LT5546
40MHz to 500MHz VGA
and I/Q Demodulator with
17MHz Baseband Bandwidth
FEATURES
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DESCRIPTIO
17MHz I/Q Lowpass Output Noise Filters
Wide Range 1.8V to 5.25V Supply Voltage
Frequency Range: 40MHz to 500MHz
THD < 0.14% (–57dBc)
at 800mV
P-P
Differential Output Level
IF Overload Detector
Log Linear Gain Control Range: –7dB to 56dB
Baseband I/Q Amplitude Imbalance: 0.2dB
Baseband I/Q Phase Imbalance: 0.6°
7.8dB Noise Figure at Max Gain
Input IP3 at Low Gain: – 1dBm
Low Supply Current: 24mA
Low Delay Shift Over Gain Control Range: 2ps/dB
Outputs Biased Up While in Standby
16-Lead QFN 4mm
×
4mm Package with Exposed Pad
APPLICATIO S
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GPS IF Receivers
Satellite IF Receivers
VHF/UHF Receivers
Wireless Local Loop
The LT
®
5546 is a 40MHz to 500MHz monolithic integrated
quadrature demodulator with variable gain amplifier (VGA)
and 17MHz I/Q baseband bandwidth designed for low volt-
age operation. It supports standards that use a linear modu-
lation format. The chip consists of a VGA, quadrature down-
converting mixers and 17MHz lowpass noise filters (LPF).
The LO port consists of a divide-by-two stage and LO
buffers. The IC provides all building blocks for IF down-
conversion to I and Q baseband signals with a single
supply voltage of 1.8V to 5.25V. The VGA gain has a linear-
in-dB relationship to the control input voltage. Hard-clip-
ping amplifiers at the mixer outputs reduce the recovery
time from a signal overload condition. The lowpass filters
reduce the out-of-band noise and spurious frequency
components. The –3dB corner frequency of the noise
filters is approximately 17MHz and has a first order roll-
off. The standby mode provides reduced supply current
and fast transient response into the normal operating mode
when the I/Q outputs are AC-coupled to a baseband chip.
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
280MHz
IF INPUT
L1
15nH
C3
10pF
L2
15nH
IF
+
C2
1µF
C1
1nF
V
CC
1.8V
–25
–30
I
OUT
+
IF
–
–35
THD (dBc)
I
OUT
–
–40
–45
–50
–55
–60
–60
GAIN CONTROL
2xLO
C4
560MHz
3.3pF
INPUT
V
CTRL
2xLO
+
L3
39nH
2xLO
–
EN
STBY
GND
÷2
IF DET
Q
OUT
+
C3
1.8pF
Q
OUT–
LT5546
5546 TA01
C5
3.3pF
ENABLE STANDBY
U
Total Harmonic Distortion vs
IF Input Level at 1.8V Supply
f
IF, 1
= 280MHz
f
IF, 2
= 280.1MHz
f
2xLO
= 570MHz
800mV
P-P
DIFFERENTIAL OUT
–40
–30
–20
–50
IF INPUT POWER EACH TONE (dBm)
–10
5546 TA01b
U
U
5546fa
1
LT5546
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
Q
OUT+
Q
OUT–
I
OUT+
I
OUT–
Supply Voltage ....................................................... 5.5V
Differential Voltage Between 2xLO
+
and 2xLO
–
.......... 4V
IF
+
, IF
–
............................................. –500mV to 500mV
I
OUT+
, I
OUT–
, Q
OUT+
, Q
OUT–
.................. V
CC
– 1.8V to V
CC
Operating Ambient Temperature
(Note 2) ...................................................–40°C to 85°C
Storage Temperature Range ..................–65°C to 125°C
Voltage on Any Pin
Not to Exceed ........................ –500mV to V
CC
+ 500mV
ORDER PART
NUMBER
12 STBY
16 15 14 13
GND 1
IF
IF
+
–
LT5546EUF
2
3
17
11 2xLO
+
10 2xLO
–
9
EN
GND 4
5
V
CC
6
V
CTRL
7
IF DET
8
V
CC
UF PART MARKING
5546
UF PACKAGE
16-LEAD (4mm
×
4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 37°C/W
EXPOSED PAD IS GND (PIN 17)
(MUST BE SOLDERED TO PCB)
Consult LTC Marketing for parts specified with wider operating temperature ranges.
