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FEATURES
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LT5570 Fast Responding, 40MHz to 2.7GHz Mean-Squared Power Detector DESCRIPTION
The LT(R)5570 is a 40MHz to 2.7GHz monolithic Logarithmic Mean-Squared RF power detector. It is capable of RMS measurement of an AC signal with wide dynamic range, from -52dBm to 13dBm depending on frequency. The power of the AC signal in an equivalent decibel-scaled value is precisely converted into DC voltage on a linear scale, independent of the crest factor of the waveforms. The LT5570 is suitable for precision RF power measurement and level control for a wide variety of RF standards, including CDMA, W-CDMA, CDMA2000, TD-SCDMA and WiMAX. The DC output is buffered with a low output impedance amplifier capable of driving a high capacitance load.
, 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 7262661, 7259620, 7268608.
Frequency Range: 40MHz to 2.7GHz Accurate RMS Power Measurement of High Crest Factor Modulated Waveforms Linear DC Output vs Input Power in dBm Linear Dynamic Range: Up to 60dB Exceptional Accuracy over Temperature: 0.3dB Fast Response Time: 0.5s Rise Time, 8s Fall Time Low Supply Current: 26.5mA Low Impedance Output Buffer Capable of Driving High Capacitance Load Small 3mm x 3mm 10-Lead DFN Package
APPLICATIONS
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RMS Power Measurement RF Power Control Receive and Transmit Gain Control W-CDMA, CDMA2000, TD-SCDMA, WiMAX RF Instrumentation
TYPICAL APPLICATION
40MHz to 2.7GHz Mean-Squared Power Detector
5V 1F RF INPUT 1:4 NC 1nF 1 2 3 4 5 10 9 8 7 6 VOUT ENABLE VOUT (V) 22nF
Output Voltage, Linearity Error vs Input Power, 25C (2140 MHz)
2.4 2.0 1.6 1.2 0.8 0.4 0 -45 CW 4CH WCDMA 3CH CDMA2000 -35 -15 5 -25 -5 RF INPUT POWER (dBm) 15 3 2 LINEARITY ERROR (dB) 1 0 -1 -2 -3
VCC IN+ DEC IN- GND LT5570
FLTR EN DNC DNC OUT
5570 TA01a
5570 TA01b
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LT5570 ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
TOP VIEW VCC IN+ DEC IN- GND 1 2 3 4 5 10 FLTR 9 EN 8 DNC 7 DNC 6 OUT
Supply Voltage .........................................................5.5V Enable Voltage .................................-0.3V to VCC + 0.3V Input Signal Power (Differential) ..........................15dBm TJMAX .................................................................... 125C Operating Temperature Range.................. -40C to 85C Storage Temperature Range................... -65C to 125C CAUTION: This part is sensitive to electrostatic discharge. It is very important that proper ESD precautions be observed when handling the LT5570.
DD PACKAGE 10-LEAD (3mm 3mm) PLASTIC DFN TJMAX = 125C, JA = 43C/W EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH LT5570IDD#PBF TAPE AND REEL LT5570IDD#TRPBF PART MARKING LCJQ PACKAGE DESCRIPTION 10-Lead (3mm x 3mm) Plastic DFN TEMPERATURE RANGE -40C to 85C 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/
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C, VCC = 5V, EN = 5V, unless otherwise noted. Test circuits are shown in Figures 1 and 3. (Notes 2 and 3).
