LINER LT5525EUF High linearity, low power downconverting mixer Datasheet

LT5525
High Linearity, Low Power
Downconverting Mixer
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FEATURES
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DESCRIPTIO
The LT®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 50Ω
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 50Ω 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.
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 50Ω RF and LO Interface
Integrated LO Buffer: –5dBm Drive Level
Low Supply Current: 28mA Typ
Enable Function
Single 5V Supply
16-Lead QFN (4mm × 4mm) Package
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.
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APPLICATIO S
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Point-to-Point Data Communication Systems
Wireless Infrastructure
High Performance Radios
High Linearity Receiver Applications
, 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.
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TYPICAL APPLICATIO
High Signal Level Frequency Downconversion
0.01µF
EN
VCC2
IF Output Power and IM3 vs
RF Input Power (Two Input Tones)
VCC
5V DC
0
VCC1
–10
100pF
1900MHz
1900MHz
LNA
RF +
IF +
IF –
RF –
GND
LT5525
1.2pF
150nH
4:1
VGA
ADC
–20
–30
POUT
–40
–50
–60
–70
–80
–90
IM3
–100
–20
LO+ LO –
LO INPUT
–5dBm
150nH
140MHz
OUTPUT POWER (dBm/TONE)
BIAS
TA = 25°C
fRF = 1900MHz
fLO = 1760MHz
fIF = 140MHz
PLO = –5dBm
–10
–15
–5
RF INPUT POWER (dBm/TONE)
0
5525 TA01
5525 TA02
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LT5525
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ABSOLUTE MAXIMUM RATINGS
PACKAGE/ORDER INFORMATION
(Note 1)
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 ................ – 40°C to 85°C
Storage Temperature Range ................. – 65°C to 125°C
Junction Temperature (TJ)................................... 125°C
ORDER PART
NUMBER
NC
LO–
LO+
NC
TOP VIEW
16 15 14 13
NC 1
LT5525EUF
12 GND
RF + 2
11 IF+
17
RF – 3
10 IF–
6
7
8
EN
VCC2
NC
9 GND
5
VCC1
NC 4
UF PART
MARKING
UF PACKAGE
16-LEAD (4mm × 4mm) PLASTIC QFN
5525
TJMAX = 125°C, θJA = 37°C/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 = 25°C (Note 3), unless otherwise noted. Test circuit shown in Figure 1.
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage
(Note 6)
3.6
5
5.3
V
Supply Current
VCC = 5V
33
mA
Shutdown Current
EN = Low
100
µA
Power Supply Requirements (VCC)
28
Enable (EN) Low = Off, High = On
EN Input High Voltage (On)
3
V
EN Input Low Voltage (Off)
Enable Pin Input Current
0.3
EN = 5V
EN = 0V
V
55
0.1
µA
µA
Turn-On Time (Note 5)
3
µs
Turn-Off Time (Note 5)
6
µs
AC ELECTRICAL CHARACTERISTICS
(Notes 2, 3)
PARAMETER
CONDITIONS
RF Input Frequency Range (Note 4)
Requires RF Matching Below 1300MHz
MIN
LO Input Frequency Range (Note 4)
IF Output Frequency Range (Note 4)
Requires IF Matching
TYP
MAX
UNITS
800 to 2500
MHz
500 to 3000
MHz
0.1 to 1000
MHz
VCC = 5V, EN = 3V, TA = 25°C. Test circuit shown in Figure 1. (Notes 2, 3)
PARAMETER
CONDITIONS
RF Input Return Loss
ZO = 50Ω
15
dB
LO Input Return Loss
ZO = 50Ω, External DC Blocks
15
dB
IF Output Return Loss
ZO = 50Ω, External Match
15
dB
LO Input Power
MIN
TYP
–10 to 0
MAX
UNITS
dBm
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LT5525
AC ELECTRICAL CHARACTERISTICS
VCC = 5V, EN = 3V, TA = 25°C, 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)
PARAMETER
CONDITIONS
Conversion Gain
fRF = 900MHz
fRF = 1900MHz
fRF = 2100MHz
fRF = 2500MHz
MIN
TYP
–2.6
–1.9
–2.0
–2.0
MAX
UNITS
dB
dB
dB
dB
Conversion Gain vs Temperature
TA = –40°C to 85°C
–0.020
dB/°C
Input 3rd Order Intercept
fRF = 900MHz
fRF = 1900MHz
fRF = 2100MHz
fRF = 2500MHz
21.0
17.6
17.6
12.0
dBm
dBm
dBm
dBm
Single Sideband Noise Figure
fRF = 900MHz