V
CC
= 3V, f
2xLO
= 570MHz, P
2xLO
= –5dBm (Note 5), f
IF
= 284MHz,
P
IF
= –30dBm, I and Q outputs 800mV
P-P
into 4kΩ differential load, T
A
= 25°C, EN = V
CC
, STBY = V
CC
, unless otherwise noted. (Note 3)
SYMBOL
IF Input
f
IF
Frequency Range
Nominal Input Level
Input Impedance
NF
G
L
G
H
IIP3
IIP2
Noise Figure at Max Gain
Min Gain (Note 4)
Max Gain (Note 4)
Input IP3, Min Gain
Input IP3, Max Gain
Input IP2, Min Gain
Input IP2, Max Gain
Nominal Voltage Swing
Clipping Level
DC Common Mode Voltage
I/Q Amplitude Imbalance
I/Q Phase Imbalance
DC Offset
Output Driving Capability
r
o
Small-Signal Output Impedance
STBY to Turn-On Delay
I/Q Output 1dB Compression
I/Q Output IM3
P
IF, 1
= –25.5dBm, 280MHz
P
IF, 2
= –25.5dBm, 280.1MHz (Note 7)
(Note 8)
(Note 8)
(Notes 6, 8)
Single Ended, C
LOAD
≤
10pF
(Note 6)
2
R
SOURCE
= 200Ω Differential
IF
+
, IF
–
to GND, EN = V
CC
IF
+
, IF
–
to GND, EN = GND
V
CTRL
= 1.7V
V
CTRL
= 0.2V
V
CTRL
= 1.7V
P
IF
= –22.5dBm (Note 7)
P
IF
= –75dBm (Note 7)
V
CTRL
= 0.2V (Note 9)
V
CTRL
= 1.7V (Note 9)
(Note 6)
(Note 6)
49
40 to 500
–76 to –19
100Ω//1.2pF
1pF
7.8
1.6
56
–1
–49
36
–25
0.8
1.47
V
CC
– 1.19
0.14
0.6
21
1.5
180
0.3
–10
– 49
0.6
3
6
dB
dB
dB
dBm
dBm
dBm
dBm
V
P-P
V
P-P
V
dB
Deg
mV
kΩ
Ω
µs
dBm
dBc
5546fa
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
MHz
dBm
Demodulator I/Q Output
2
U
W
U
U
W W
W
LT5546
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
Gain Slope Linearity Error
Temperature Gain Shift
Gain Control Response Time
Gain Control Voltage Range
Gain Control Slope
Gain Control Input Impedance
Delay Shift Over Gain Control
Baseband Lowpass Filter (LPF)
–3dB Cutoff Frequency
Amplitude Roll-Off at 50MHz
Group Delay Ripple
2xLO Input
f
2xLO
P
2xLO
Frequency Range
Input Power
Input Power
Input Impedance
DC Common Mode Voltage
IF Detector
IF Detector Range
Output Voltage Range
Detector Response Time
Power Supply
V
CC
I
CC
I
OFF
I
STBY
Mode
Enable
Disable
Standby
No Standby
Enable Pin Voltage
Enable Pin Voltage
Standby Pin Voltage
Standby Pin Voltage
EN = High
EN = Low
STBY = High
STBY = Low
1
0.5
1
0.5
V
V
V
V
Supply Voltage
Supply Current
Shutdown Current
Standby Current
EN = High, STBY = Low or High
EN, STBY < 350mV
EN = Low; STBY = High
1.8
24
0.2
3.6
5.25
34
30
6
V
mA
µA
mA
Referred to IF Input
For P
IF
= –30dBm to 8dBm
With External 1.8pF Load,
Settling within 10% of Final Value
–30 to 8
0.27 to 1.2
80
dBm
V
ns
1:2 Transformer with 240Ω Shunt Resistor (Note 5)
LC Balun (Note 5)
Differential Between 2xLO
+
and 2xLO
–
–20
80 to 1000
–5
–10
800Ω//0.4pF
V
CC
– 0.4
V
MHz
dBm
dBm
13
17
–9
1
MHz
dB
ns
To Internal 0.2V Reference
Measured Over 10dB Step
Variable Gain Amplifier (VGA)
V
CTRL
= 0V to 1.4V
T = –40°C to 85°C, V
CTRL
= 0V to 1.4V
Settled within 10% of Final Value
±0.5
±0.4
90
0 to 1.7
41
25
2
dB
dB
ns
V
dB/V
kΩ
ps/dB
V
CC
= 3V, f
2×LO
= 570MHz, P
2×LO
= –5dBm (Note 5), f
IF
= 284MHz,
P
IF
= –30dBm, I and Q outputs 800mV
P-P
into 4kΩ differential load, T
A
= 25°C, EN = V
CC
, STBY = V
CC
, unless otherwise noted. (Note 3)
CONDITIONS
MIN
TYP
MAX
UNITS
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
Specifications over the –40°C to 85°C temperature range are
assured by design, characterization and correlation with statistical process
controls.