PARAMETER AC Input Input Frequency Range (Note 4) Input Impedance fRF = 500MHz RF Input Power Range Linear Dynamic Range (Note 5) Output Slope Logarithmic Intercept Output Variation vs Temperature Deviation from CW Response 2nd Order Harmonic Distortion 3rd Order Harmonic Distortion Normalized to Output at 25C -40C < TA < 85C; PIN = -50dBm to 13dBm 11dB Peak to Average Ratio (3-Carrier CDMA2K) 12dB Peak to Average Ratio (4-Carrier WCDMA) At RF Input; CW Input; PIN = 10dBm At RF Input; CW Input; PIN = 10dBm CW Input; 1:4 Balun Matched into 50 Source 1dB Linearity Error, TA = -40C to 85C -52 to 13 62 36.9 -54.8 0.5 0.4 0.3 61 66 dBm dB mV/dB dBm dB dB dB dBc dBc
l
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP 40 to 2700 200/1
MAX
UNITS MHz /pF
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LT5570 ELECTRICAL CHARACTERISTICS
PARAMETER fRF = 880MHz RF Input Power Range Linear Dynamic Range (Note 5) Output Slope Logarithmic Intercept Output Variation vs Temperature Deviation from CW Response 2nd Order Harmonic Distortion 3rd Order Harmonic Distortion fRF = 2140MHz RF Input Power Range Linear Dynamic Range (Note 5) Output Slope Logarithmic Intercept Output Variation vs Temperature Deviation from CW Response fRF = 2700MHz RF Input Power Range Linear Dynamic Range (Note 5) Output Slope Logarithmic Intercept Output Variation vs Temperature Deviation from CW Response Output Output DC Voltage Output Impedance Sourcing/Sinking Rise Time Fall Time 0.2V to 1.6V, 10% to 90%, C1 = 22nF fRF = 2140MHz , 1.6V to 0.2V, 90% to 10%, C1 = 22nF fRF = 2140MHz , No RF Signal Present 0.1 100 5/2.5 0.5 8 V mA S S Normalized to Output at 25C -40C < TA < 85C; PIN = -31dBm to 13dBm 11dB Peak to Average Ratio (3-Carrier CDMA2K) 12dB Peak to Average Ratio (4-Carrier WCDMA) CW Input; 1:4 Balun Matched into 50 Source 1dB Linearity Error, TA = -40C to 85C -35 to 13 48 36.4 -38.5 0.2 0.1 0.5 dBm dB mV/dB dBm dB dB Normalized to Output at 25C -40C < TA < 85C; PIN = -36dBm to 13dBm 11dB Peak to Average Ratio (3-Carrier CDMA2K) 12dB Peak to Average Ratio (4-Carrier WCDMA) CW Input; 1:4 Balun Matched into 50 Source 1dB Linearity Error, TA = -40C to 85C 47 34.8 -43.6 -38 to 13 51 36.5 -40.6 0.3 0.1 0.2 39.0 -37.6 dBm dB mV/dB dBm dB dB dB Normalized to Output at 25C -40C < TA < 85C; PIN = -47dBm to 13dBm 11dB Peak to Average Ratio (3-Carrier CDMA2K) 12dB Peak to Average Ratio (4-Carrier WCDMA) At RF Input; CW Input; PIN = 10dBm At RF Input; CW Input; PIN = 10dBm CW Input; 1:4 Balun Matched into 50 Source 1dB Linearity Error, TA = -40C to 85C -48 to 13 61 37.7 -51.9 0.4 0.3 0.2 60 61 dBm dB mV/dB dBm dB dB dBc dBc CONDITIONS
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C, VCC = 5V, EN = 5V, unless otherwise noted. Test circuits are shown in Figures 1 and 3. (Notes 2 and 3).
MIN TYP MAX UNITS
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LT5570 ELECTRICAL CHARACTERISTICS
PARAMETER Enable (EN) Low = Off, High = On EN Input High Voltage (On) EN Input Low Voltage (Off) Enable Pin Input Current Turn ON Time Turn OFF Time Power Supply Supply Voltage Supply Current Shutdown Current EN = 0V, VCC = 5V
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The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C, VCC = 5V, EN = 5V, unless otherwise noted. Test circuits are shown in Figures 1 and 3. (Notes 2 and 3).
CONDITIONS MIN 2 1 68 1 5 4.75 5 26.5 0.1 5.25 32.5 100 TYP MAX UNITS V V A s s V mA A
EN = 5V VOUT within 10% of Final Value, C1 = 22nF VOUT < 0.1V, C1 = 22nF
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: Specifications over the -40C to +85C temperature range are assured by design, characterization and correlation with statistical process controls.
Note 3: A 1:4 input transformer is used for the input matching to 50 source. Note 4: Operation over a wider frequency range is possible with reduced performance. Consult the factory for information and assistance. Note 5: The linearity error is calculated by the difference between the incremental slope of the output and the average output slope from -30dBm to 2dBm. The dynamic range is defined as the range over which the linearity error is within 1dB.
