1
LT5525
5525f
High Linearity, Low Power
Downconverting Mixer
■
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
■
Point-to-Point Data Communication Systems
■
Wireless Infrastructure
■
High Performance Radios
■
High Linearity Receiver Applications
High Signal Level Frequency Downconversion
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
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 infra-
structure systems. The device includes an internally 50Ω
matched high speed LO amplifier driving a double-bal-
anced 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.
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.
IF Output Power and IM3 vs
RF Input Power (Two Input Tones)
RF+
RF–
IF+
IF–
LO–
5525 TA01
LO+
BIAS
EN VCC2
LO INPUT
–5dBm
VCC1
VCC
5V DC
0.01µF
1.2pF
100pF
150nH 4:1
150nH
1900MHz
GND
LT5525
140MHz1900MHz
LNA VGA ADC
RF INPUT POWER (dBm/TONE)
–20
–100
OUTPUT POWER (dBm/TONE)
–90
–70
–60
–50
0
–30
–15 –10
5525 TA02
–80
–20
P
OUT
IM3
–10
–40
–5 0
T
A
= 25°C
f
RF
= 1900MHz
f
LO
= 1760MHz
f
IF
= 140MHz
P
LO
= –5dBm
, 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.
2
LT5525
5525f
ORDER PART
NUMBER
(Note 1)
Supply Voltage ...................................................... 5.5V
Enable Voltage ............................... –0.3V to V
CC
+ 0.3V
LO Input Power ............................................... +10dBm
LO
+
to LO
–
Differential DC Voltage ......................... ±1V
LO
+
and LO
–
Common Mode DC Voltage... –0.5V to V
CC
RF Input Power ................................................ +10dBm
RF
+
to RF
–
Differential DC Voltage ..................... ±0.13V
RF
+
and RF
–
Common Mode DC Voltage ... –0.5V to V
CC
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 (T
J
)................................... 125°C
LT5525EUF
T
JMAX
= 125°C, θ
JA
= 37°C/W
EXPOSED PAD (PIN 17) IS GND,
MUST BE SOLDERED TO PCB.
NC PINS SHOULD BE GROUNDED
ABSOLUTE MAXIMUM RATINGS
W
WW
U
PACKAGE/ORDER INFORMATION
W
UU
VCC = 5V, EN = 3V, TA = 25°C (Note 3), unless otherwise noted. Test circuit shown in Figure 1.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
16 15 14 13
5678
TOP VIEW
17
UF PACKAGE
16-LEAD (4mm × 4mm) PLASTIC QFN
9
10
11
12
4
3
2
1NC
RF
+
RF
–
NC
GND
IF
+
IF
–
GND
NC
LO
+
LO
–
NC
EN
V
CC1
V
CC2
NC
UF PART
MARKING
5525
DC ELECTRICAL CHARACTERISTICS
AC ELECTRICAL CHARACTERISTICS
(Notes 2, 3)
PARAMETER CONDITIONS MIN TYP MAX UNITS
RF Input Frequency Range (Note 4) Requires RF Matching Below 1300MHz 800 to 2500 MHz
LO Input Frequency Range (Note 4) 500 to 3000 MHz
IF Output Frequency Range (Note 4) Requires IF Matching 0.1 to 1000 MHz
VCC = 5V, EN = 3V, TA = 25°C. Test circuit shown in Figure 1. (Notes 2, 3)
