Power,

880MHz Modulated Waveforms

Output Voltage vs Frequency Output Voltage vs Frequency Linearity Error vs Frequency

RF INPUT POWER (dBm)

–40

VOUT (V)

0.8

1.8

2.0

–30 –20 –10

0.4

1.4

0.6

1.6

0.2

1.2

1.0

–35 –25 010

–15 –5 5

5581 G01

10MHz

450MHz

880MHz

2.14GHz

2.6GHz

3.5GHz

5.8GHz

TA = 25°C

RF INPUT POWER (dBm)

–40

VOUT (V)

0.8

1.8

2.0

–30 –20 –10

0.4

1.4

0.6

1.6

0.2

1.2

1.0

–35 –25 010

–15 –5 5

5581 G02

880MHz

2.14GHz

2.6GHz

3.5GHz

TA = 25°C

RF INPUT POWER (dBm)

–40

LINEARITY ERROR (dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G03

10MHz

450MHz

880MHz

2.14GHz

2.6GHz

3.5GHz

5.8GHz

TA = 25°C

–2

–1

–3

RF INPUT POWER (dBm)

–40

VOUT (V)

0.8

1.8

2.0

–30 –20 –10

0.4

1.4

0.6

1.6

0.2

1.2

1.0

–0.5

2.0

2.5

–1.5

1.0

–1.0

1.5

–2.0

–2.5

0.5

–35 –25 010

–15 –5 5

5581 G04

25°C

85°C

–40°C

LINEARITY ERROR (dB)

–1

–2

–3

RF INPUT POWER (dBm)

–40

VARIATION (dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G05

–40°C

85°C

–2

–1

–3

RF INPUT POWER (dBm)

LINEARITY ERROR(dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G06

TA = 25°C

TETRA

CDMA 4C

RF INPUT POWER (dBm)

–40

VOUT (V)

LINEARITY ERROR (dB)

0.8

1.8

2.0

–30 –20 –10

0.4

1.4

0.6

1.6

0.2

1.2

1.0

–0.5

2.0

2.5

–1.5

1.0

–1.0

1.5

–2.0

–2.5

0.5

–35 –25 010

–15 –5 5

5581 G07

25°C

85°C

–40°C 2

–2

–1

–3

RF INPUT POWER (dBm)

–40

VARIATION (dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G08

–40°C

85°C

–2

–1

–3

RF INPUT POWER (dBm)

LINEARITY ERROR(dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G09

TA = 25°C

EDGE

LT558 1 p.-/ / \ r"" if K u= \ \navc -\ / \ ”\jillv K ,— L7HUW

LT5581

5581fb

For more information www.linear.com/LT5581

TYPICAL PERFORMANCE CHARACTERISTICS

Output Voltage and Linearity Error

at 2600MHz

Linearity Error Temperature

Variation from 25°C at 2600MHz

Linearity Error vs RF Input Power,

2.6GHz Modulated Waveforms

Output Voltage and Linearity Error

at 3500MHz

Linearity Error Temperature

Variation from 25°C at 3500MHz

Linearity Error vs RF Input Power,

3.5GHz Modulated Waveforms

Output Voltage and Linearity Error

at 2140MHz

Linearity Error Temperature

Variation from 25°C at 2140MHz

Linearity Error vs RF Input Power,

2140MHz Modulated Waveforms

RF INPUT POWER (dBm)

–40

VOUT (V)

LINEARITY ERROR (dB)

0.8

1.8

2.0

–30 –20 –10

0.4

1.4

0.6

1.6

0.2

1.2

1.0

–0.5

2.0

2.5

–1.5

1.0

–1.0

1.5

–2.0

–2.5

0.5

–35 –25 010

–15 –5 5

5581 G10

25°C

85°C

–40°C 2

–2

–1

–3

RF INPUT POWER (dBm)

–40

VARIATION (dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G11

–40°C

85°C

–2

–1

–3

RF INPUT POWER (dBm)

LINEARITY ERROR (dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G12

TA = 25°C

WCDMA, UL

WCDMA DL 1C

WCDMA DL 4C

LTE DL 1C

LTE DL 4C

RF INPUT POWER (dBm)