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LT5570 TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage vs Frequency
2.4 2.0 1.6 VOUT (V) 1.2 0.8 0.4 0 -55 -45 500MHz 880MHz 2140MHz 2700MHz -35 -25 -15 -5 RF INPUT POWER (dBm) 5 15 LINEARITY ERROR (dB) TA = 25C 3 2 1 0 -1 -2 -3 -55 -45 500MHz 880MHz 2140MHz 2700MHz -35 -25 -15 -5 RF INPUT POWER (dBm) 5 15
(Test Circuits Shown in Figures 1 and 3)
Linearity Error vs Frequency
TA = 25C
5570 G01
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Output Voltage, Linearity Error vs RF Input Power, 500MHz
2.4 2.0 1.6 VOUT (V) 1.2 0.8 0.4 0 -55 -45 TA = -40C TA = 25C TA = 85C -35 -25 -15 -5 RF INPUT POWER (dBm) 5 15 3 2 LINEARITY ERROR (dB) LINEARITY ERROR (dB) 1 0 -1 -2 -3 3 2 1 0 -1 -2
Linearity Error vs RF Input Power, 500MHz Modulated Waveforms
TA = 25C
-3 -55 -45
CW 4CH WCDMA 3CH CDMA2000 -35 -25 -15 -5 RF INPUT POWER (dBm) 5 15
5570 G03
5570 G04
Output Voltage, Linearity Error vs RF Input Power, 880MHz
2.4 2.0 1.6 VOUT (V) 1.2 0.8 0.4 0 -55 -45 TA = -40C TA = 25C TA = 85C -35 -25 -15 -5 RF INPUT POWER (dBm) 5 15 3 2 1 0 -1 -2 -3 LINEARITY ERROR (dB) LINEARITY ERROR (dB) 3 2 1 0 -1 -2
Linearity Error vs RF Input Power, 880MHz Modulated Waveforms
TA = 25C
-3 -55 -45
CW 4CH WCDMA 3CH CDMA2000 -5 -35 -25 -15 RF INPUT POWER (dBm) 5 15
5570 G05
5570 G06
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LT5570 TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage, Linearity Error vs RF Input Power, 2140MHz
2.4 2.0 1.6 VOUT (V) 1.2 0.8 0.4 0 -45 TA = -40C TA = 25C TA = 85C -35 -15 5 -25 -5 RF INPUT POWER (dBm) 15
5570 G07
(Test Circuits Shown in Figures 1 and 3) Linearity Error vs RF Input Power, 2140MHz Modulated Waveforms
3 2 LINEARITY ERROR (dB) LINEARITY ERROR (dB) 1 0 -1 -2 -3
3 2 1 0 -1 -2 -3 -45
TA = 25C
CW 4CH WCDMA 3CH CDMA2000 -35 -15 5 -25 -5 RF INPUT POWER (dBm) 15
5570 G08
Output Voltage, Linearity Error vs RF Input Power, 2700MHz
2.4 2.0 1.6 VOUT (V) 1.2 0.8 0.4 0 -45 TA = -40C TA = 25C TA = 85C -35 -15 5 -25 -5 RF INPUT POWER (dBm) 15
5570 G09
Linearity Error vs RF Input Power, 2700MHz Modulated Waveforms
3 2 1 0 -1 -2 -3 LINEARITY ERROR (dB) LINEARITY ERROR (dB) 3 2 1 0 -1 -2 -3 -45 CW 4CH WCDMA 3CH CDMA2000 -35 -15 5 -25 -5 RF INPUT POWER (dBm) 15
5570 G10
TA = 25C
Slope vs Frequency
42 TA = 25C LOGARITHMIC INTERCEPT (dBm) -35
Logarithmic Intercept vs Frequency
TA = 25C
40 SLOPE (mV/dB)
-40
38
-45
36
-50
34
-55
32
-60 0 500 1000 1500 2000 FREQUENCY (MHz) 2500 3000
0
500
1000 1500 2000 FREQUENCY (MHz)
2500
3000
5570 G11
5570 G12
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LT5570 TYPICAL PERFORMANCE CHARACTERISTICS
Output Transient Response, C1 = 22nF
3.0 2.5 2.0 VOUT (V) 1.5 1.0 0.5 0 0 5 10 15 20 25 30 35 40 45 50 TIME (s)
5570 G13
(Test Circuits Shown in Figures 1 and 3)
Output Transient Response, C1 = 1F
6 3.0 2.5 RF PULSE ENABLE (V) 2.0 VOUT (V) 1.5 1.0 0.5 0 0 100 200 300 400 500 600 700 800 900 1000 TIME (s)
5570 G14
6 RF PULSE OFF RF PULSE ON RF PULSE OFF 2 RF PULSE ENABLE (V) -2 -6 -10 -14 -18
RF PULSE OFF
RF PULSE ON
RF PULSE OFF
2 -2 -6 -10 -14 -18
