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LT5525 High Linearity, Low Power Downconverting Mixer
FEATURES

DESCRIPTIO
Wide Input Frequency Range: 0.8GHz to 2.5GHz* Broadband LO and IF Operation High Input IP3: +17.6dBm at 1900MHz Typical Conversion Gain: -1.9dB at 1900MHz High LO-RF and LO-IF Isolation SSB Noise Figure: 15.1dB at 1900MHz Single-Ended 50 RF and LO Interface Integrated LO Buffer: -5dBm Drive Level Low Supply Current: 28mA Typ Enable Function Single 5V Supply 16-Lead QFN (4mm x 4mm) Package
The LT(R)5525 is a low power broadband mixer optimized for high linearity applications such as point-to-point data transmission, high performance radios and wireless infrastructure systems. The device includes an internally 50 matched high speed LO amplifier driving a double-balanced active mixer core. An integrated RF buffer amplifier provides excellent LO-RF isolation. The RF input balun and all associated 50 matching components are integrated. The IF ports can be easily matched across a broad range of frequencies for use in a wide variety of applications. The LT5525 offers a high performance alternative to passive mixers. Unlike passive mixers, which require high LO drive levels, the LT5525 operates at significantly lower LO input levels and is much less sensitive to LO power level variations.
, LTC and LT are registered trademarks of Linear Technology Corporation. *Operation over a wider frequency range is achievable with reduced performance. Consult factory for more information.
APPLICATIO S

Point-to-Point Data Communication Systems Wireless Infrastructure High Performance Radios High Linearity Receiver Applications
TYPICAL APPLICATIO
High Signal Level Frequency Downconversion
0.01F EN BIAS
OUTPUT POWER (dBm/TONE)
VCC 5V DC
VCC2
VCC1 100pF
1900MHz LNA
1900MHz RF + IF + IF - RF -
150nH 1.2pF 150nH
140MHz 4:1 VGA ADC
GND LT5525 LO+ LO - LO INPUT -5dBm
5525 TA01
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IF Output Power and IM3 vs RF Input Power (Two Input Tones)
0 -10 -20 -30 -40 -50 -60 -70 -80 -90 IM3 TA = 25C fRF = 1900MHz fLO = 1760MHz fIF = 140MHz PLO = -5dBm -10 -15 -5 RF INPUT POWER (dBm/TONE) 0
5525 TA02
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POUT
-100 -20
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1
LT5525
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW
LO+ LO- NC NC
Supply Voltage ...................................................... 5.5V Enable Voltage ............................... -0.3V to VCC + 0.3V LO Input Power ............................................... +10dBm LO+ to LO- Differential DC Voltage ......................... 1V LO+ and LO- Common Mode DC Voltage... -0.5V to VCC RF Input Power ................................................ +10dBm RF+ to RF- Differential DC Voltage ..................... 0.13V RF+ and RF- Common Mode DC Voltage ... -0.5V to VCC IF+ and IF- Common Mode DC Voltage ................... 5.5V Operating Temperature Range ................ - 40C to 85C Storage Temperature Range ................. - 65C to 125C Junction Temperature (TJ)................................... 125C
ORDER PART NUMBER
12 GND
16 15 14 13 NC 1 RF + 2 RF - 3 NC 4 5
EN
LT5525EUF
17
11 IF+ 10 IF- 9 GND
6
VCC1
7
VCC2
8
NC
UF PART MARKING 5525
UF PACKAGE 16-LEAD (4mm x 4mm) PLASTIC QFN
TJMAX = 125C, JA = 37C/W EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB. NC PINS SHOULD BE GROUNDED
Consult LTC Marketing for parts specified with wider operating temperature ranges.
DC ELECTRICAL CHARACTERISTICS
VCC = 5V, EN = 3V, TA = 25C (Note 3), unless otherwise noted. Test circuit shown in Figure 1.