PARAMETER CONDITIONS MIN TYP MAX UNITS
RF Input Return Loss Z
O
= 50Ω15 dB
LO Input Return Loss Z
O
= 50Ω, External DC Blocks 15 dB
IF Output Return Loss Z
O
= 50Ω, External Match 15 dB
LO Input Power –10 to 0 dBm
PARAMETER CONDITIONS MIN TYP MAX UNITS
Power Supply Requirements (V
CC
)
Supply Voltage (Note 6) 3.6 5 5.3 V
Supply Current V
CC
= 5V 28 33 mA
Shutdown Current EN = Low 100 µA
Enable (EN) Low = Off, High = On
EN Input High Voltage (On) 3V
EN Input Low Voltage (Off) 0.3 V
Enable Pin Input Current EN = 5V 55 µA
EN = 0V 0.1 µA
Turn-On Time (Note 5) 3µs
Turn-Off Time (Note 5) 6µs
3
LT5525
5525f
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 MIN TYP MAX UNITS
Conversion Gain f
RF
= 900MHz –2.6 dB
f
RF
= 1900MHz –1.9 dB
f
RF
= 2100MHz –2.0 dB
f
RF
= 2500MHz –2.0 dB
Conversion Gain vs Temperature T
A
= –40°C to 85°C –0.020 dB/°C
Input 3rd Order Intercept f
RF
= 900MHz 21.0 dBm
f
RF
= 1900MHz 17.6 dBm
f
RF
= 2100MHz 17.6 dBm
f
RF
= 2500MHz 12.0 dBm
Single Sideband Noise Figure f
RF
= 900MHz 14.0 dB
f
RF
= 1900MHz 15.1 dB
f
RF
= 2100MHz 15.6 dB
f
RF
= 2500MHz 15.6 dB
LO to RF Leakage f
LO
= 500MHz to 1000MHz ≤–50 dBm
f
LO
= 1000MHz to 3000MHz ≤–43 dBm
LO to IF Leakage f
LO
= 500MHz to 1400MHz ≤–50 dBm
f
LO
= 1400MHz to 3000MHz ≤–39 dBm
RF to LO Isolation f
RF
= 500MHz to 3000MHz >38 dB
RF to IF Isolation f
RF
= 900MHz 62 dB
f
RF
= 1900MHz 42 dB
f
RF
= 2100MHz 40 dB
f
RF
= 2500MHz 33 dB
Input 1dB Compression f
RF
= 900MHz 7.6 dBm
f
RF
= 1900MHz 4 dBm
f
RF
= 2100MHz 4 dBm
f
RF
= 2500MHz 3 dBm
2RF-2LO Output Spurious Product 900MHz: f
RF
= 830MHz at –15dBm –63 dBc
(f
RF
= f
LO
+ f
IF
/2) 1900MHz: f
RF
= 1830MHz at –15dBm –53 dBc
2100MHz: f
RF
= 2030MHz at –15dBm –45 dBc
2500MHz: f
RF
= 2430Hz at –15dBm –42 dBc
3RF-3LO Output Spurious Product 900MHz: f
RF
= 806.67MHz at –15dBm –74 dBc
(f
RF
= f
LO
+ f
IF
/3) 1900MHz: f
RF
= 1806.67MHz at –15dBm –59 dBc
2100MHz: f
RF
= 2006.67MHz at –15dBm –59 dBc
2500MHz: f
RF
= 2406.67Hz at –15dBm –60 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.
4
LT5525
5525f
WU
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 LO Input Power
Conversion Gain and IIP3
vs Supply Voltage
SSB Noise Figure
vs LO Input Power
RF, LO and IF Port Return Loss
vs Frequency
SSB NF vs RF Frequency
IF Output Power and IM3 vs RF
Input Power (Two Input Tones)
LO-IF, LO-RF and RF-LO Leakage
vs Frequency
Conversion Gain and IIP3
vs RF Frequency (High Side LO)
RF FREQUENCY (MHz)
900
–5
GAIN (dB), IIP3 (dBm)
0
5
10
15
1300 1700 2100 2500
5525 G01
20 IIP3
GAIN
25
1100 1500 1900 2300
25°C
85°C
–40°C
RF FREQUENCY (MHz)
900
–5
GAIN (dB), IIP3 (dBm)
0
5
10
15
1300 1700 2100 2500
5525 G02
20
IIP3
GAIN