Note 3:
Tests are performed as shown in the configuration of Figure 6. The
IF input transformer loss is substracted from the measured values.
Note 4:
Power gain is defined here as the I (or Q) output power into a 4kΩ
differential load, divided by the IF input power in dB. To calculate the
voltage gain between the differential I output (or Q output) and the IF
input, including ideal matching network, 10 • log(4kΩ/50) = 19dB has to
be added to this power gain.
Note 5:
If a narrow-band match is used in the 2xLO path instead of a 1:2
transformer with 240Ω shunt resistor, 2xLO input power can be reduced
to –10dBm, without degrading the phase imbalance. See Figure 11 and
Figure 6.
Note 6:
Differential between I
OUT+
and I
OUT–
(or differential between
Q
OUT+
and Q
OUT–
).
Note 7:
The gain control voltage V
CTRL
is set in such a way that the
differential output voltage between I
OUT+
and I
OUT–
(or differential between
Q
OUT+
and Q
OUT–
) is 800mV
P-P
, with the given input power P
IF
. IF
frequencies are 280MHz and 280.1MHz, with f
2xLO
= 570MHz.
Note 8:
The typical parameter is defined as the mean of the absolute
values of the data distribution.
Note 9:
IF frequency is 125MHz, with f
2xLO
= 502MHz.
5546fa
3
LT5546
V
CC
= 3V, f
2×LO
= 570MHz, P
2×LO
= –5dBm
(Note 5), f
IF
= 284MHz, P
IF
= –30dBm, I and Q outputs 800mV
P-P
into 4kΩ differential load, T
A
= 25°C, EN = V
CC
, STBY = V
CC
,
unless otherwise noted. (Note 3)
Gain and Noise Figure
Supply Current vs Supply Voltage
vs Control Voltage at 3V Supply
28
85°C
TYPICAL PERFOR A CE CHARACTERISTICS
SUPPLY CURRENT (mA)
26
25°C
24
–40°C
22
GAIN AND NOISE FIGURE (dB)
20
1.75 2.25 2.75 3.25 3.75 4.25 4.75 5.25
SUPPLY VOLTAGE (V)
5546 G01
Gain and Noise Figure
vs Control Voltage at 1.8V Supply
60
GAIN DEVIATI0N FROM LINEAR FIT (dB)
50
GAIN AND NOISE FIGURE (dB)
40
30
20
NF
10
GAIN
0
–10
0
0.3
0.6
0.9
V
CTRL
(V)
5546 G03
Gain and Noise Figure
vs Control Voltage and V
CC
60
50
GAIN AND NOISE FIGURE (dB)
60
50
GAIN AND NOISE FIGURE (dB)
40
30
20
NF
10
GAIN
0
–10
0
0.3
0.6
0.9
V
CTRL
(V)
5546 G05
4
U W
1.2
1.2
60
50
40
30
20
NF
10
GAIN
0
–10
0
0.3
0.6
0.9
V
CTRL
(V)
5546 G02
f
IF
= 284MHz
f
2xLO
= 570MHz
1.2
1.5
1.8
GAIN AT 25°C
NF AT 25°C
GAIN AT –40°C
NF AT –40°C
GAIN AT 85°C
NF AT 85°C
Gain Flatness
vs Control Voltage at 3V Supply
0.5
0.4
0.3
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
–0.5
0
0.3
0.9
0.6
V
CTRL
(V)
1.2
1.5
5546 G04
–40°C
85°C
f
IF
= 284MHz
f
2xLO
= 570MHz
1.5
1.8
GAIN AT –40°C
NF AT 25°C
GAIN AT 25°C
NF AT –40°C
GAIN AT 85°C
NF AT 85°C
25°C
Gain and Noise Figure
vs IF Frequency at 3V Supply
GAIN, V
CTRL
= 1.6V
NF, V
CTRL
= 0.2V
40