PARAMETER Power Supply Requirements (VCC) Supply Voltage Supply Current Shutdown Current Enable (EN) Low = Off, High = On EN Input High Voltage (On) EN Input Low Voltage (Off) Enable Pin Input Current Turn-On Time (Note 5) Turn-Off Time (Note 5) EN = 5V EN = 0V 55 0.1 3 6 3 0.3 V V A A s s (Note 6) VCC = 5V EN = Low 3.6 5 28 5.3 33 100 V mA A CONDITIONS MIN TYP MAX UNITS
AC ELECTRICAL CHARACTERISTICS
PARAMETER RF Input Frequency Range (Note 4) LO Input Frequency Range (Note 4) IF Output Frequency Range (Note 4)
(Notes 2, 3)
MIN TYP 800 to 2500 500 to 3000 0.1 to 1000 MAX UNITS MHz MHz MHz
CONDITIONS Requires RF Matching Below 1300MHz Requires IF Matching
VCC = 5V, EN = 3V, TA = 25C. Test circuit shown in Figure 1. (Notes 2, 3)
PARAMETER RF Input Return Loss LO Input Return Loss IF Output Return Loss LO Input Power CONDITIONS ZO = 50 ZO = 50, External DC Blocks ZO = 50, External Match MIN TYP 15 15 15 -10 to 0 MAX UNITS dB dB dB dBm
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LT5525
AC ELECTRICAL CHARACTERISTICS
PARAMETER Conversion Gain CONDITIONS fRF = 900MHz fRF = 1900MHz fRF = 2100MHz fRF = 2500MHz TA = -40C to 85C fRF = 900MHz fRF = 1900MHz fRF = 2100MHz fRF = 2500MHz fRF = 900MHz fRF = 1900MHz fRF = 2100MHz fRF = 2500MHz
VCC = 5V, EN = 3V, TA = 25C, PRF = -15dBm (-15dBm/tone for 2-tone IIP3 tests, f = 1MHz), fLO = fRF - 140MHz, PLO = -5dBm, IF output measured at 140MHz, unless otherwise noted. Test circuit shown in Figure 1. (Notes 2, 3)
MIN TYP -2.6 -1.9 -2.0 -2.0 -0.020 21.0 17.6 17.6 12.0 14.0 15.1 15.6 15.6 -50 -43 -50 -39 >38 62 42 40 33 7.6 4 4 3 -63 -53 -45 -42 -74 -59 -59 -60 MAX UNITS dB dB dB dB dB/C dBm dBm dBm dBm dB dB dB dB dBm dBm dBm dBm dB dB dB dB dB dBm dBm dBm dBm dBc dBc dBc dBc dBc dBc dBc dBc
Conversion Gain vs Temperature Input 3rd Order Intercept
Single Sideband Noise Figure
LO to RF Leakage LO to IF Leakage RF to LO Isolation RF to IF Isolation
fLO = 500MHz to 1000MHz fLO = 1000MHz to 3000MHz fLO = 500MHz to 1400MHz fLO = 1400MHz to 3000MHz fRF = 500MHz to 3000MHz fRF = 900MHz fRF = 1900MHz fRF = 2100MHz fRF = 2500MHz fRF = 900MHz fRF = 1900MHz fRF = 2100MHz fRF = 2500MHz 900MHz: fRF = 830MHz at -15dBm 1900MHz: fRF = 1830MHz at -15dBm 2100MHz: fRF = 2030MHz at -15dBm 2500MHz: fRF = 2430Hz at -15dBm 900MHz: fRF = 806.67MHz at -15dBm 1900MHz: fRF = 1806.67MHz at -15dBm 2100MHz: fRF = 2006.67MHz at -15dBm 2500MHz: fRF = 2406.67Hz at -15dBm
Input 1dB Compression
2RF-2LO Output Spurious Product (fRF = fLO + fIF/2)
3RF-3LO Output Spurious Product (fRF = fLO + fIF/3)
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The performance is measured with the test circuit shown in Figure 1. For 900MHz measurements, C1 = 3.9pF. For all other measurements, C1 is not used. Note 3: Specifications over the -40C to 85C temperature range are assured by design, characterization and correlation with statistical process controls.
