LT5502
400MHz Quadrature
IF Demodulator with RSSI
FEATURES
s
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s
s
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DESCRIPTIO
Single 1.8V to 5.25V Supply
IF Frequency Range: 70MHz to 400MHz
84dB Limiting IF Gain
90dB Linear RSSI Range
7.7MHz Lowpass Output Filter
Baseband I/Q Amplitude Imbalance: <0.7dB
4dB Noise Figure
Low Supply Current: 25mA
Outputs Biased Up While in Standby
Shutdown Current: 1µA
24-Lead Narrow SSOP Package
APPLICATIO S
s
s
s
IEEE802.11
High Speed Wireless LAN
Wireless Local Loop
The LT
®
5502 is a 70MHz to 400MHz monolithic integrated
quadrature IF demodulator. It consists of an IF limiter,
quadrature down mixers, integrated lowpass filters, and
divide-by-two LO buffers. The demodulator provides all
building blocks for demodulation of I and Q baseband
signals with a single supply voltage of 1.8V to 5.25V. The
IF limiter has 84dB small-signal gain, and a built-in receive
signal strength indicator (RSSI) with over 90dB linear
range. The input referred noise-spectral-density is
1.45nV/√Hz, which is equivalent to a 4dB noise figure
when the input is terminated with a 50Ω source. The
integrated lowpass output filters act as antialiasing and
pulse-shaping filters for demodulated I/Q-baseband sig-
nals. The 3dB cutoff frequency of the filters is about
7.7MHz. The VCO frequency is required to be twice the
desired operating frequency to provide quadrature local
oscillator (LO) signals to the mixers. The standby mode
provides fast transient response to the receive mode with
reduced supply current when the I/Q outputs are
AC-coupled to a baseband chip.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
I/Q Output Swing, RSSI Output vs IF Input Power
2V
C2
1µF
C3
22nF
IF
INPUT
R1
240Ω
IF
+
IF
–
2XLO
+
2XLO
INPUT
2XLO
–
LT5502
ENABLE
EN
GND
÷2
0°
C1
1nF
1200
1.2
DIFFERENTIAL OUTPUT SWING (mV
P-P
)
V
CC
1000
I
OUT+
90°
I
OUT–
Q
OUT+
Q
OUT–
RSSI
C4
1.8pF
5502 TA01a
BASEBAND
DIFFERENTIAL
I/Q OUTPUTS
800
600
400
200
–85
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.
U
1.0
U
U
RSSI OUTPUT (V)
0.8
0.6
0.4
0.2
–70
–55
–40
–25
–10
IF INPUT POWER (dBm)
5
5502 TA01b
1
LT5502
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
I
OUT
+
Power Supply Voltage ............................................ 5.5V
LO Input Power .................................................. 10dBm
IF Input Power .................................................... 10dBm
Operating Ambient
Temperature (Note 2) ..............................–40°C to 85°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
Voltage on any Pin not to Exceed ............................. V
CC
1
2
3
4
5
6
7
8
9
24 Q
OUT
+
ORDER PART
NUMBER
LT5502EGN
I
OUT–
GND
V
CC
GND
IF
+
IF
–
GND
GND
23 Q
OUT–
22 V
CC
21 GND
20 GND
19 2XLO
+
18 2XLO
–
17 V
CC
16 V
CC
15 RSSI
14 GND
13 IFt
–
EN 10
STBY 11
IFt
+
12
GN PACKAGE
24-LEAD NARROW PLASTIC SSOP
T
JMAX
= 150°C,
θ
JA
= 85°C/W
Consult factory for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
P
IF
= –50dBm, T
A
= 25°C, unless otherwise noted. (Note 3)
