LT5546
40MHz to 500MHz VGA
and I/Q Demodulator with
17MHz Baseband Bandwidth
FEATURES
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DESCRIPTIO
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17MHz I/Q Lowpass Output Noise Filters
Wide Range 1.8V to 5.25V Supply Voltage
Frequency Range: 40MHz to 500MHz
THD < 0.14% (鈥?7dBc)
at 800mV
P-P
Differential Output Level
IF Overload Detector
Log Linear Gain Control Range: 鈥?dB to 56dB
Baseband I/Q Amplitude Imbalance: 0.2dB
Baseband I/Q Phase Imbalance: 0.6擄
7.8dB Noise Figure at Max Gain
Input IP3 at Low Gain: 鈥?1dBm
Low Supply Current: 24mA
Low Delay Shift Over Gain Control Range: 2ps/dB
Outputs Biased Up While in Standby
16-Lead QFN 4mm
脳
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
廬
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 鈥?dB 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.
TYPICAL APPLICATIO
280MHz
IF INPUT
L1
15nH
C3
10pF
L2
15nH
IF
+
C2
1碌F
C1
1nF
V
CC
1.8V
鈥?5
鈥?0
鈥?5
I
OUT+
I
OUT鈥?/div>
IF
鈥?/div>
THD (dBc)
鈥?0
鈥?5
鈥?0
GAIN CONTROL
2xLO
C4
560MHz
3.3pF
INPUT
V
CTRL
2xLO
+
L3
39nH
2xLO
鈥?/div>
EN
STBY
GND
梅2
IF DET
Q
OUT+
Q
OUT鈥?/div>
LT5546
5546 TA01
C3
1.8pF
鈥?5
鈥?0
鈥?0
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
鈥?0
鈥?0
鈥?0
鈥?0
IF INPUT POWER EACH TONE (dBm)
鈥?0
5546 TA01b
U
U
5546f
1
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