Note 4: Operation over a wider frequency range is possible with reduced performance. Consult the factory for information and assistance. Note 5: Turn-on and turn-off times correspond to a change in the output level of 40dB. Note 6: The part is operable below 3.6V with reduced performance.
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LT5525
VCC = 5V, EN = 3V, TA = 25C, fRF = 1900MHz, PRF = -15dBm (-15dBm/tone for 2-tone IIP3 tests, f = 1MHz), fLO = fRF - 140MHz, PLO = -5dBm, IF output measured at 140MHz, unless otherwise noted. Test circuit shown in Figure 1. Conversion Gain and IIP3 vs RF Frequency (Low Side LO)
25 20 25 20 IIP3 GAIN (dB), IIP3 (dBm) 15 10 5 0 GAIN 25C 85C -40C NOISE FIGURE (dB)
TYPICAL AC PERFOR A CE CHARACTERISTICS
Conversion Gain and IIP3 vs RF Frequency (High Side LO)
IIP3
GAIN (dB), IIP3 (dBm)
15 10 5 0 GAIN 25C 85C -40C
-5 900 1100 1300 1500 1700 1900 2100 2300 2500 RF FREQUENCY (MHz)
5525 G01
Conversion Gain and IIP3 vs LO Input Power
25 20
GAIN (dB), IIP3 (dBm)
IIP3
17 16 15 14 13
LEAKAGE (dBm)
15 10 5 0
NOISE FIGURE (dB)
25C 85C -40C GAIN
-5 -16 -14 -12 -10 -8 -6 -4 -2 0 LO INPUT POWER (dBm)
2
5525 G04
Conversion Gain and IIP3 vs Supply Voltage
25 20 0 -5 RETURN LOSS (dB)
OUTPUT POWER (dBm/TONE)
GAIN (dB), IIP3 (dBm)
15 10 IIP3 5 0 GAIN
25C 85C -40C
-5 2.8
3.2
4.4 4 4.8 3.6 SUPPLY VOLTAGE (V)
5.2
5525 G07
4
UW
4
SSB NF vs RF Frequency
20 19 18 17 16 15 14 13 12 11 LOW SIDE LO HIGH SIDE LO
-5 900 1100 1300 1500 1700 1900 2100 2300 2500 RF FREQUENCY (MHz)
5525 G02
12 900 1100 1300 1500 1700 1900 2100 2300 2500 RF FREQUENCY (MHz)
5525 G03
SSB Noise Figure vs LO Input Power
20 19 18 25C 85C -40C 0 -10 -20 -30 -40 -50 -60 -70 -80 -90 0 2
LO-IF, LO-RF and RF-LO Leakage vs Frequency
LO-RF RF-LO LO-IF
12 -14 -12 -10 -8 -6 -4 -2 LO INPUT POWER (dBm)
-100 500
1000
2000 2500 1500 FREQUENCY (MHz)
3000
5525 G06
5525 G05
RF, LO and IF Port Return Loss vs Frequency
0 -10 -20 -30 -40 -50 -60 -70 -80 -90
IF Output Power and IM3 vs RF Input Power (Two Input Tones)
RF -10 LO -15 -20 IF -25 -30
POUT
IM3 25C 85C -40C -10 -15 -5 RF INPUT POWER (dBm/TONE) 0
5525 G09
5.6
0
500
1000 1500 2000 FREQUENCY (MHz)
2500
3000
-100 -20
5525 G08
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LT5525
VCC = 5V, EN = 3V, TA = 25C, fRF = 1900MHz, PRF = -15dBm (-15dBm/tone for 2-tone IIP3 tests, f = 1MHz), fLO = fRF - 140MHz, PLO = -5dBm, IF output measured at 140MHz, unless otherwise noted. Test circuit shown in Figure 1. IFOUT, 2 x 2 and 3 x 3 Spurs vs RF Input Power
10 0 -10
OUTPUT POWER (dBm)
-30
TYPICAL AC PERFOR A CE CHARACTERISTICS
IF OUT fRF = 1900MHz
OUTPUT POWER (dBm)
-20 -30 -40 -50 -60 -70 -80 -90 2RF-2LO fRF = 1830MHz TA = 25C fLO = 1760MHz fIF = 140MHz -15 -10 -5 RF INPUT POWER (dBm) 0
5525 G10
-100 -20
TYPICAL DC PERFOR A CE CHARACTERISTICS
Supply Current vs Supply Voltage
32 30
SUPPLY CURRENT (mA)
20
28 26 24 22 20 18 16 14 2.8 3.2 3.6 4 4.4 4.8 SUPPLY VOLTAGE (V) 25C 85C -40C 5.2 5.6
SHUTDOWN CURRENT (A)
UW
UW
2 x 2 and 3 x 3 Spurs vs LO Input Power
-40 -50 -60 -70 -80 -90 -100 -16 3RF-3LO fRF = 1806.67MHz TA = 25C fLO = 1760MHz fIF = 140MHz
3RF-3LO fRF = 1806.67MHz
2RF-2LO fRF = 1830MHz
-12
-8
-4
0
4
5525 G11
LO INPUT POWER (dBm)
Test circuit shown in Figure 1.