–40

VOUT (V)

LINEARITY ERROR (dB)

0.8

1.8

2.0

–30 –20 –10

0.4

1.4

0.6

1.6

0.2

1.2

1.0

–0.5

2.0

2.5

–1.5

1.0

–1.0

1.5

–2.0

–2.5

0.5

–35 –25 0

–15 –5 5 10

5581 G13

25°C

85°C

–40°C 2

–2

–1

–3

RF INPUT POWER (dBm)

–40

VARIATION (dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G14

–40°C

85°C

–2

–1

–3

RF INPUT POWER (dBm)

LINEARITY ERROR (dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G15

TA = 25°C

WiMax OFDM PREAMBLE

WiMax OFDM BURST

WiMax OFDMA PREAMBLE

RF INPUT POWER (dBm)

–40

VOUT (V)

LINEARITY ERROR (dB)

0.8

1.8

2.0

0–30 –20 –10 10

0.4

1.4

0.6

1.6

0.2

1.2

1.0

–0.5

2.0

2.5

–1.5

1.0

–1.0

1.5

–2.0

–2.5

0.5

–35 –25 0

–15 –5 5

5581 G16

25°C

85°C

–40°C 2

–2

–1

–3

RF INPUT POWER (dBm)

–40

VARIATION (dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G17

–40°C

85°C

–2

–1

–3

RF INPUT POWER (dBm)

LINEARITY ERROR (dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G18

TA = 25°C

WiMax OFDMA PREAMBLE

WiMax OFDM BURST

LT558 1 L7 LJUW A 5'07 ‘ \ ”\VT: ‘ r"; / ~1pr “' :1,.——~ // ”# ﬂﬂiﬂ H 13,.”~

LT5581

5581fb

For more information www.linear.com/LT5581

TYPICAL PERFORMANCE CHARACTERISTICS

Slope vs Frequency Slope Distribution vs Temperature Supply Current vs Supply Voltage

Logarithmic Intercept

vs Frequency

Logarithmic Intercept Distribution

vs Temperature

Output Voltage and Linearity Error

at 5800MHz

Linearity Error Temperature

Variation from 25°C at 5800MHz

Linearity Error vs RF Input Power,

5.8GHz Modulated Waveforms

RF INPUT POWER (dBm)

–40

VOUT (V)

LINEARITY ERROR (dB)

0.8

1.8

2.0

0–30 –20 –10 10

0.4

1.4

0.6

1.6

0.2

1.2

1.0

–0.5

2.0

2.5

–1.5

1.0

–1.0

1.5

–2.0

–2.5

0.5

–35 –25 0

–15 –5 5

5581 G19

25°C

85°C

–40°C 2

–2

–1

–3

RF INPUT POWER (dBm)

–40

VARIATION (dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G20

–40°C

85°C

–2

–1

–3

RF INPUT POWER (dBm)

LINEARITY ERROR (dB)

–30 –20 –10

–35 –25 010

–15 –5 5

5581 G21

TA = 25°C

WiMax OFDM BURST

FREQUENCY (GHz)

SLOPE (mV/dB)

1 2 43 5

5581 G22

TA = 25°C

SUPPLY VOLTAGE (V)

2.6

SUPPLY CURRENT (mA)

1.6

1.8

1.4

1.2

3.4 4.2

33.8 4.6 5 5.4

1.0

0.8

2.0

5581 G24

–40°C

85°C

25°C

FREQUENCY (GHz)

–50

LOGARITHMIC INTERCEPT (dBm)

–40

1 2 43 5

–30

–45

–35

5581 G25

TA = 25°C

SLOPE (mV/dB)

DISTRIBUTION (%)

029 30 31 32 33 34

5581 G23

TA = 85°C

TA = 25°C

TA = –40°C

LOGARITHMIC INTERCEPT (dBm)

–48

DISTRIBUTION (%)

0–47 –46 –45 –44 –43 –41–42

5581 G26

TA = 85°C

TA = 25°C

TA = –40°C

LT558 1 w W PW =4DdBm ‘ = 72m w P =IDdBm FWD m w P‘ Em P‘ Vauaam L7 LINE/“2 v toerch