fRF = 1900MHz
fRF = 2100MHz
fRF = 2500MHz
14.0
15.1
15.6
15.6
dB
dB
dB
dB
LO to RF Leakage
fLO = 500MHz to 1000MHz
fLO = 1000MHz to 3000MHz
≤–50
≤–43
dBm
dBm
LO to IF Leakage
fLO = 500MHz to 1400MHz
fLO = 1400MHz to 3000MHz
≤–50
≤–39
dBm
dBm
RF to LO Isolation
fRF = 500MHz to 3000MHz
>38
dB
RF to IF Isolation
fRF = 900MHz
fRF = 1900MHz
fRF = 2100MHz
fRF = 2500MHz
62
42
40
33
dB
dB
dB
dB
Input 1dB Compression
fRF = 900MHz
fRF = 1900MHz
fRF = 2100MHz
fRF = 2500MHz
7.6
4
4
3
dBm
dBm
dBm
dBm
2RF-2LO Output Spurious Product
(fRF = fLO + fIF/2)
900MHz: fRF = 830MHz at –15dBm
1900MHz: fRF = 1830MHz at –15dBm
2100MHz: fRF = 2030MHz at –15dBm
2500MHz: fRF = 2430Hz at –15dBm
–63
–53
–45
–42
dBc
dBc
dBc
dBc
3RF-3LO Output Spurious Product
(fRF = fLO + fIF/3)
900MHz: fRF = 806.67MHz at –15dBm
1900MHz: fRF = 1806.67MHz at –15dBm
2100MHz: fRF = 2006.67MHz at –15dBm
2500MHz: fRF = 2406.67Hz at –15dBm
–74
–59
–59
–60
dBc
dBc
dBc
dBc
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 –40°C to 85°C 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
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TYPICAL AC PERFOR A CE CHARACTERISTICS
VCC = 5V, EN = 3V, TA = 25°C, 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)
Conversion Gain and IIP3
vs RF Frequency (High Side LO)
25
SSB NF vs RF Frequency
25
20
19
20
IIP3
10
25°C
85°C
–40°C
5
GAIN
15
10
25°C
85°C
–40°C
5
0
17
NOISE FIGURE (dB)
15
0
18
IIP3
GAIN (dB), IIP3 (dBm)
GAIN (dB), IIP3 (dBm)
20
16
HIGH SIDE LO
15
14
LOW SIDE LO
13
GAIN
12
11
–5
900 1100 1300 1500 1700 1900 2100 2300 2500
RF FREQUENCY (MHz)
–5
900 1100 1300 1500 1700 1900 2100 2300 2500
RF FREQUENCY (MHz)
5525 G01
5525 G02
Conversion Gain and IIP3
vs LO Input Power
20
10
25°C
85°C
–40°C
0
0
–10
–20
18
–30
LEAKAGE (dBm)
NOISE FIGURE (dB)
GAIN (dB), IIP3 (dBm)
IIP3
LO-IF, LO-RF and RF-LO Leakage
vs Frequency
25°C
85°C
–40°C
19
20
5
5525 G03
SSB Noise Figure
vs LO Input Power
25
15
12
900 1100 1300 1500 1700 1900 2100 2300 2500
RF FREQUENCY (MHz)
17
16
15
–40
–70
2
–90
12
–14 –12 –10 –8 –6 –4 –2
LO INPUT POWER (dBm)
4
LO-IF
–80
13
–5
–16 –14 –12 –10 –8 –6 –4 –2 0
LO INPUT POWER (dBm)
RF-LO
–60
14
GAIN
LO-RF
–50
5525 G04
0
2
–100
500
1000
2000
2500
1500
FREQUENCY (MHz)
5525 G06
5525 G05
Conversion Gain and IIP3
vs Supply Voltage
RF, LO and IF Port Return Loss
vs Frequency
25
0
20
–5
3000
IF Output Power and IM3 vs RF
Input Power (Two Input Tones)
0
10
25°C
85°C
–40°C
IIP3
5
0
OUTPUT POWER (dBm/TONE)
15
RETURN LOSS (dB)
GAIN (dB), IIP3 (dBm)
–10
RF
–10
LO
–15
–20
IF
GAIN
–25
–20
–30
POUT
–40
–50
–60
–70
–80
IM3
25°C
85°C
–40°C
–90
–5
2.8
–30
3.2
4.4
4
4.8
3.6
SUPPLY VOLTAGE (V)
5.2
5.6
5525 G07
0
500
1000 1500 2000
FREQUENCY (MHz)
2500
3000
5525 G08
–100
–20
–10
–15
–5
RF INPUT POWER (dBm/TONE)
0
5525 G09
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LT5525
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TYPICAL AC PERFOR A CE CHARACTERISTICS
VCC = 5V, EN = 3V, TA = 25°C, 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 × 2 and 3 × 3 Spurs
vs RF Input Power
2 × 2 and 3 × 3 Spurs
vs LO Input Power
10
–30
0
IF OUT
fRF = 1900MHz
OUTPUT POWER (dBm)
OUTPUT POWER (dBm)
–10
–40
–20
–30
3RF-3LO
fRF = 1806.67MHz
–40
–50
–60
–70
2RF-2LO
fRF = 1830MHz
–80
TA = 25°C
fLO = 1760MHz
fIF = 140MHz
–90
–100
–20
–15
–10
–5
RF INPUT POWER (dBm)
TA = 25°C
fLO = 1760MHz
fIF = 140MHz
–50
–60
2RF-2LO
fRF = 1830MHz
–70
–80
3RF-3LO
fRF = 1806.67MHz
–90
0
–100
–16
–12
–8
–4
5525 G10
5525 G11
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TYPICAL DC PERFOR A CE CHARACTERISTICS
Supply Current vs Supply Voltage
25°C
85°C
–40°C
SHUTDOWN CURRENT (µA)
SUPPLY CURRENT (mA)
30
28
26
24
22
20
18
25°C
85°C
–40°C
16
2.8
3.2
3.6
4
4.4 4.8
SUPPLY VOLTAGE (V)
5.2
5.6
5525 G12
Test circuit shown in Figure 1.