Shutdown Current vs Supply Voltage
25C 85C -40C
15
10
5
0 2.8 3.2 3.6 4 4.4 4.8 SUPPLY VOLTAGE (V) 5.2 5.6
5525 G12
5525 G13
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LT5525
PI FU CTIO S
NC (Pins 1, 4, 8, 13, 16): Not Connected Internally. These pins should be grounded on the circuit board for improved LO-to-RF and LO-to-IF isolation. RF+, RF- (Pins 2, 3): Differential Inputs for the RF Signal. One RF input pin may be DC connected to a low impedance ground to realize a 50 single-ended input at the other RF pin. No external matching components are required. A DC voltage should not be applied across these pins, as they are internally connected through a transformer winding. EN (Pin 5): Enable Pin. When the input voltage is higher than 3V, the mixer circuits supplied through Pins 6, 7, 10 and 11 are enabled. When the input voltage is less than 0.3V, all circuits are disabled. Typical enable pin input current is 55A for EN = 5V and 0.1A when EN = 0V. VCC1 (Pin 6): Power Supply Pin for the LO Buffer Circuits. Typical current consumption is 11mA. This pin should be externally connected to the other VCC pins and decoupled with 1F and 0.01F capacitors. VCC2 (Pin 7): Power Supply Pin for the Bias Circuits. Typical current consumption is 2.5mA. This pin should be externally connected to the other VCC pins and decoupled with 1F and 0.01F capacitors. GND (Pins 9, 12): Ground. These pins are internally connected to the Exposed Pad for better isolation. They should be connected to ground on the circuit board, though they are not intended to replace the primary grounding through the Exposed Pad of the package. IF- and IF+ (Pins 10, 11): Differential Outputs for the IF Signal. An impedance transformation may be required to match the outputs. These pins must be connected to VCC through impedance matching inductors, RF chokes or a transformer center-tap. LO-, LO+ (Pins 14, 15): Differential Inputs for the Local Oscillator Signal. The LO input is internally matched to 50. The LO can be driven with a single-ended source through either LO input pin, with the other LO input pin connected to ground. There is an internal DC resistance across these pins of approximately 480. Thus, a DC blocking capacitor should be used if the signal source has a DC voltage present. Exposed Pad (Pin 17): Circuit Ground Return for the Entire IC. This must be soldered to the printed circuit board ground plane.