25
1100 1500 1900 2300
25°C
85°C
–40°C
RF FREQUENCY (MHz)
900
12
NOISE FIGURE (dB)
11
13
14
15
20
17
1300 1700 1900
5525 G03
12
18
19
16
1100 1500 2100 2300 2500
HIGH SIDE LO
LOW SIDE LO
LO INPUT POWER (dBm)
–5
GAIN (dB), IIP3 (dBm)
5
15
25
0
10
20
–12 –8 –4 0
5525 G04
4–14–16 –10 –6 –2 2
25°C
85°C
–40°C
IIP3
GAIN
LO INPUT POWER (dBm)
–14
NOISE FIGURE (dB)
16
18
2
5525 G05
14
12 –10 –6 –2
–12 –8 –4 0
20
15
17
13
19
25°C
85°C
–40°C
FREQUENCY (MHz)
500
LEAKAGE (dBm)
–40
–20
0
2500
5525 G06
–60
–80
–50 LO-RF
LO-IF
–30
–10
–70
–90
–100 1000 1500 2000 3000
RF-LO
SUPPLY VOLTAGE (V)
2.8
GAIN (dB), IIP3 (dBm)
15
20
25
4 4.8
5525 G07
10
IIP3
GAIN
5
3.2 3.6 4.4 5.2 5.6
0
–5
25°C
85°C
–40°C
FREQUENCY (MHz)
0
–30
RETURN LOSS (dB)
–25
–20
–15
–10
0
500
IF
LO
RF
1000 1500 2000
5525 G08
2500 3000
–5
RF INPUT POWER (dBm/TONE)
–20
–100
OUTPUT POWER (dBm/TONE)
–90
–70
–60
–50
0
–30 POUT
IM3
–15 –10
5525 G09
–80
–20
–10
–40
–5 0
25°C
85°C
–40°C
5
LT5525
5525f
WU
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
WU
TYPICAL DC PERFOR A CE CHARACTERISTICS
Supply Current vs Supply Voltage Shutdown Current vs Supply Voltage
Test circuit shown in Figure 1.
RF INPUT POWER (dBm)
–20
–100
OUTPUT POWER (dBm)
–80
–60
–40
–20
–15 –5–10
5525 G10
0
0
–90
–70
–50
–30
–10
10
IF OUT
f
RF
= 1900MHz
3RF-3LO
f
RF
= 1806.67MHz
T
A
= 25°C
f
LO
= 1760MHz
f
IF
= 140MHz
2RF-2LO
f
RF
= 1830MHz
LO INPUT POWER (dBm)
–16
–50
–40
–30
0
5525 G11
–60
–70
–12 –8 –4 4
–80
–90
–100
OUTPUT POWER (dBm)
3RF-3LO
f
RF
= 1806.67MHz
T
A
= 25°C
f
LO
= 1760MHz
f
IF
= 140MHz
2RF-2LO
f
RF
= 1830MHz
SUPPLY VOLTAGE (V)
2.8
14
SUPPLY CURRENT (mA)
16
20
22
24
4.4
32
5525 G12
18
3.6
3.2 4.8 5.2
4 5.6
26
28
30
25°C
85°C
–40°C
SUPPLY VOLTAGE (V)
2.8
0
SHUTDOWN CURRENT (µA)
5
10
15
20
3.2 3.6 4 4.4
5525 G13
4.8 5.2 5.6
25°C
85°C
–40°C
6
LT5525
5525f
UU
U
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 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.
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.
V
CC1
(Pin 6): Power Supply Pin for the LO Buffer Circuits.
Typical current consumption is 11mA. This pin should be
externally connected to the other V
CC
pins and decoupled
with 1µF and 0.01µF capacitors.
V
CC2
(Pin 7): Power Supply Pin for the Bias Circuits.
Typical current consumption is 2.5mA. This pin should be
externally connected to the other V
CC
pins and decoupled
with 1µF and 0.01µF 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 V
CC
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
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.
Exposed Pad (Pin 17): Circuit Ground Return for the
Entire IC. This must be soldered to the printed circuit board
ground plane.