GAIN, V
CTRL
= 0.9V
30
20
10
0
–10
10
100
IF FREQUENCY (MHz)
1000
5546 G06
NF, V
CTRL
= 0.9V
NF, V
CTRL
= 1.6V
f
IF
= 284MHz
f
2xLO
= 570MHz
1.5
1.8
GAIN AT 1.8V
NF AT 1.8V
GAIN AT 3V
NF AT 3V
GAIN AT 5.25V
NF AT 5.25V
GAIN, V
CTRL
= 0.2V
5546fa
LT5546
V
CC
= 3V, f
2×LO
= 570MHz, P
2×LO
= –5dBm
(Note 5), f
IF
= 284MHz, P
IF
= –30dBm, I and Q outputs 800mV
P-P
into 4kΩ differential load, T
A
= 25°C, EN = V
CC
, STBY = V
CC
,
unless otherwise noted. (Note 3)
Total Harmonic Distortion
vs IF Input Power at 3V Supply
and 800mV
P-P
Differential Out
–25
–30
–35
THD (dBc)
THD (dBc)
TYPICAL PERFOR A CE CHARACTERISTICS
Total Harmonic Distortion
vs IF Input Power and IF
Frequency
–25
–30
–35
–40
–45
–50
–55
–60
–60
f
IF
= 40MHz
800mV
P-P
DIFFERENTIAL OUT
3V SUPPLY
f
IF,1
= 280MHz
f
IF,2
= 280.1MHz
f
2xLO
= 570MHz
–40
25°C
–45
–40°C
–50
–55
–60
–60
85°C
THD (dBc)
–20
–30
IF INPUT POWER EACH TONE (dBm)
–50
–40
Total Harmonic Distortion vs IF
Input Power and Supply Voltage
800mV
P-P
DIFFERENTIAL OUT
f
IF,1
= 280MHz
–30 f
IF,2
= 280.1MHz
f
2xLO
= 570MHz
–35
THD (dBc)
–25
–35
MAGNITUDE (dB)
–40
–45
–50
1.8V
–55
–60
–60
–50
THD (dBc)
3V
5.25V
–20
–30
IF INPUT POWER EACH TONE (dBm)
–40
LPF Frequency Response
vs Baseband Frequency and
Supply Voltage
0
–1
–2
MAGNITUDE (dB)
–3
–4
–5
3V
–6
–7
–8
–9
–10
0
5.25V
1.8V
IF DET OUTPUT (V)
IF DET OUTPUT (V)
5 10 15 20 25 30 35 40 45 50 55
BASEBAND FREQUENCY (MHz)
5546 G13
U W
5546 G07
5546 G10
Total Harmonic Distortion
vs IF Input Power at 1.8V Supply
and 800mV
P-P
Differential Out
–25
–30
–35
–40
–45
–50
f
IF,1
= 280MHz
f
IF,2
= 280.1MHz
f
2xLO
= 570MHz
25°C
–40°C
85°C
f
IF
= 280MHz
–55
f
IF
= 500MHz
–60
–60
–10
–20
–30
IF INPUT POWER EACH TONE (dBm)
–50
–40
–10
–50
–40
–20
–30
IF INPUT POWER EACH TONE (dBm)
–10
5546 G08
5546 G09
Total Harmonic Distortion
vs IF Input Power at 500mV
P-P
Differential Out
–20
–25
–30
f
IF,1
= 280MHz
f
IF,2
= 280.1MHz
f
2xLO
= 570MHz
V
CC
= 3V
0
–1
–2
–40°C
–3
–4
–5
LPF Frequency Response
vs Baseband Frequency
and Temperature
V
CC
= 3V
–40°C
–40
–45
–50
–55
–60
25°C
85°C
25°C
–6
–7
–8
–9
–10
85°C
–10
–65
–40
–35
–30
–25
IF INPUT POWER EACH TONE (dBm)
–20
0
5 10 15 20 25 30 35 40 45 50 55
BASEBAND FREQUENCY (MHz)
5546 G12
5546 G11
IF Detector Output Voltage vs
IF Input CW Power at 3V Supply
1.4
1.2
1.0
85°C
0.8
25°C
0.6
0.4
f
IF
= 280MHz
1.4
1.2
1.0
IF Detector Output Voltage vs
IF Input CW Power at 1.8V Supply
f
IF
= 280MHz
T
A
= 25°C
85°C
0.8
0.6
0.4
25°C
–40°C
–30
–20
–10
0
IF INPUT CW POWER (dBm)
10
5546 G14
–40°C
–30
–20
–10
0
IF INPUT CW POWER (dBm)
10
5546 G15
0.2
–40
0.2
–40
5546fa
5
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