LT5581

5581fb

For more information www.linear.com/LT5581

TYPICAL PERFORMANCE CHARACTERISTICS

Output Transient Response

Output Transient Response with

CW RF and EN Pulse

Output Voltage and Linearity Error

vs VCC at 2140MHz

Return Loss vs Frequency

Reference in Figure 1 Test Circuit

Output Transient Response with

RF and EN Pulse

RF INPUT POWER (dBm)

–40

VOUT (V)

LINEARITY ERROR (dB)

0.8

1.8

2.0

–30 –20 –10

0.4

1.4

0.6

1.6

0.2

1.2

1.0

–0.5

2.0

2.5

–1.5

1.0

–1.0

1.5

–2.0

–2.5

0.5

–35 –25 010

–15 –5 5

5581 G28

3.3V

TA = 25°C

FREQUENCY (GHz)

–30

RETURN LOSS (dB)

–25

–20

–15

–10

12 3 4

5581 G29

5 6

–5

L1, C1 = 2.2nH, 1.5pF

L1, C1 = 1nH, 1.5pF

L1, C1 = 0nH, 1pF

L1, C1 = 0nH, 0.5pF

L1, C1 = 0nH, 0pF

TA = 25°C

TIME (ms)

OUTPUT VOLTAGE (V)

RF PULSE ENABLE (V)

1.5

2.0

2.5

0.7

1.0

0.5

0.2 0.4

0.1 0.9

0.3 0.5 0.8

0.6 1

–0.5

3.0

–5

–10

–15

–20

–25

5581 G30

RF & EN PULSE ON

RF & EN

PULSE

OFF

RF & EN

PULSE

OFF

PIN = 10dBm

PIN = 0dBm

PIN = –10dBm

PIN = –20dBm

PIN = –30dBm

TA = 25°C, VCC = 5V

TIME (µs)

OUTPUT VOLTAGE (V)

RF PULSE ENABLE (V)

1.5

2.0

2.5

1.0

0.5

20 40

10 90

30 50 80

60 100

3.0

–5

–10

–15

–20

5581 G31

RF PULSE ON

PULSE

OFF

PULSE

OFF

PIN = 10dBm

PIN = 0dBm

PIN = –10dBm

PIN = –20dBm

PIN = –30dBm

TA = 25°C, VCC = 5V

TIME (ms)

OUTPUT VOLTAGE (V)

ENABLE (V)

1.5

2.0

2.5

0.7

1.0

0.5

0.2 0.4

0.1 0.9

0.3 0.5 0.8

0.6 1

–0.5

3.0

–2

–4

–6

–8

–10

5581 G32

EN PULSE ON

PULSE

OFF

PULSE

OFF

PIN = 10dBm

PIN = 0dBm

PIN = –10dBm

PIN = –20dBm

PIN = –30dBm

TA = 25°C

Supply Current vs RF Input Power

RF INPUT POWER (dBm)

–25

SUPPLY CURRENT (mA)

–20 –15 –10 –5 50 10

5581 G27

TA = 25°C

LT558 1 E [1 E I w '1 TH Fara my L7 LJUW 9

LT5581

5581fb

For more information www.linear.com/LT5581

PIN FUNCTIONS

VCC (Pin 1): Power Supply, 2.7V to 5.25V. VCC

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.

RFIN (Pin 7): RF Input. Should be DC-blocked with coupling

capacitor; 1000pF recommended. This pin has an internal

200Ω termination.

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.