AT 2140MHz PIN = 10dBm PIN = 0dBm PIN = -10dBm PIN = -20dBm PIN = -30dBm
AT 2140MHz PIN = 10dBm PIN = 0dBm PIN = -10dBm PIN = -20dBm PIN = -30dBm
Slope Distribution vs Temperature
45 40 PERCENTAGE DISTRIBUTION (%) 35 30 25 20 15 10 5 0 35.4 36 36.6 37.2 37.8 38.4 SLOPE (mV/dB) 39
5570 G15
Logarithmic Intercept Distribution vs Temperature
45 40 PERCENTAGE DISTRIBUTION (%) 35 30 25 20 15 10 5 0 -44 -43 -42 -41 -40 -39 LOGARITHMIC INTERCEPT (dBm) -38
5570 G16
Supply Current vs Supply Voltage
40 35 SUPPLY CURRENT (mA) 30 25 20 15 10 4.50 TA = -40C TA = 25C TA = 85C 4.75 5.00 5.25 SUPPLY VOLTAGE (V) 5.50
5570 G17
TA = -40 C TA = 25 C TA = 85 C
TA = -40 C TA = 25 C TA = 85 C
Supply Current vs RF Input Power
29 28 SUPPLY CURRENT (mA) RETURN LOSS (dB) 27 26 25 24 23 -55 -45 TA = 25C 0 -5 -10 -15 -20 -25 -30
Input Return Loss vs Frequency Reference in Figure 3
0 -5 RETURN LOSS (dB) -10 -15 -20 -25
Input Return Loss vs Frequency Reference in Figure 1
-35 -25 -15 -5 RF INPUT POWER (dBm)
5
15
0 100 200 300 400 500 600 700 800 900 1000 FREQUENCY (MHz)
5570 G19
-30 500
880MHz 2140MHz 2700MHz 1000 1500 2000 2500 FREQUENCY (MHz) 3000
5570 G20
5570 G18
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LT5570 PIN FUNCTIONS
VCC (Pin 1): Power Supply Pin for the Bias Circuits. Typical current consumption is 26.5mA. This pin should be externally bypassed with 1nF and 1F chip capacitors. IN+, IN- (Pins 2, 4): Differential Input Signal Pins. These pins are preferably driven with a differential signal for optimum performance. The pins are internally biased to VCC - 1.224V and should be DC blocked externally. The differential impedance is about 200. DEC (Pin 3): Input Common Mode Decoupling Pin. This pin is internally biased to VCC - 1.224V. The input impedance is about 1.75K in parallel with a 10pF internal shunt capacitor to ground. The impedance between DEC and IN+ (or IN-) is about 100. The pin can be connected to the center tap of an external balun. An ac-decoupling capacitor may be connected to ground to maintain the IC performance if necessary. GND (Pin 5, Exposed Pad): Circuit Ground Return for the Entire IC. This must be soldered to the printed circuit board ground plane. OUT (Pin 6): DC Output Pin. The output impedance is mainly determined by an internal 100 series resistance that provides output circuit protection if the output is shorted to ground. DNC (Pins 7, 8): Do Not Connect. Don't connect any external component at these pins. Avoid a long wire or metal trace on the PCB. EN (Pin 9): Enable Pin. An applied voltage above 2V will activate the bias for the IC. For an applied voltage below 1V, the circuits will be shut down (disabled) with a corresponding reduction in power supply current. If the enable function is not required, then this pin should be connected to VCC. Typical enable pin input current is 68A for EN = 5V. Note that at no time should the Enable pin voltage be allowed to exceed VCC by more than 0.3V. FLTR (Pin 10): Connection for an External Filtering Capacitor C1. A minimum 22nF capacitor is required for stable ac average power measurement. This capacitor should be connected between Pin 10 and VCC.