Shutdown Current vs Supply Voltage
20
32
14
4
0
LO INPUT POWER (dBm)
15
10
5
0
2.8
3.2
3.6
4
4.4 4.8
SUPPLY VOLTAGE (V)
5.2
5.6
5525 G13
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LT5525
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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.
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.
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 50Ω 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.
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.
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 55µA for EN = 5V and 0.1µA when EN = 0V.
LO–, LO+ (Pins 14, 15): Differential Inputs for the Local
Oscillator Signal. The LO input is internally matched to
50Ω. 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 480Ω. Thus, a DC
blocking capacitor should be used if the signal source has
a DC voltage present.
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 1µF and 0.01µF capacitors.
Exposed Pad (Pin 17): Circuit Ground Return for the
Entire IC. This must be soldered to the printed circuit board
ground plane.
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 1µF and 0.01µF capacitors.
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BLOCK DIAGRA
17
15
14
LO+
EXPOSED
PAD
LO–
HIGH
SPEED
LO BUFFER
2
3
RF
GND
LINEAR
AMPLIFIER
+
IF+
IF–
RF –
DOUBLEBALANCED
MIXER
GND
12
11
10
9
BIAS
EN
5
VCC2
7
VCC1
6
5525 BD
5525f
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LT5525
TEST CIRCUITS
RF
GND
ER = 4.4
0.018"
LOIN
1760MHz
0.062"
DC
16
C1
OPTIONAL
RFIN
1900MHz
1
17 NC
NC
2
+
RF
15
LO
+
14
LO–
13
NC
GND
IF
LT5525
3
4
GND
NC
900MHz INPUT MATCHING:
C1: 3.9pF
L3
T2
C4
C3
L2
10
6
7
5
2
3
4
IFOUT
140MHz
8
C8
C2
VALUE
SIZE
PART NUMBER
—
0402
Frequency Dependent
C2
0.01µF
0402
AVX 04023C103JAT
C3
1.2pF
0402
AVX 04025A1R2BAT
C4
100pF
0402
AVX 04025A101JAT
C8
1µF
0603
Taiyo Yuden LMK107BJ105MA
T2
1
9
C1
L2, L3
GND
VCC1 VCC2 NC
5
EN
12
+ 11
IF –
RF –
EN
REF DES
0.018"
150nH
1608
4:1
SM-22
5526 F01
VCC
Toko LL1608-FSR15J
M/A-COM ETC4-1-2
Figure 1. Test Schematic
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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 50Ω 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.
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.
5525f
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LT5525
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APPLICATIO S I FOR ATIO
OPTIONAL SERIES
REACTANCE FOR
LOW BAND OR
HIGH BAND
RFIN
MATCHING
3
25
LT5525
RF+
RF–
5525 F02
GAIN AND NF (dB), IIP3 (dBm)
2
20
IIP3
15
SSB NF
10
TA = 25°C
fIF = 140MHz
LOW SIDE LO
HIGH SIDE LO
5
0
GAIN
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
RETURN LOSS (dB)
–5
NO RF
MATCHING
–10
–15
–20
SERIES 1.2nH
–25
SERIES 3.9pF
–30
500
1000
1500
2000
2500
RF FREQUENCY (MHz)
3000
5525 F03
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.
–5
800 850 900 950 1000 1050 1100 1150 1200
RF FREQUENCY (MHz)
5525 F04
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
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APPLICATIO S I FOR ATIO
2
0
LT5525
RF+
RFIN
C5
4.7pF
L3
1.5nH
3
RETURN LOSS (dB)
–5
RF–
–10
–15
5525 F05
Figure 5. Wideband RF Input Matching
–20
0
500
0
2500
1000 1500 2000
FREQUENCY (MHz)
3000
5525 F08
RETURN LOSS (dB)
–5
Figure 8. LO Input Return Loss
NO EXTERNAL
RF MATCHING
–10
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.