BLOCK DIAGRA
W
15 14
6
11
2
3
75
10
HIGH
SPEED
LO BUFFER
DOUBLE-
BALANCED
MIXER
LINEAR
AMPLIFIER
LO–
EXPOSED
PAD
LO+
VCC2 VCC1
EN
IF+
12
17
GND
IF–
9
GND
5525 BD
BIAS
RF+
RF–
7
LT5525
5525f
TEST CIRCUITS
REF DES VALUE SIZE PART NUMBER
C1 — 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
L2, L3 150nH 1608 Toko LL1608-FSR15J
T2 4:1 SM-22 M/A-COM ETC4-1-2
Figure 1. Test Schematic
IFOUT
140MHz
5526 F01
16 15 14 13
56 78
12
11
10
9
NC NC
GND
GND
EN
EN
VCC1 VCC2
RF+
RF–
LO+LO–
NC
17
1
2
3
4NC
NC
IF+
IF–
RFIN
1900MHz
LOIN
1760MHz
15
4
3
2
C4
L3
L2
C3
C2 C8
VCC
LT5525
RF
GND
GND
DC
ER = 4.4
0.018"
0.018"
0.062"
900MHz INPUT MATCHING:
C1: 3.9pF
C1
OPTIONAL T2
APPLICATIO S I FOR ATIO
WUUU
T
he 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 single-
ended 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 second-
ary 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 pri-
mary winding of the balun.
8
LT5525
5525f
APPLICATIO S I FOR ATIO
WUUU
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.
2
OPTIONAL SERIES
REACTANCE FOR
LOW BAND OR
HIGH BAND
MATCHING
RF+
RFIN
LT5525
5525 F02
3RF–
Figure 2. RF Input Schematic
RF FREQUENCY (MHz)
500
–30
RETURN LOSS (dB)
–25
–20
–15
–10
–5
0
1000 1500 2000 2500
5525 F03
3000
NO RF
MATCHING
SERIES 1.2nH
SERIES 3.9pF
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) ver-
sus 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 simu-
late board-level interfacing to an input filter, or to design
a broadband input matching network.
Table 1. RF Port Input Impedance vs Frequency
FREQUENCY INPUT REFLECTION COEFFICIENT
(MHz) IMPEDANCE MAG ANGLE
50 10.4 + j2.63 0.675 174
500 18.1 + j23.7 0.551 124
700 25.8 + j30.7 0.478 106
900 36.5 + j34.5 0.398 90
1100 48.4 + j33.3 0.321 74
1300 59.5 + j25.7 0.244 57
1500 65.9 + j13.1 0.177 33
1700 65.0 – j1.0 0.131 –3
1900 59.0 – j12.2 0.138 –47
2100 50.2 – j19.0 0.187 –79
2300 41.8 – j22.1 0.250 –97
2500 34.9 – j22.7 0.311 –109
2700 29.1 – j21.9 0.369 –118
3000 23.2 – j19.1 0.435 –130
RF FREQUENCY (MHz)
800
–5
GAIN AND NF (dB), IIP3 (dBm)
0
5
10
15
900 1000 1100 1200
5525 F04
IIP3
25
20
850 950 1050 1150
LOW SIDE LO
HIGH SIDE LO
SSB NF
GAIN
TA = 25°C
fIF = 140MHz
Figure 4. Typical Gain, IIP3 and NF with
Series 3.9pF Matching Capacitor
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 broad-
band 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
9
LT5525
5525f
APPLICATIO S I FOR ATIO
WUUU
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.