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LT5570 TEST CIRCUITS
C1 22nF RF INPUT J1 T1 L1 C7 5 1 1:4 3 2 4 C4 1nF 1 2 3 4 5 VCC IN+ DEC IN- GND EXPOSED PAD LT5570 FLTR EN DNC DNC OUT
5570 F01
C2 1nF
5V C3 1F
10 9 8 7 6 NC NC OUT C6 (OPT) ENABLE R1 100k
REF DES C2, C4 C1 C3 R1
VALUE 1nF 22nF 1F 100k
SIZE 0402 0402 0603 0402
PART NUMBER AVX 0402ZC102KAT AVX 0402YC223KAT Taiyo Yuden LMK107BJ105MA CRCW0402100KFKED T1 L1 8.2nH 3.3nH 1.2nH L1 P/N TOKO LL1005-FH8N25 TOKO LL1005-FH3N35 TOKO LL1005-FH1N25 C7 2.7pF 0.5pF 1pF MURATA GRM1555C1H2R7DZ01 MURATA GRM1555C1HR50CZ01 MURATA GRM1555C1H1R0DZ01
FREQUENCY 880MHz 2140MHz 2700MHz
MURATA LDB21869M20C-001 MURATA LDB212G1020-001 MURATA LDB212G4020-001
Figure 1. Test Schematic for 880MHz, 2140MHz and 2700MHz Applications
Figure 2. Top Side of Evaluation Board for 880MHz, 2140MHz and 2700MHz Applications
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LT5570 TEST CIRCUITS
C1 22nF RF INPUT J1 C7 1nF T2 ETC4-1-2 4 C8 OPT 5 1:4 3 2 1 C4 1nF 1 2 3 4 5 VCC IN+ DEC IN- GND EXPOSED PAD LT5570 FLTR EN DNC DNC OUT
5570 F03
C2 1nF
5V C3 1F
10 9 8 7 6 OUT C6 (OPT) NC NC ENABLE R1 100k
L1 0 C9 0
REF DES C2, C4, C7 C1 C3
VALUE 1nF 22nF 1F
SIZE 0402 0402 0603
PART NUMBER AVX 0402ZCI02KAT AVX 0402YC223KAT Taiyo Yuden LMK107BJ105MA
REF DES R1 T2 C8 C9, L1
VALUE 100k 1:4 OPT 0
SIZE 0402 0402 0402 ETC4-1-2
PART NUMBER CRCW0402100KFKED
CJ05-000M
Figure 3. Test Schematic for 40MHz to 860MHz Applications
Figure 4. Top Side of Evaluation Board for 40MHz to 860MHz Applications
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LT5570 APPLICATIONS INFORMATION
The LT5570 is a mean-squared RF power detector, capable of measuring an RF signal over the frequency range from 40MHz to 2.7GHz, independent of input waveforms with different crest factors such as CW, CDMA, WCDMA, TDSCDMA and WiMAX signals. A wide dynamic range is achieved with very stable output within the full temperature range from -40C to 85C. RF Inputs The differential RF inputs are internally biased at VCC - 1.224V. The differential impedance is about 200. These pins should be DC blocked when connected to ground or other matching components. The impedance vs. frequency of the differential RF input is detailed in the following table.