–15
–20
SERIES 1.5nH
AND 4.7pF
Table 2. Single-Ended LO Input Impedance
–25
–30
500
1000
3000
1500
2000
2500
RF FREQUENCY (MHz)
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 50Ω. 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
LT5525
LO–
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
20pF
LT5525
VCC
LOIN
50Ω
15
LO+
480Ω
54Ω
IF+
L3
11
T2
4:1
IFOUT
575Ω
20pF
0.7pF
IF–
C3 VCC
L2
10
5525 F07
VCC
5525 F09
Figure 7. LO Input Schematic
Figure 9. IF Output with External Matching
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9
LT5525
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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
574Ω 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 = 200Ω (using a 4:1 transformer for T2 with an external
50Ω load),
n = RIF/RL = 574/200 = 2.87
Q = √(n – 1) = 1.368
XC = RIF/Q = 420Ω
C = 1/(ω • XC) = 2.71pF
C3 = C – CIF = 2.01pF
XL = RL • Q = 274Ω
L2 = L3 = XL/2ω = 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
LT5525
0.7nH
RIF
574Ω
IF+
L3
11
CIF
0.7pF
RL
200Ω
C3
0.7nH
IF–
L2
10
5525 F10
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 50Ω.
RIF • RL
ω
1
C11 = C12 =
ω RIF • RL
L11 = L12 =
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
IFOUT
50Ω
C11
IF–
L12
L13
OPT
C14
VCC
5525 F11
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-
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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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
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
20
19
15
–10
–15
–20
17
250
300
350
400
FREQUENCY (MHz)
450
500
TA = 25°C
fLO = fRF – fIF
fRF = 1900MHz
PLO = –5dBm
PRF = –15dBm
10
5
GAIN
–5
200
250
300
350
400
IF FREQUENCY (MHz)
5525 F12
Figure 12. Typical IF Return Loss
Performance with 240MHz,
360MHz and 450MHz Lumped
Element Baluns
16
15
14
13
0
–25
200
18
IIP3 (dBm)
GAIN (dB), IIP3 (dBm)
RETURN LOSS (dB)
–5
IIP3
450
500
TA = 25°C
12 f = f – f
LO RF IF
11 PLO = –5dBm
PRF = –15dBm
10
1200 1400 1600 1800 2000 2200
RF FREQUENCY (MHz)
5525 F13
Figure 13. Typical Gain and IIP3 vs
IF Frequency with 240MHz,
360MHz and 450MHz Lumped
Element Baluns
240MHz
360MHz
450MHz
2400 2600
5525 F14
Figure 14. Typical IIP3 vs RF
Frequency with Lumped Element
Baluns and IF Frequencies of
240MHz, 360MHz and 450MHz
U
TYPICAL APPLICATIO S
Evaluation Board Layouts
Top Layer Silkscreen
Top Layer Metal
5525f
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.
11
LT5525
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PACKAGE DESCRIPTIO
UF Package
16-Lead Plastic QFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1692)
0.72 ±0.05
R = 0.115
TYP
0.75 ± 0.05
4.00 ± 0.10
(4 SIDES)
0.55 ± 0.20
15
16
PIN 1
TOP MARK
(NOTE 6)
1
4.35 ± 0.05 2.15 ± 0.05
(4 SIDES)
2
2.15 ± 0.10
(4-SIDES)
2.90 ± 0.05
PACKAGE
OUTLINE
(UF) QFN 1103
0.200 REF
0.30 ±0.05
0.65 BSC
0.30 ± 0.05
0.00 – 0.05
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.65 BSC
BOTTOM VIEW—EXPOSED PAD
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
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
RELATED PARTS
PART NUMBER
Infrastructure
LT5512
LT5514
DESCRIPTION
COMMENTS
LT5519
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
LT5520
1.3GHz to 2.3GHz High Linearity Upconverting Mixer
LT5521
3.7GHz Very High Linearity Mixer
LT5522
600MHz to 2.7GHz High Signal Level Downconverting Mixer
LT5526
High Linearity, Low Power Downconverting Mixer
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 50Ω
Matching, Single-Ended LO and RF Ports Operation
15.9dBm IIP3 at 1.9GHz, Integrated RF Output Transformer with 50Ω
Matching, Single-Ended LO and RF Ports Operation
24.2dBm IIP3 at 1.95GHz, 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,
50Ω Single-Ended RF and LO Ports
16.5dBm IIP3 at 900MHz, NF = 11dB, Supply Current = 28mA, 3.6V
to 5.3V Supply
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
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
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12
Linear Technology Corporation
LT/TP 1004 1K • PRINTED IN THE USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2004
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