SYMBOL
IF Input
f
IF
Frequency Range
3dB Limiting Sensitivity
Noise Figure
DC Common Mode Voltage
Demodulator I/Q Output
I/Q Output Voltage Swing
I/Q Amplitude Mismatch
I/Q Phase Mismatch
Output Driving Capability
DC Common Mode Voltage
RSSI
Linear Dynamic Range (Note 4)
Output Impedance
Output Voltage
Output Voltage
Output Voltage Slope
Linearity Error
Baseband Lowpass Filter
3dB Cutoff Frequency
Group Delay Ripple
PARAMETER
V
CC
= 3V, f
2XLO
= 570MHz, P
2XLO
= –10dBm, f
IF
= 280MHz,
MIN
TYP
70 to 400
–79
MAX
UNITS
MHz
dBm
dB
V
mV
P-P
0.7
dB
DEG
kΩ
1.84
V
dB
kΩ
0.54
1.2
V
V
mV/dB
dB
MHz
ns
CONDITIONS
Terminated 50Ω Source
4
2.6
Differential
850
0.1
0.6
Differential; C
MAX
= 10pF
1.5
±3dB
Linearity Error
Input = – 70dBm
Input = 0dBm
Input from –70dBm to 0dBm
Input from –70dBm to 0dBm
0.27
0.8
90
3.8
0.41
1.01
8.7
1
7.7
16.4
2
U
W
U
U
W W
W
LT5502
ELECTRICAL CHARACTERISTICS
P
IF
= –50dBm, T
A
= 25°C, unless otherwise noted. (Note 3)
SYMBOL
2XLO
f
2XLO
P
2XLO
Power Supply
V
CC
I
CC
I
OFF
Supply Voltage
Supply Current
Shutdown Current
Standby Mode Current
EN = High
EN = Low; Standby = Low
EN = Low; Standby = High
1.8
25
1
2.6
5.25
32
100
3.5
V
mA
µA
mA
Frequency Range
Input Power
DC Common Mode Voltage
–20
2.6
140 to 800
–5
MHz
dBm
V
PARAMETER
V
CC
= 3V, f
2XLO
= 570MHz, P
2XLO
= –10dBm, f
IF
= 280MHz,
MIN
TYP
MAX
UNITS
CONDITIONS
Note 1:
Absolute Maximum Ratings are those values beyond which the life
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 3.
Note 4:
Tests are performed as shown in the configuration of Figure 1 for
IF input.
TYPICAL PERFOR A CE CHARACTERISTICS
Power Supply Current
vs Temperature
36
T
A
= 85°C
1200
f
IF
= 280MHz
T
A
= 85°C
32
SUPPLY CURRENT (mA)
DIFFERENTIAL OUTPUT SWING (mV
P-P
)
DIFFERENTIAL OUTPUT SWING (mV
P-P
)
28
T
A
= 25°C
24
20
T
A
= –40°C
16
1.8
2.5
4.5
SUPPLY VOLTAGE (V)
3.5
U W
5.5
5502 G01
(Note 3)
I/Q Output Swing vs IF Input Power
1200
V
CC
= 3V
f
IF
= 280MHz
T
A
= 85°C
T
A
= 25°C
I/Q Output Swing vs Temperature
1000
T
A
= 25°C
800
T
A
= –40°C
600
1000
800
600
T
A
= –40°C
400
400
1.8
2.5
4.5
SUPPLY VOLTAGE (V)
3.5
5.5
5502 G02
200
–85
–70
–40
–25
–10
IF INPUT POWER (dBm)
–55
5
5502 G03
3
LT5502
TYPICAL PERFOR A CE CHARACTERISTICS
(Note 3)
I/Q Output Swing vs IF Input Power
1200
DIFFERENTIAL OUTPUT SWING (mV
P-P
)
V
CC
= 3V
T
A
= 25°C
f
IF
= 70MHz
1000
800
f
IF
= 280MHz
600
f
IF
= 400MHz
400
RSSI OUTPUT (V)
RSSI OUTPUT (V)
200
–85
–70
–40
–25
–10
IF INPUT POWER (dBm)
–55
RSSI Output Voltage vs V
CC
1.2
f
IF
= 280MHz
T
A
= 25°C
INPUT SENSITIVITY (dBm)
INPUT SENSITIVITY (dBm)
1.0
RSSI OUTPUT (V)
0.8
V
CC
= 3V
0.6
V
CC
= 5.5V
V
CC
= 1.8V
0.4
0.2
–85
–70
–40
–25
–10
IF INPUT POWER (dBm)
–55
LPF Frequency Response
vs Baseband Frequency
5
0
T
A
= 85°C
GAIN RESPONSE (dB)
–5
GROUP DELAY (ns)
V
CC
= 3V
GAIN RESPONSE (dB)
–10
–15
–20
–25
–30
–35
0
T
A
= 25°C
T
A
= –40°C
16
12
BASEBAND FREQUENCY (MHz)
4
8
4
U W
5
5502 G04
RSSI Output vs Temperature
1.2
V
CC
= 3V
f
IF
= 280MHz
1.2
RSSI Output Voltage vs IF Frequency
V
CC
= 3V
T
A
= 25°C
f
IF
= 280MHz
1.0
1.0
0.8
T
A
= 85°C
0.6
T
A