BLOCK DIAGRA
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17 EXPOSED PAD
15 LO+
14 LO-
HIGH SPEED LO BUFFER
+
2
RF
LINEAR AMPLIFIER
GND IF+ IF- DOUBLEBALANCED MIXER GND
12 11 10 9
3
RF -
BIAS EN 5 7 VCC2 6 VCC1
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LT5525
TEST CIRCUITS
LOIN 1760MHz 16 C1 OPTIONAL RFIN 1900MHz 1 2 17 NC NC RF
+
0.018" 0.062"
ER = 4.4
RF GND DC
15 LO
+
14 LO-
13 NC GND IF 12 L3
0.018"
GND
T2 C4 1 2 3 4 IFOUT 140MHz 5
+ 11
LT5525 3 4 RF - NC EN EN 900MHz INPUT MATCHING: C1: 3.9pF 5 6 7
IF - GND
10 9
C3 L2
VCC1 VCC2 NC 8
5526 F01
VCC
C2
C8
REF DES C1 C2 C3 C4 C8 L2, L3 T2
VALUE -- 0.01F 1.2pF 100pF 1F 150nH 4:1
SIZE 0402 0402 0402 0402 0603 1608 SM-22
PART NUMBER Frequency Dependent AVX 04023C103JAT AVX 04025A1R2BAT AVX 04025A101JAT Taiyo Yuden LMK107BJ105MA Toko LL1608-FSR15J M/A-COM ETC4-1-2
Figure 1. Test Schematic
APPLICATIO S I FOR ATIO
The LT5525 consists of a double-balanced mixer, RF balun, RF buffer amplifier, high speed limiting LO buffer and bias/enable circuits. The IC has been optimized for downconverter applications with RF input signals from 0.8GHz to 2.5GHz and LO signals from 500MHz to 3GHz. With proper matching, the IF output can be operated at frequencies from 0.1MHz to 1GHz. Operation over a wider frequency range is possible, though with reduced performance. The RF, LO and IF ports are all differential, though the RF and LO ports are internally matched to 50 for singleended drive. The LT5525 is characterized and production tested using single-ended RF and LO inputs. Low side or high side LO injection can be used.
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RF Input Port The mixer's RF input, shown in Figure 2, consists of an integrated balun and a high linearity differential amplifier. The primary terminals of the balun are connected to the RF+ and RF- pins (Pins 2 and 3, respectively). The secondary side of the balun is internally connected to the amplifier's differential inputs. For single-ended operation, the RF+ pin is grounded and the RF- pin becomes the RF input. It is also possible to ground the RF- pin and drive the RF+ pin, if desired. If the RF source has a DC voltage present, then a coupling capacitor must be used in series with the RF input pin. Otherwise, excessive DC current could damage the primary winding of the balun.
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LT5525
APPLICATIO S I FOR ATIO
2 RF+
LT5525
GAIN AND NF (dB), IIP3 (dBm)
OPTIONAL SERIES REACTANCE FOR LOW BAND OR HIGH BAND RFIN MATCHING 3
RF-
Figure 2. RF Input Schematic
As shown in Figure 3, the RF input return loss with no external matching is greater than 12dB from 1.3GHz to 2.3GHz. The RF input match can be shifted down to 800MHz by adding a series 3.9pF capacitor at the RF input. A series 1.2nH inductor can be added to shift the match up to 2.5GHz. Measured return losses with these external components are also shown in Figure 3.
0 -5 RETURN LOSS (dB) -10 -15 -20 SERIES 1.2nH -25 SERIES 3.9pF -30 500 1000 1500 2000 2500 RF FREQUENCY (MHz) 3000
5525 F03
NO RF MATCHING
Figure 3. RF Input Return Loss Without and with External Matching Components
Figure 4 illustrates the typical conversion gain, IIP3 and NF performance of the LT5525 when the RF input match is shifted lower in frequency using an external series 3.9pF capacitor on the RF input. RF input impedance and reflection coefficient (S11) versus frequency are shown in Table 1. The listed data is referenced to the RF- pin with the RF+ pin grounded (no external matching). This information can be used to simulate board-level interfacing to an input filter, or to design a broadband input matching network.