Table 1. RF Differential Input Impedance
FREQUENCY (MHz) 40 100 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 DIFFERENTIAL INPUT IMPEDANCE () 204 -j 0.6 204 -j 1.8 204 -j 3.6 203.5 -j 7.3 202.8 -j 10.9 201.8 -j 14.5 200.6 -j17.9 199.1 -j21.3 197.3 -j24.7 195.4 -j27.9 193.2 -j31.1 190.8 -j34.2 188.2 -j37.4 185.3 -j40.4 181.9 -j43.5 178.3 -j46.4 174.4 -j49.3 S11 MAG 0.606 0.606 0.606 0.606 0.605 0.604 0.603 0.602 0.601 0.599 0.598 0.596 0.593 0.591 0.589 0.586 0.582 ANGLE () -0.1 -0.3 -0.5 -1.1 -1.6 -2.1 -2.7 -3.2 -3.8 -4.4 -5.0 -5.6 -6.2 -6.9 -7.6 -8.4 -9.2
1nF RF INPUT 100
5570 F05
The LT5570's differential inputs are optimally driven from a fully balanced source. When the signal is from a singleended 50 source, conversion to a differential signal is required to achieve the maximum dynamic range. This is best achieved using a 1:4 balun to match the internal 200 input impedance as shown in Figures 1 and 3. This impedance transformation results in 6dB voltage gain. At high frequency, additional LC elements may be needed for input impedance matching due to the parasitics of the transformer and PCB trace. The approximate RF input power range of the LT5570 is 60dB at frequencies up to 900MHz, even with high crest factor signals such as a 4-carrier W-CDMA waveform. However the minimum detectable RF power level degrades as the input RF frequency increases. Due to the high RF input impedance of the LT5570, a narrow band L-C matching network can be used for the conversion of a single-ended to balanced signal as well. By this means, the sensitivity and overall linear dynamic range of the detector remain the same, without using an RF balun. The LT5570 can also be driven in a single-ended configuration. Figure 5 shows the simplified circuit of this single-ended configuration. The DEC Pin is preferably accoupled to ground via a capacitor rather than left floating.
LT5570 IN+ 1nF DEC IN- 100 100
Figure 5. Single-Ended Input Configuration
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LT5570 APPLICATIONS INFORMATION
2.4 2.0 RESIDUAL RIPPLE (mVRMS) 1.6 VOUT (V) 1.2 0.8 0.4 0.0 -50 500MHz 880MHz 2140MHz 2700MHz -40 0 -30 -20 -10 INPUT POWER (dBm) 10
5570 F06
40 35 30 25 20 15 10 5 0 0
AT 2140MHZ, PIN = 10dBm
320 280 RISE AND FALL TIMES (s) 240 200 160 120 80
RESIDUAL RIPPLE RISE TIME FALL TIME 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 EXTERNAL FILTERING CAPACITOR C1 (F)
5570 F07
40 0
Figure 6. Output Voltage and Linearity Error vs RF Input Power in Single-ended Input Configuration
Figure 7. Residual Ripple, Output Transient Times vs. Filtering Capacitor C1
The DEC pin can be tied to the IN+ (or IN-) Pin directly and ac-coupled to ground while the RF signal is applied to the IN- (or IN+) Pin. By simply terminating the signal side of the inputs with a 100 resistor to ground in front of the ac-blocking capacitor and coupling the other side to ground using a 1nF capacitor, a broadband 50 input match can be achieved with typical input return loss better than 12dB from 40MHz to 2.7GHz. Since there is no voltage conversion gain from impedance transformation in this case, the sensitivity of the detector is reduced by 6dB. The linear dynamic range is reduced by the same amount correspondingly as shown in Figure 6. External Filtering (FLTR) Capacitor C1 This pin is internally biased at VCC - 0.13V via a 2k resistor from voltage supply VCC. To assure stable operation of the LT5570, an external capacitor C1 with a value of 22nF or higher is required to connect the FLTR Pin to VCC. Don't connect this filtering capacitor to ground or any other low voltage reference at any time to avoid an abnormal start-up condition.
