LT5506_15 Datasheet, PDF (1/12 Pages) Linear Technology – 40MHz to 500MHz Quadrature Demodulator with VGA

LT5506
FEATURES
s _{Wide Range 1.8V to 5.25V Supply}
s _{Frequency Range: 40MHz to 500MHz}
s _{–4dB to 59dB Variable Power Gain}
s _{THD < 0.12% (–58dBc)}
at 800mV_P-P Differential Output Level
s _{8.8MHz I/Q Lowpass Output Noise Filters}
s _{IF Overload Detector}
s _{Baseband I/Q Amplitude Imbalance: 0.2dB}
s _{Baseband I/Q Phase Imbalance: 0.6°}
s _{6.8dB Noise Figure at Max Gain}
s _{Input IP3 at Low Gain: – 0.5dBm}
s _{Low Supply Current: 27mA}
s _{Low Delay Shift Over Gain Control Range: 2ps/dB}
s _{Outputs Biased Up While in Standby}
s _{16-Lead QFN 4mm x 4mm Package with Exposed Pad}
U
APPLICATIO S
s _IEEE802.11
s _{High Speed Wireless LAN}
s _{Wireless Local Loop}
40MHz to 500MHz
Quadrature Demodulator
with VGA
DESCRIPTIO
The LT^®5506 is a 40MHz to 500MHz monolithic integrated
quadrature demodulator with variable gain amplifier (VGA),
designed for low voltage operation. It supports standards
that use a linear modulation format. The chip consists of
a VGA, quadrature down-converting mixers and lowpass
noise filters. 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 cut-off frequency of the noise filters is
approximately 8.8MHz. The external 2xLO frequency is
required to be twice the IF input frequency for the mixers.
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
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–
LT5506
5506 TA01
C3
1.8pF
Total Harmonic Distortion vs
IF Input Level at 1.8V Supply
–30
f_{IF, 1} = 280MHz
f_{IF, 2} = 280.1MHz
–35 f_2xLO = 570MHz
800mV_P-P DIFFERENTIAL OUT
–40
–45
–50
–55
–60
–60 –50 –40 –30 –20 –10
IF INPUT POWER EACH TONE (dBm)
5506 TA01b
5506fa
1