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25 20 15 SSB NF 10 5 0 GAIN -5 800 850 900 950 1000 1050 1100 1150 1200 RF FREQUENCY (MHz)
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IIP3
TA = 25C fIF = 140MHz LOW SIDE LO HIGH SIDE LO
5525 F02
Figure 4. Typical Gain, IIP3 and NF with Series 3.9pF Matching Capacitor Table 1. RF Port Input Impedance vs Frequency
FREQUENCY (MHz) 50 500 700 900 1100 1300 1500 1700 1900 2100 2300 2500 2700 3000 INPUT IMPEDANCE 10.4 + j2.63 18.1 + j23.7 25.8 + j30.7 36.5 + j34.5 48.4 + j33.3 59.5 + j25.7 65.9 + j13.1 65.0 - j1.0 59.0 - j12.2 50.2 - j19.0 41.8 - j22.1 34.9 - j22.7 29.1 - j21.9 23.2 - j19.1 REFLECTION COEFFICIENT MAG ANGLE 0.675 174 0.551 124 0.478 106 0.398 90 0.321 74 0.244 57 0.177 33 0.131 -3 0.138 -47 0.187 -79 0.250 -97 0.311 -109 0.369 -118 0.435 -130
A broadband RF input match can be easily realized by using both the series capacitor and series inductor as shown in Figure 5. This network provides good return loss at both lower and higher frequencies simultaneously, while maintaining good mid-band return loss. The broadband return loss is plotted in Figure 6. The return loss is better than 12dB from 700MHz to 2.6GHz using the element values of Figure 5. LO Input Port The LO buffer amplifier consists of high speed limiting differential amplifiers designed to drive the mixer core for high linearity. The LO+ and LO- pins are designed for
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LT5525
APPLICATIO S I FOR ATIO
2 RF+
LT5525
RETURN LOSS (dB)
5525 F05
RFIN
C5 4.7pF
L3 1.5nH 3
RF-
Figure 5. Wideband RF Input Matching
0 -5 RETURN LOSS (dB) -10 -15 -20 -25 -30 500 SERIES 1.5nH AND 4.7pF NO EXTERNAL RF MATCHING
1000
1500 2000 2500 RF FREQUENCY (MHz)
3000
5525 F06
Figure 6. RF Input Return Loss Using Wideband Matching Network
single-ended drive, though differential drive can be used if desired. The LO input is internally matched to 50. A simplified schematic for the LO input is shown in Figure 7. Measured return loss is shown in Figure 8. If the LO source has a DC voltage present, then a coupling capacitor should be used in series with the LO input pin due to the internal resistive match.
14 LO- 20pF LT5525
VCC LOIN 50 15
480 20pF
54
LO+
5525 F07
Figure 7. LO Input Schematic Figure 9. IF Output with External Matching
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0 -5 -10 -15 -20 0 500 1000 1500 2000 FREQUENCY (MHz) 2500 3000
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Figure 8. LO Input Return Loss
The LO port input impedance and reflection coefficient (S11) versus frequency are shown in Table 2. The listed data is referenced to the LO+ pin with the LO- pin grounded.
Table 2. Single-Ended LO Input Impedance
FREQUENCY (MHz) 100 250 500 1000 1500 2000 2500 3000 INPUT IMPEDANCE 93.1 - j121 55.8 - j54 47.7 - j28 42.3 - j14 38.5 - j9.3 35.8 - j7.8 34.8 - j7.8 34.2 - j8.7 REFLECTION COEFFICIENT MAG ANGLE 0.686 -30 0.457 -57 0.276 -79 0.171 -110 0.166 -135 0.187 -146 0.281 -148 0.214 -149
IF Output Port A simplified schematic of the IF output circuit is shown in Figure 9. The output pins, IF+ and IF-, are internally connected to the collectors of the mixer switching transistors. Both pins must be biased at the supply voltage, which can be applied through the center-tap of a transformer or
LT5525 IF+ 575 0.7pF IF- VCC
5525 F09
L3 11 C3 VCC L2 10
T2 4:1
IFOUT
9
LT5525
APPLICATIO S I FOR ATIO