C1's value has a dominant effect on the output transient response. The lower the capacitance, the faster the output rise and fall times as illustrated in Figure 7. For signals with AM content such as W-CDMA, ripple can be observed when the loop bandwidth set by C1 is close to the modulation bandwidth of the signal. A 4-carrier W-CDMA RF signal is used as an example in this case. The trade-offs of residual ripple vs. output transient time are also as shown in Figure 7. In general, the LT5570 output ripple remains relatively constant regardless of the RF input power level for a fixed C1 and modulation format of the RF signal. Typically, C1 must be selected to average out the ripple to achieve the desired accuracy of RF power measurement. For a two-tone RF signal with equal power applied to the LT5570 input, Figure 8 shows the variation of the output dc voltage and its RMS value of the residual ac voltage as a function of the delta frequency. Both values are referred to dB by normalizing them to the output slope (about 37mV/dB). In this measurement, C1 = 22nF. Increasing C1 will shift both curves toward a lower frequency.
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LT5570 APPLICATIONS INFORMATION
8 7 DC VOLTAGE VARIATION OUTPUT AC RIPPLE (dB) 6 5 4 3 OUTPUT AC RIPPLE 2 1 0 0.01 0.1 1 AM MODULATION FREQUENCY (MHz) 10 -3 -2 -1 0 C1 = 22nF 1 DEVIATION OF DC OUTPUT VOLTAGE (dB) LT5570 VCC 50A
100 INPUT
OUT
RSS VOUT CLOAD
5570 F08
3566 F09
Figure 8. Output DC Voltage Variation and Residual Ripple vs AM Modulation Frequency
Figure 9. Simplified Circuit Schematic of the Output Interface
The high performance RF circuits inside the LT5570 enable it to handle output ripple as high as 2dB without losing its power detection accuracy. The ripple can be further reduced for optimal transient time with an additional RC lowpass filter at the output as discussed in the next section. Output Interface The output buffer amplifier of the LT5570 is shown in Figure 9. This push-pull buffer amplifier can source 5mA current to the load and sink 2.5mA current from the load. The output impedance is determined primarily by the 100 series resistor connected to the buffer amplifier. This will prevent any over-stress on the internal devices in case the output is shorted to ground. The -3dB bandwidth of the buffer amplifier is about 2.4MHz and the full-scale rise/fall time can be as fast as
175ns. When the output is resistively terminated or open, the fastest output transient response is achieved when a large signal is applied to the RF input port. The total rise time of the LT5570 is about 0.5s and the total fall time is 8s, respectively, for full-scale pulsed RF input power. The speed of the output transient response is dictated mainly by the filtering capacitor C1 (at least 22nF) at the FLTR pin. See the detailed output transient response in the Typical Performance Characteristics section. When the RF input has AM content, residual ripple may be present at the output depending upon the low frequency content of the modulated RF signal. For example, when 4-carrier WCDMA is applied at the RF input, 36mVRMS (about 1dB) ripple is present at the output. This ripple can be reduced with a larger filtering capacitor C1 at the expense of a slower transient response.
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LT5570 APPLICATIONS INFORMATION
2.0 1.8 1.6 1.4 VOUT (V) 1.2 1.0 0.8 0.6 0.4 0.2 0 0 WITH FILTERING WITHOUT FILTERING RF PULSE OFF RF PULSE ON RF PULSE OFF AT 2140MHZ, PIN = 10dBm 200 160 120 RESIDUAL RIPPLE (mV) 80 40 0 -40 -80 -120 -160 VCC
EN 100k 100k
-200 10 20 30 40 50 60 70 80 90 100 TIMES (s)
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Figure 10. Residual ripple, Output Transient Times with Output Low-pass Filter
Figure 11. Enable Pin Simplified Circuit
Since the output amplifier of the LT5570 is capable of driving an arbitrary capacitive load, the residual ripple can be filtered at the output with a series resistor RSS and a large shunt capacitor CLOAD. See Figure 9. This lowpass filter also reduces the output noise by limiting the output noise bandwidth. When this RC network is designed properly, a fast output transient response can be maintained with reduced residual ripple. We can estimate CLOAD with an output voltage swing of 1.8V at 2140MHz. In order that the maximum 2.5mA sinking current not limit the fall time (about 8S), CLOAD can be chosen as follows. CLOAD = 2.5mA * approximate additional time/1.8V = 2.5mA * 0.25s/1.8V = 347pF Once CLOAD is determined, RSS can be chosen properly to form a RC lowpass filter with a corner frequency of 2/(RSS * CLOAD). Using 4-carrier W-CDMA as an example, Figure 10 shows the residual ripple is reduced to half from , 36mVRMS with RSS = 4.7k and CLOAD = 330pF while the fall time is slightly increased to 8.8S.