BLOCK DIAGRAM

LT5581

EXPOSED

PAD

OUTPUT

BUFFER

VOUT

RFIN

5581 BD

EN VCC

CSQ

8 1 4 5 6

150kHz LPF 300Ω

GND

RMS

DETECTOR

BIAS

LT558 1 || || C6 000 || __ II as C3? .1.” — — I ' T I _ _ ' + 17: ;: ‘IO

LT5581

5581fb

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TEST CIRCUIT

Figure 1. Evaluation Circuit Schematic

REF DES VALUE SIZE PART NUMBER

C6 100pF 0603 AVX 06033A101KAT2A

C7 0.1µF 0603 AVX 06033C104KAT2A

C3 0.01µF 0603 AVX 06033C103KAT2A

C2 1000pF 0603 AVX 06033C102KAT2A

R2 68Ω 0603

FREQUENCY

RANGE

RFIN MATCH

L1 C1

1GHz to 2.2GHz 2.2nH 1.5pF

2GHz to 2.6GHz 1.2nH 1.5pF

2.6GHz to 3.4GHz 0 1pF

3.8GHz to 5.5GHz 0 0.5pF

4.6GHz to 6GHz 0 0

VCC

NC NC

VOUT

GND

CSQ

RFIN

GNDGND

GND

2.2nH

0.01µF

PINS 4, 5, 6: OPTIONAL GROUND

1000pF

VCC

68Ω

0Ω

OPT

5581 F01

LT5581

OPT

GND

EE = 4.4

0.018"

0.062"

VOUT

RFIN

0.1µF

100pF

1.5pF

' cm LT5581IDDB :.nrmnmmr.: . . .HW.”W. . .. L7 HEW LT558 1 ‘I‘I

LT5581

5581fb

For more information www.linear.com/LT5581

APPLICATIONS INFORMATION

OPERATION

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 import-

ant to place many ground vias directly under the package.

RF Input Matching

The input resistance is about 205Ω. Input capacitance

is 1.6pF. The impedance vs frequency of the RF input is

detailed in Table 1.

Figure 2. Top Side of Evaluation Board Figure 3. Bottom Side of Evaluation Board

Table 1. RF Input Impedance

FREQUENCY

(MHz)

INPUT

IMPEDANCE

(Ω)

S11

MAG ANGLE (°)

10 203.6-j5.5 0.606 –0.8

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

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 F035581 F02

LT558 1

LT5581

5581fb

For more information www.linear.com/LT5581

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

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

APPLICATIONS INFORMATION

Figure 4. Simplified Circuit Schematic of the RF Input Interface Figure 5. Input Reflection Coefficient

CSQ

VCC

5581 F04

205Ω

LT5581

0.01µF

1000pF

68Ω

RFIN

(MATCHED)

20pF

RFIN

211 L7 LJUW LT558 1 13

LT5581

5581fb

For more information www.linear.com/LT5581

APPLICATIONS INFORMATION

the output pin, to form an RC lowpass filter. The internal

300Ω resistor in series with the output pin enables filter-

ing 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:

fC=

2πCLOAD(300+RSS )

Figure 8 shows the transient response for a 2.6GHz Wi-

MAX signal, with preamble and burst ripple reduced by a

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 QPSK3/4.

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 6. Simplified Circuit Schematic of the Output Interface

Figure 8. Residual Ripple for 2.6GHz WiMAX OFDM 802.16-2004

Figure 7. Residual Ripple, Output Transient Response

for RF Pulse with WCDMA 4-Carrier Modulation

Figure 9. Residual Ripple, Output Transient Times for RF Pulse

with WCDMA 4-Carrier Modulation vs External Filter Capacitor C4

300Ω RSS

VOUT

INPUT

VCC

40µA

VOUT

(FILTERED)

CLOAD

5581 F06

LT5581

TIME (µs)

OUTPUT VOLTAGE (V)

0.8

1.0

1.2

0.6

0.4

0 70

20 40

10 90

30 50 80

60 100

0.2

1.4

1.10

1.15

1.20

1.05

1.00

0.95

0.90

1.25

5581 F07

TA = 25°C

NO CAP

0.01µF

TIME (ms)

OUTPUT VOLTAGE (V)

0.8

1.0

1.2

0.6

0.4

0 1.4

0.4 0.8

0.2 1.8

0.6 1 1.6

1.2 2

0.2

1.4

5581 F08

TA = 25°C NO CAP

0.047µF

EXTERNAL CAPACITOR (µF)

0.001

OUTPUT RIPPLE PEAK-TO-PEAK (dB)

RISE TIME AND FALL TIME (µs)

0.01 0.1 1

100

1000

5581 F09

TA = 25°C

RIPPLE

RISE

FALL

LT558 1 R‘SE TIM MHz 14 L7LJCUEN2

LT5581

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For more information www.linear.com/LT5581

Figure 10. RF Pulse Response Rise Time

and Fall Time vs RF Input Power

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 sta-

tistics 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

resulting deviation in the output voltage of the detector

shows the effect of the internal 150kHz filter.