through impedance-matching inductors. Each IF pin draws about 7.5mA of supply current (15mA total). For optimum single-ended performance, these differential outputs must be combined externally through an IF transformer or balun. An equivalent small-signal model for the output is shown in Figure 10. The output impedance can be modeled as a 574 resistor (RIF) in parallel with a 0.7pF capacitor. For most applications, the bond-wire inductance (0.7nH per side) can be ignored. The external components, C3, L2 and L3 form an impedance transformation network to match the mixer output impedance to the input impedance of transformer T2. The values for these components can be estimated using the equations below, along with the impedance values listed in Table 3. As an example, at an IF frequency of 140MHz and RL = 200 (using a 4:1 transformer for T2 with an external 50 load), n = RIF/RL = 574/200 = 2.87 Q = (n - 1) = 1.368 XC = RIF/Q = 420 C = 1/( * XC) = 2.71pF C3 = C - CIF = 2.01pF XL = RL * Q = 274 L2 = L3 = XL/2 = 156nH
Table 3. IF Differential Impedance (Parallel Equivalent)
FREQUENCY (MHz) 70 140 240 450 750 860 1000 1250 1500 OUTPUT IMPEDANCE 575|| - j3.39k 574|| - j1.67k 572|| - j977 561|| - j519 537|| - j309 525|| - j267 509|| - j229 474|| - j181 435|| - j147 REFLECTION COEFFICIENT MAG ANGLE 0.840 -1.8 0.840 -3.5 0.840 -5.9 0.838 -11.1 0.834 -18.6 0.831 -21.3 0.829 -24.8 0.822 -31.3 0.814 -38.0
Low Cost Output Match For low cost applications in which the required fractional bandwidth of the IF output is less than 25%, it may be possible to replace the output transformer with a lumped-
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LT5525 0.7nH IF+ L3 11 C3 0.7nH IF- L2 10 RL 200 RIF 574 CIF 0.7pF
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Figure 10. IF Output Small Signal Model
element network. This circuit is shown in Figure 11, where L11, L12, C11 and C12 form a narrowband bridge balun. These element values are selected to realize a 180 phase shift at the desired IF frequency, and can be estimated using the equations below. In this case, the load resistance, RL, is 50.
L11 = L12 =
RIF * RL 1 C11 = C12 = RIF * RL
Inductor L13 or L14 provides a DC path between VCC and the IF+ pin. Only one of these inductors is required. Low cost multilayer chip inductors are adequate for L11, L12 and L13. If L14 is used instead of L13, a larger value is usually required, which may require the use of a wirewound inductor. Capacitor C13 is a DC block which can also be used to adjust the impedance match. Capacitor C14 is a bypass capacitor.
IF+
C12 L11 C13 L14 OPT C11 L13 OPT C14 IFOUT 50
IF- L12 VCC
5525 F11
Figure 11. Narrowband Bridge IF Balun
Actual component values for IF frequencies of 240MHz, 360MHz and 450MHz are listed in Table 4. Typical IF port return loss for these examples is shown in Figure 12.
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LT5525
APPLICATIO S I FOR ATIO
Conversion gain and IIP3 performance with an RF frequency of 1900MHz are plotted vs IF frequency in Figure 13. These results show that the usable IF bandwidth for the lumped element balun is greater than 60MHz, assuming tight tolerance matching components. Contact the factory for applications assistance with this circuit.
0 20 IIP3
-5 GAIN (dB), IIP3 (dBm)
15
RETURN LOSS (dB)
-10
10
IIP3 (dBm)
-15
5 GAIN
-20
0
-25 200
250
300 350 400 FREQUENCY (MHz)
450
500
5525 F12
-5 200
Figure 12. Typical IF Return Loss Performance with 240MHz, 360MHz and 450MHz Lumped Element Baluns
Figure 13. Typical Gain and IIP3 vs IF Frequency with 240MHz, 360MHz and 450MHz Lumped Element Baluns
TYPICAL APPLICATIO S
Evaluation Board Layouts Top Layer Silkscreen Top Layer Metal
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.
