LTC6603
Dual Adjustable
Lowpass Filter
FEATURES
DESCRIPTION
The LTC®6603 is a dual, matched, programmable lowpass
filter for communications receivers and transmitters. The
selectivity of the LTC6603, combined with its linear phase,
phase matching and dynamic range, make it suitable for
filtering in many communications systems. With 1.5°
phase matching between channels, the LTC6603 can be
used in applications requiring pairs of matched filters,
such as transceiver I and Q channels. Furthermore, the
differential inputs and outputs provide a simple interface
for most communications systems.
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Guaranteed Phase and Gain Matching Specs
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Programmable BW Up to 2.5MHz
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Programmable Gain (0dB/6dB/12dB/24dB)
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9th Order Linear Phase Response
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Differential, Rail-to-Rail Inputs and Outputs
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Low Noise: –145dBm/Hz (Input Referred)
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Low Distortion: –75dBc at 200kHz
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Simple Pin Programming or SPI Interface
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Set the Max Speed/Power with an External R
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Operates from 2.7V to 3.6V
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Input Range from 0V to 5.5V
The sampled data filter does not require an external clock
yet its cutoff frequency can be set with a single external
resistor with an accuracy of 3.5% or better. The external
resistor programs an internal oscillator whose frequency
is divided prior to being applied to the filter networks.
This allows up to three cutoff frequencies that can be
obtained for each external resistor value, allowing the
cutoff frequency to be programmed over a range of more
than six octaves. Alternatively, the cutoff frequency can
be set with an external clock. The filter gain can also be
programmed to 1, 2, 4 or 16.
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4mm × 4mm QFN Package
APPLICATIONS
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Small/Low Cost Basestations:
IDEN, PHS, TD-SCDMA, CDMA2000, WCDMA,
UMTS
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Low Cost Repeaters, Radio Links, and Modems
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802.11x Receivers
JTRS
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L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
The LTC6603 features a low power shutdown mode that
can be programmed through the serial interface and is
available in a 24-pin 4mm × 4mm QFN package.
TYPICAL APPLICATION
2.5MHz I and Q Lowpass Filter and Dual ADC
5V
3V
LTC2297
100nH*
49.9Ω
Phase Matching
0.1μF
0.1μF
180pF
180pF
10pF
10pF
60
I OUTPUT
14-BIT
ADC
V
= 3V, BW = 156.25kHz
S
f = 125kHz, T = 25°C
V+
V+
V+
D
A
IN
A
50 1000 UNITS
100nH*
49.9Ω
+INA
–INA
+INB
–INB
+OUTA
–OUTA
+OUTB
–OUTB
CLKIO
I
IN
40
30
20
10
0
100nH*
49.9Ω
Q
IN
LTC6603
R
180pF
180pF
10pF
10pF
BIAS
0.1μF
0.1μF
Q OUTPUT
100nH*
14-BIT
ADC
30.9k
V
SER
OCM
49.9Ω
V
CM
3V
3V
CAP
CLKCNTL
–2.5 –2 –1.5 –1 –0.5
0
0.5
1
1.5
2
2.5
2.2μF
GAIN1
GAIN0
SDO
SDI
MISMATCH (DEG)
6603 TA01b
GND
GND
LPFO
LPF1
*COILCRAFT 0603HP
BASEBAND
GAIN CONTROL
6603 TA01a
6603f
1