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 INPUT REFLECTION COEFFICIENT
(MHz) IMPEDANCE MAG ANGLE
100 93.1 – j121 0.686 –30
250 55.8 – j54 0.457 –57
500 47.7 – j28 0.276 –79
1000 42.3 – j14 0.171 –110
1500 38.5 – j9.3 0.166 –135
2000 35.8 – j7.8 0.187 –146
2500 34.8 – j7.8 0.281 –148
3000 34.2 – j8.7 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 con-
nected 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
Figure 7. LO Input Schematic
Figure 9. IF Output with External Matching
Figure 8. LO Input Return Loss
Figure 5. Wideband RF Input Matching
Figure 6. RF Input Return Loss Using
Wideband Matching Network
2RF
+
RF
IN
L3
1.5nH
C5
4.7pF
LT5525
5525 F05
3RF
–
RF FREQUENCY (MHz)
500
–30
RETURN LOSS (dB)
–25
–20
–15
–10
–5
0
1000 1500 2000 2500
5525 F06
3000
SERIES 1.5nH
AND 4.7pF
NO EXTERNAL
RF MATCHING
14 LO
–
480Ω
20pF
20pF
LO
IN
50Ω
LT5525
5525 F07
15 LO
+
V
CC
54Ω
FREQUENCY (MHz)
0
–20
RETURN LOSS (dB)
–15
–10
–5
0
500 1000 1500 2000
5525 F08
2500 3000
10
11
575Ω
C3
5525 F09
V
CC
L3 IF
OUT
T2
4:1
L2
V
CC
0.7pF
LT5525
IF
–
IF
+
10
LT5525
5525f
APPLICATIO S I FOR ATIO
WUUU
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 (R
IF
) 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 imped-
ance 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
R
L
= 200Ω (using a 4:1 transformer for T2 with an external
50Ω load),
n = R
IF
/R
L
= 574/200 = 2.87
Q = √(n – 1) = 1.368
X
C
= R
IF
/Q = 420Ω
C = 1/(ω • X
C
) = 2.71pF
C3 = C – C
IF
= 2.01pF
X
L
= R
L
• Q = 274Ω
L2 = L3 = X
L
/2ω = 156nH
Table 3. IF Differential Impedance (Parallel Equivalent)
FREQUENCY OUTPUT REFLECTION COEFFICIENT
(MHz) IMPEDANCE MAG ANGLE
70 575|| – j3.39k 0.840 –1.8
140 574|| – j1.67k 0.840 –3.5
240 572|| – j977 0.840 –5.9
450 561|| – j519 0.838 –11.1
750 537|| – j309 0.834 –18.6
860 525|| – j267 0.831 –21.3
1000 509|| – j229 0.829 –24.8
1250 474|| – j181 0.822 –31.3
1500 435|| – j147 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-
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 resis-
tance, R
L
, is 50Ω.
LL RR
CC RR
IF L
IF L
11 12
11 12 1
==
==
•
•
ω
ω
I
nductor 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 wire-
wound inductor. Capacitor C13 is a DC block which can
also be used to adjust the impedance match. Capacitor
C14 is a bypass capacitor.
Figure 10. IF Output Small Signal Model
10
11
RIF
574Ω
5525 F10
0.7nH L3
L2
0.7nH
CIF
0.7pF
LT5525
IF–
IF+
RL
200Ω
C3
Figure 11. Narrowband Bridge IF Balun
IF
+
C12
IF
OUT
50Ω
L12
L11
C11
IF
–
V
CC
C13
C14
L14
OPT
L13
OPT
5525 F11
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.
11
LT5525
5525f
APPLICATIO S I FOR ATIO
WUUU
TYPICAL APPLICATIO S
U
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 represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
Conversion gain and IIP3 performance with an RF fre-
quency 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.
