LT5546_15 Datasheet, PDF (1/12 Pages) Linear Technology – 40MHz to 500MHz VGA and I/Q Demodulator with 17MHz Baseband Bandwidth

LT5546
40MHz to 500MHz VGA
and I/Q Demodulator with
17MHz Baseband Bandwidth
FEATURES
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}
U
APPLICATIO S
■ _{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
IF⁺
C2
1µF
15nH
C3
10pF
L2
IF ^–
15nH
GAIN CONTROL
2xLO
560MHz
INPUT
C4
3.3pF
C5
3.3pF
V_CTRL
2xLO⁺
L3
39nH
2xLO^–
EN
÷2
STBY
ENABLE STANDBY
1.8V
C1
1nF
V_CC
GND
I_OUT+
I_OUT–
IF DET
Q_OUT+
Q_OUT–
LT5546
5546 TA01
C3
1.8pF
Total Harmonic Distortion vs
IF Input Level at 1.8V Supply
–25
f_{IF, 1} = 280MHz
–30
f_{IF, 2} = 280.1MHz
f_2xLO = 570MHz
800mV_P-P DIFFERENTIAL OUT
–35
–40
–45
–50
–55
–60
–60 –50 –40 –30 –20 –10
IF INPUT POWER EACH TONE (dBm)
5546 TA01b
5546fa
1