In general, the rise time of the LT5570 is much shorter than the fall time. However, when the output RC filter is used, the rise time is dominated by the time constant of this filter. Accordingly, the rise time becomes very similar to the fall time. Enable Interface A simplified schematic of the EN Pin interface is shown in Figure 11. The enable voltage necessary to turn on the LT5570 is 2V. To disable or turn off the chip, this voltage should be below 1V. It is important that the voltage applied to the EN pin should never exceed VCC by more than 0.3V. Otherwise, the supply current may be sourced through the upper ESD protection diode connected at the EN pin. Under no circumstances should voltage be applied to the EN Pin before the supply voltage is applied to the VCC pin. If this occurs, damage to the IC may result.
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LT5570 PACKAGE DESCRIPTION
DD Package 10-Lead Plastic DFN (3mm x 3mm)
(Reference LTC DWG # 05-08-1699)
R = 0.115 TYP 6 0.675 0.05 0.38 10 0.10
3.50 0.05 1.65 0.05 2.15 0.05 (2 SIDES) PACKAGE OUTLINE 0.25 0.05 0.50 BSC 2.38 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 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 PIN 1 TOP MARK (SEE NOTE 6)
3.00 0.10 (4 SIDES)
1.65 0.10 (2 SIDES)
(DD) DFN 1103
5 0.200 REF 0.75 0.05 2.38 0.10 (2 SIDES)
1 0.25 0.05 0.50 BSC
0.00 - 0.05
BOTTOM VIEW--EXPOSED PAD
5570f
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
LT5570 RELATED PARTS
PART NUMBER Infrastructure LT5514 LT5515 LT5516 LT5517 LT5518 LT5519 LT5520 LT5521 LT5522 LT5524 LT5525 LT5526 LT5527 LT5528 LT5557 LT5560 LT5568 LT5572 DESCRIPTION Ultralow Distortion, IF Amplifier/ADC Driver with Digitally Controlled Gain 1.5GHz to 2.5GHz Direct Conversion Quadrature Demodulator 0.8GHz to 1.5GHz Direct Conversion Quadrature Demodulator 40MHz to 900MHz Quadrature Demodulator 1.5GHz to 2.4GHz High Linearity Direct Quadrature Modulator 0.7GHz to 1.4GHz High Linearity Upconverting Mixer 1.3GHz to 2.3GHz High Linearity Upconverting Mixer 10MHz to 3700MHz High Linearity Upconverting Mixer 600MHz to 2.7GHz High Signal Level Downconverting Mixer Low Power, Low Distortion ADC Driver with Digitally Programmable Gain 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 Ultra-Low Power Active Mixer 700MHz to 1050MHz High Linearity Direct Quadrature Modulator COMMENTS 850MHz Bandwidth, 47dBm OIP3 at 100MHz, 10.5dB to 33dB Gain Control Range 20dBm IIP3, Integrated LO Quadrature Generator 21.5dBm IIP3, Integrated LO Quadrature Generator 21dBm IIP3, Integrated LO Quadrature Generator 22.8dBm OIP3 at 2GHz, -158.2dBm/Hz Noise Floor, 50 Single-Ended RF and LO Ports, 4-Channel W-CDMA ACPR = -64dBc at 2.14GHz 17.1dBm IIP3 at 1GHz, Integrated RF Output Transformer with 50 Matching, Single-Ended LO and RF Ports Operation 15.9dBm IIP3 at 1.9GHz, Integrated RF Output Transformer with 50 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, 50 Single-Ended RF and LO Ports 450MHz Bandwidth, 40dBm OIP3, 4.5dB to 27dB Gain Control Single-Ended 50 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, 50, 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, 50, 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 50, 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 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
5570f
1.5GHz to 2.5GHz High Linearity Direct Quadrature Modulator LT5575 800MHz to 2.7GHz High Linearity Direct Conversion I/Q Demodulator RF Power Detectors LTC(R)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
16 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 1107 * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2007

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