Table 4. Component Values for Lumped Balun
IF FREQ (MHz) L11, L12 (nH) C11, C12 (pF) C13 (pF) L14 (nH)
240 100 3.9 100 560
360 68 2.7 10 270
450 56 2.2 8.2 180
Figure 12. Typical IF Return Loss
Performance with 240MHz,
360MHz and 450MHz Lumped
Element Baluns
FREQUENCY (MHz)
200
–25
RETURN LOSS (dB)
–20
–15
–10
–5
0
250 300 350 400
5525 F12
450 500
IF FREQUENCY (MHz)
200
–5
GAIN (dB), IIP3 (dBm)
0
5
10
15
20
IIP3
GAIN
250 300 350 400
5525 F13
450 500
TA = 25°C
fLO = fRF – fIF
fRF = 1900MHz
PLO = –5dBm
PRF = –15dBm
RF FREQUENCY (MHz)
1200
10
IIP3 (dBm)
11
13
14
15
20
17
1600 2000 2200
5525 F14
12
18
19
16
1400 1800 2400 2600
240MHz
360MHz
450MHz
TA = 25°C
fLO = fRF – fIF
PLO = –5dBm
PRF = –15dBm
Figure 13. Typical Gain and IIP3 vs
IF Frequency with 240MHz,
360MHz and 450MHz Lumped
Element Baluns
Figure 14. Typical IIP3 vs RF
Frequency with Lumped Element
Baluns and IF Frequencies of
240MHz, 360MHz and 450MHz
12
LT5525
5525f
© LINEAR TECHNOLOGY CORPORATION 2004
LT/TP 1004 1K • PRINTED IN THE USA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
UF Package
16-Lead Plastic QFN (4mm × 4mm)
(Reference LTC DWG # 05-08-1692)
U
PACKAGE DESCRIPTIO
4.00 ± 0.10
(4 SIDES)
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
PIN 1
TOP MARK
(NOTE 6)
0.55 ± 0.20
1615
1
2
BOTTOM VIEW—EXPOSED PAD
2.15 ± 0.10
(4-SIDES)
0.75 ± 0.05 R = 0.115
TYP
0.30 ± 0.05
0.65 BSC
0.200 REF
0.00 – 0.05
(UF) QFN 1103
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
0.72 ±0.05
0.30 ±0.05
0.65 BSC
2.15 ± 0.05
(4 SIDES)
2.90 ± 0.05
4.35 ± 0.05
PACKAGE
OUTLINE
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 DESCRIPTION COMMENTS
Infrastructure
LT5512 DC-3GHz High Signal Level Down Converting Mixer 21dBm IIP3, Integrated LO Buffer
LT5514 Ultralow Distortion, IF Amplifier/ADC Driver with Digitally 850MHz Bandwidth, 47dBm OIP3 at 100MHz, 10.5dB to 33dB Gain
Controlled Gain Control Range
LT5519 0.7GHz to 1.4GHz High Linearity Upconverting Mixer 17.1dBm IIP3 at 1GHz, Integrated RF Output Transformer with 50Ω
Matching, Single-Ended LO and RF Ports Operation
LT5520 1.3GHz to 2.3GHz High Linearity Upconverting Mixer 15.9dBm IIP3 at 1.9GHz, Integrated RF Output Transformer with 50Ω
Matching, Single-Ended LO and RF Ports Operation
LT5521 3.7GHz Very High Linearity Mixer 24.2dBm IIP3 at 1.95GHz, 12.5dB SSBNF, –42dBm LO Leakage,
Supply Voltage = 3.15V to 5.25V
LT5522 600MHz to 2.7GHz High Signal Level Downconverting Mixer 4.5V to 5.25V Supply, 25dBm IIP3 at 900MHz, NF = 12.5dB,
50Ω Single-Ended RF and LO Ports
LT5526 High Linearity, Low Power Downconverting Mixer 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 44dB Dynamic Range, Temperature Compensated, SC70 Package
LTC5532 300MHz to 7GHz Precision RF Power Detector Precision V
OUT
Offset Control, Adjustable Gain and Offset
LT5534 50MHz to 3GHz RF Power Detector with 60dB Dynamic Range ±1dB Output Variation over Temperature, 38ns Response Time
LTC5535 600MHz to 7GHz RF Power Detector 12MHz Baseband BW, Precision Offset with Adjustable Gain and Offset
Wide Bandwidth ADCs
LTC1749 12-Bit, 80Msps ADC 500MHz BW S/H, 71.8dB SNR, 87dB SFDR
LTC1750 14-Bit, 80Msps ADC 500MHz BW S/H, 75.5dB SNR, 90dB SFDR, 2.25V
P-P
or 1.35V
P-P
Input Ranges
LTC2222/ 12-Bit, 105Msps/80Msps ADC Low Power 775MHz BW S/H, 61dB SNR, 75dB SFDR ±0.5V or ±1V
LTC2223 Input
LTC2224/ 10-Bit/12-Bit, 135Msps ADC Low Power 775MHz BW S/H, 61dB SNR, 75dB SFDR ±0.5V or ±1V
LTC2234 Input