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Table 4. Component Values for Lumped Balun
IF FREQ (MHz) 240 360 450 L11, L12 (nH) C11, C12 (pF) C13 (pF) L14 (nH) 100 3.9 100 560 68 2.7 10 270 56 2.2 8.2 180
20 19 18 17 TA = 25C fLO = fRF - fIF fRF = 1900MHz PLO = -5dBm PRF = -15dBm 16 15 14 13 TA = 25C 12 f = f - f LO RF IF 11 PLO = -5dBm PRF = -15dBm 10 1200 1400 1600 1800 2000 2200 RF FREQUENCY (MHz) 240MHz 360MHz 450MHz 2400 2600
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250
300 350 400 IF FREQUENCY (MHz)
450
500
5525 F13
Figure 14. Typical IIP3 vs RF Frequency with Lumped Element Baluns and IF Frequencies of 240MHz, 360MHz and 450MHz
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LT5525
PACKAGE DESCRIPTIO
4.35 0.05 2.15 0.05 (4 SIDES) 2.90 0.05
0.30 0.05 0.65 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WGGC) 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
RELATED PARTS
PART NUMBER Infrastructure LT5512 LT5514 LT5519 LT5520 LT5521 LT5522 LT5526 DESCRIPTION DC-3GHz High Signal Level Down Converting Mixer Ultralow Distortion, IF Amplifier/ADC Driver with Digitally Controlled Gain 0.7GHz to 1.4GHz High Linearity Upconverting Mixer 1.3GHz to 2.3GHz High Linearity Upconverting Mixer 3.7GHz Very High Linearity Mixer 600MHz to 2.7GHz High Signal Level Downconverting Mixer High Linearity, Low Power Downconverting Mixer COMMENTS 21dBm IIP3, Integrated LO Buffer 850MHz Bandwidth, 47dBm OIP3 at 100MHz, 10.5dB to 33dB Gain Control Range 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, 12.5dB SSBNF, -42dBm LO Leakage, Supply Voltage = 3.15V to 5.25V 4.5V to 5.25V Supply, 25dBm IIP3 at 900MHz, NF = 12.5dB, 50 Single-Ended RF and LO Ports 16.5dBm IIP3 at 900MHz, NF = 11dB, Supply Current = 28mA, 3.6V to 5.3V Supply 44dB Dynamic Range, Temperature Compensated, SC70 Package Precision VOUT Offset Control, Adjustable Gain and Offset 1dB Output Variation over Temperature, 38ns Response Time 12MHz Baseband BW, Precision Offset with Adjustable Gain and Offset 500MHz BW S/H, 71.8dB SNR, 87dB SFDR 500MHz BW S/H, 75.5dB SNR, 90dB SFDR, 2.25VP-P or 1.35VP-P Input Ranges Low Power 775MHz BW S/H, 61dB SNR, 75dB SFDR 0.5V or 1V Input Low Power 775MHz BW S/H, 61dB SNR, 75dB SFDR 0.5V or 1V Input
5525f LT/TP 1004 1K * PRINTED IN THE USA
RF Power Detectors LTC5508 300MHz to 7GHz RF Power Detector LTC5532 300MHz to 7GHz Precision RF Power Detector LT5534 50MHz to 3GHz RF Power Detector with 60dB Dynamic Range LTC5535 600MHz to 7GHz RF Power Detector Wide Bandwidth ADCs LTC1749 12-Bit, 80Msps ADC LTC1750 14-Bit, 80Msps ADC LTC2222/ LTC2223 LTC2224/ LTC2234 12-Bit, 105Msps/80Msps ADC 10-Bit/12-Bit, 135Msps ADC
12
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
U
UF Package 16-Lead Plastic QFN (4mm x 4mm)
(Reference LTC DWG # 05-08-1692)
4.00 0.10 (4 SIDES) 0.72 0.05 PIN 1 TOP MARK (NOTE 6) 0.75 0.05 R = 0.115 TYP 0.55 0.20 15 16 1 2.15 0.10 (4-SIDES) 2 PACKAGE OUTLINE 0.200 REF 0.00 - 0.05
(UF) QFN 1103
0.30 0.05 0.65 BSC BOTTOM VIEW--EXPOSED PAD
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
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2004

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