APPLICATIONS INFORMATION

Figure 11. Output DC Voltage Deviation and Residual

Ripple vs 2-Tone Separation Frequency

Figure 12. Output Voltage Noise Density Figure 13. Integrated Output Voltage Noise

1 Steve Murray, “Beware of Spectrum Analyzer Power Averaging Techniques,” Microwaves

& RF, Dec. 2006.

INPUT POWER (dBm)

–30

RISE TIME AND FALL TIME (µs)

–20 –10

–25 –15 –5 0 5

5581 F10

FALL TIME

RISE TIME

= 25°C

2-TONE FREQUENCY SEPARATION (MHz)

0.001

OUTPUT AC RIPPLE (dB)

DEVIATION OF OUTPUT VOLTAGE (dB)

0.01 0.1 110

–1.5

–1.0

–0.5

–2.0

–2.5

–3.0

5581 F11

TA = 25°C

FREQUENCY (kHz)

0.1

NOISE VOLTAGE (µVRMS/ Hz)

2.0

4.0

1.0

3.5

1.5

0.5

3.0

2.5

1100 1000

5581 F12

0dBm

–10dBm

–20dBm

–30dBm

NO RF INPUT

TA = 25°C

FREQUENCY (kHz)

0.1

INTEGRATED NOISE (mVRMS)

0.8

1.8

2.0

0.4

1.4

0.6

1.6

0.2

1.2

1.0

1100 1000

5581 F13

0dBm

–10dBm

–20dBm

–30dBm

NO RF INPUT

TA = 25°C

L7 LJUW LT558 1 15

LT5581

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For more information www.linear.com/LT5581

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.

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.

APPLICATIONS INFORMATION

Figure 14. Enable Pin Simplified Schematic

VCC

5581 F14

300k 300k

LT5581

500k

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.

LT558 1 ‘ x 1 + {:ﬁﬁﬂjﬁ: J i 3334; Lllﬁlgﬂjf‘e : k 4‘ 7‘ i T LAU 1U Us? \_ $ V’lﬂ \mﬂ‘ \ 1 Egg; D a F +

LT5581

5581fb

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PACKAGE DESCRIPTION

2.00 ±0.10

(2 SIDES)

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

0.40 ±0.10

BOTTOM VIEW—EXPOSED PAD

0.56 ±0.05

(2 SIDES)

0.75 ±0.05

R = 0.115

TYP

R = 0.05

TYP

2.15 ±0.05

(2 SIDES)

3.00 ±0.10

(2 SIDES)

PIN 1 BAR

TOP MARK

(SEE NOTE 6)

0.200 REF

0 – 0.05

(DDB8) DFN 0905 REV B

0.25 ±0.05

0.50 BSC

PIN 1

R = 0.20 OR

0.25 × 45°

CHAMFER

0.25 ±0.05

2.20 ±0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

0.61 ±0.05

(2 SIDES)

1.15 ±0.05

0.70 ±0.05

2.55 ±0.05

PACKAGE

OUTLINE

0.50 BSC

DDB Package

8-Lead Plastic DFN (3mm × 2mm)

(Reference LTC DWG # 05-08-1702 Rev B)

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

LT558 1 L7 LJUW 17

LT5581

5581fb

For more information www.linear.com/LT5581

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.

REVISION HISTORY

REV DATE DESCRIPTION PAGE NUMBER

A 4/10 Updated Note 2 in Electrical Characteristics Section 4

B 8/15 Changed Enable Pin input voltage to 2V 15

LT558 1

LT5581

5581fb

For more information www.linear.com/LT5581

 LINEAR TECHNOLOGY CORPORATION 2008

LT 0815 REV B • PRINTED IN USA

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com/LT5581

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