Document
U U
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 800mVP-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 linearin-dB relationship to the control input voltage. Hard-clipping 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 15nH
C3 10pF
L2 15nH
IF+ IF –
C2 1µF
GAIN CONTROL
2xLO 560MHz
INPUT
C4 3.3pF
C5 3.3pF
VCTRL 2xLO+
L3 39nH
2xLO–
EN
÷2 STBY
ENABLE STANDBY
1.8V C1 1nF
VCC
GND
IOUT+ IOUT– IF DET QOUT+ QOUT–
LT5506
5506 TA01
C3 1.8pF
THD (dBc)
Total Harmonic Distortion vs IF Input Level at 1.8V Supply
–30 fIF, 1 = 280MHz fIF, 2 = 280.1MHz
–35 f2xLO = 570MHz 800mVP-P DIFFERENTIAL OUT
–40
–45
–50
–55
–60 –60 –50 –40 –30 –20 –10 IF INPUT POWER EACH TONE (dBm)
5506 TA01b
5506fa
1
U WW W
LT5506
ABSOLUTE AXI U RATI GS
(Note 1)
Supply Voltage ....................................................... 5.5V Differential Voltage Between 2xLO+ and 2xLO–.......... 4V IF+, IF– ............................................. –500mV to 500mV IOUT+, IOUT–, QOUT+, QOUT– .................. VCC – 1.8V to VCC 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 VCC + 500mV
UW U PACKAGE/ORDER I FOR ATIO
TOP VIEW
IOUT+ IOUT– QOUT+ QOUT–
16 15 14 13
GND 1
12 STBY
IF+ 2
11 2xLO+
IF– 3 17 10 2xLO–
GND 4
9 EN
5678
ORDER PART NUMBER
LT5506EUF
VCC VCTRL IF DET
VCC
UF PACKAGE 16-LEAD (4mm × 4mm) PLASTIC QFN
TJMAX = 125°C, θJA = 37°C/W EXPOSED PAD (PIN 17) IS GROUND
MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS VCC = 3V. f2xLO = 570MHz, P2xLO = –5dBm (Note 5), fIF = 284MHz,
PIF = –30dBm, I and Q outputs 800mVP-P into 4kΩ differential load, TA = 25°C, EN = VCC, STBY = VCC, unless otherwise noted. (Note 3)
SYMBOL IF Input fIF
PARAMETER
Frequency Range Nominal Input Level Input Impedance
NF Noise Figure at Max Gain GL Min Gain (Note 4) GH Max Gain (Note 4) IIP3 Input IP3, Min Gain
Input IP3, Max Gain IIP2 Input IP2, Max Gain Demodulator I/Q Output
Nominal Voltage Swing Clipping Level DC Common Mode Voltage I/Q Amplitude Imbalance I/Q Phase Imbalance DC Offset Output Driving Capability STBY to Turn-On Delay I/Q Output 1dB Compression I/Q Output IM3
CONDITIONS
RSOURCE = 200Ω Differential IF+, IF– to GND, EN = VCC IF+, IF– to GND, EN = GND VCTRL = 1.7V VCTRL = 0.2V VCTRL = 1.7V PIF = –22.5dBm (Note 7) PIF = –75dBm (Note 7) VCTRL = 1.7V
(Note 6) (Note 6)
(Note 8) (Note 8) (Notes 6, 8) Single Ended, CLOAD ≤ 10pF
PIF, 1 = –25.5dBm, 280MHz PIF, 2 = –25.5dBm, 280.1MHz (Note 7)
MIN TYP MAX UNITS
40 to 500 –79 to –22 100Ω//1.2pF
1pF 6.8 0.9 50 59 – 0.5 – 49 –8
8
MHz dBm
dB dB dB dBm dBm dBm
0.8 1.25 VCC – 1.19 0.2 0.5 0.6 3 28 2 1.5 0.3 –11.5 – 50
VP-P VP-P
V dB Deg mV kΩ µs dBm dBc
5506fa
2
LT5506
ELECTRICAL CHARACTERISTICS VCC = 3V. f2×LO = 570MHz, P2×LO = –5dBm (Note 5), fIF = 284MHz,
PIF = –30dBm, I and Q outputs 800mVP-P into 4kΩ differential load, TA = 25°C, EN = VCC, STBY = VCC, unless otherwise noted. (Note 3)
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Variable Gain Amplifier (VGA)
Gain Slope Linearity Error Temperature Gain Shift Gain Control Response Time
VCTRL = 0V to 1.4V T = –40°C to 85°C, .