= –40°C
T
A
= 25°C
0.4
0.8
f
IF
= 70MHz
0.6
0.4
f
IF
= 400MHz
0.2
–85
0.2
–85
–70
–40
–25
–10
IF INPUT POWER (dBm)
–55
5
–70
–55 –40
–25
–10
IF INPUT POWER (dBm)
5
5502 G05
5502 G06
IF Input Sensitivity
vs Temperature
–73
f
IF
= 280MHz
–73
IF Input Sensitivity vs IF Frequency
V
CC
= 3V
–75
–76
T
A
= 85°C
–79
T
A
= 25°C
–82
T
A
= –40°C
–77
T
A
= 25°C
–79
T
A
= 85°C
T
A
= –40°C
–81
5
–83
1.8
2.5
4.5
SUPPLY VOLTAGE (V)
3.5
–85
5.5
5502 G08
70 100
150 200 250 300
IF FREQUENCY (MHz)
350
400
5502 G07
5502 G09
LPF Group Delay
vs Baseband Frequency
110
95
80
65
50
35
20
T
A
= 25°C
T
A
= 85°C
V
CC
= 3V
LPF Frequency Response vs V
CC
5
0
–5
–10
–15
–20
–25
–30
50
70
V
CC
= 1.8V, 3V, 5.5V
T
A
= 25°C
110
T
A
= –40°C
90
GROUP DELAY (ns)
20
5502 G10
0
4
8
12
16
BASEBAND FREQUENCY (MHz)
20
5502 G11
–35
0
16
12
BASEBAND FREQUENCY (MHz)
4
8
30
20
5502 G12
LT5502
PI FU CTIO S
I
OUT+
(Pin 1):
Positive Baseband Output Pin of I-Channel.
The DC bias voltage is V
CC
– 1.16V. This pin should not be
shorted to ground.
I
OUT–
(Pin 2):
Negative Baseband Input Pin of I-Channel.
The DC bias voltage is V
CC
– 1.16V. This pin should not be
shorted to ground.
GND (Pins 3, 5, 8, 9, 14, 20, 21):
Ground Pin.
V
CC
(Pins 4, 16, 17, 22):
Power Supply Pin. This pin
should be decoupled using 1000pF and 0.1µF capacitors.
IF
+
(Pin 6):
Positive IF Input Pin. The DC bias voltage is
V
CC
– 0.4V.
IF
–
(Pin 7):
Negative IF Input Pin. The DC bias voltage is
V
CC
– 0.4V.
EN (Pin 10):
Enable Pin. When the input voltage is higher
than 0.9V or up to V
CC
, the circuit is completely turned on.
When the input voltage is less than 0.7V or down to
ground, the circuit is turned off except the part of the
circuit associated with standby mode.
STBY (Pin 11):
Standby Pin. When the input voltage is
higher than 0.9V or up to V
CC
, the circuit of standby mode
is turned on to bias the I/Q buffers to desired quiescent
voltage. When the input voltage is less than 0.7V or down
to ground, it is turned off.
IFt
+
(Pin 12):
Interstage IF Positive Pin. The DC bias
voltage is V
CC
– 0.25V.
IFt
–
(Pin 13):
Interstage IF Negative Pin. The DC bias
voltage is V
CC
– 0.25V.
RSSI (Pin 15):
RSSI Output Pin.
2XLO
–
(Pin 18):
Negative Carrier Input Pin. The input-
signal’s frequency must be twice that of the desired
demodulator LO frequency. The DC bias voltage is V
CC
–
0.4V.
2XLO
+
(Pin 19):
Positive Carrier Input Pin. The input-
signal’s frequency must be twice that of the desired
demodulator LO frequency. The DC bias voltage is V
CC
–
0.4V.
Q
OUT–
(Pin 23):
Negative Baseband Output Pin of the
Q-Channel. The DC bias voltage is V
CC
– 1.16V. This pin
should not be shorted to ground.
Q
OUT+
(Pin 24):
Positive Baseband Output Pin of the
Q-Channel. The DC bias voltage is V
CC
– 1.16V. This pin
should not be shorted to ground.
BLOCK DIAGRA
IF
+
IF
–
6
7
W
U
U
U
IFt
+
12
IFt
–
13
I-MIXER
LPF
1
2
LO
BUFFERS
DIVIDE 2
0°/90°
I
OUT–
1
I
OUT+
LIMITER
1
LIMITER
2
LPF
1
24
Q
OUT+
23
Q
OUT–
BIAS
RSSI
Q-MIXER
15
RSSI
19
2XLO
+
18
2XLO
–
10
EN
5502 BD
5
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