LTC6603_15 Datasheet, PDF (1/24 Pages) Linear Technology – Dual Adjustable Lowpass Filter

FEATURES
n _{Guaranteed Phase and Gain Matching Specs}
n _{Programmable BW Up to 2.5MHz}
n _{Programmable Gain (0dB/6dB/12dB/24dB)}
n _{9th Order Linear Phase Response}
n _{Differential, Rail-to-Rail Inputs and Outputs}
n _{Low Noise: –145dBm/Hz (Input Referred)}
n _{Low Distortion: –75dBc at 200kHz}
n _{Simple Pin Programming or SPI Interface}
n _{Set the Max Speed/Power with an External R}
n _{Operates from 2.7V to 3.6V}
n _{Input Range from 0V to 5.5V}
n _{4mm × 4mm QFN Package}
APPLICATIONS
n _{Small/Low Cost Basestations:}
IDEN, PHS, TD-SCDMA, CDMA2000, WCDMA,
UMTS
n _{Low Cost Repeaters, Radio Links, and Modems}
n _{802.11x Receivers}
n _JTRS
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
LTC6603
Dual Adjustable
Lowpass Filter
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.
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.
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
I_IN
Q_IN
0.1μF
30.9k
0.1μF
BASEBAND
GAIN CONTROL
2.5MHz I and Q Lowpass Filter and Dual ADC
5V
3V
49.9Ω 100nH*
0.1μF
0.1μF
V+_IN
V+_A V+_D
+INA
–INA
+INB
–INB
R_BIAS
+OUTA
–OUTA
+OUTB
LTC6603 _–OUTB
CLKIO
V_OCM
SER
I OUTPUT
49.9Ω 100nH*
49.9Ω 100nH*
Q OUTPUT
49.9Ω 100nH*
180pF
10pF
180pF
10pF
180pF
10pF
180pF
10pF
CAP
CLKCNTL
3V
V_CM
LTC2297
14-BIT
ADC
14-BIT
ADC
GAIN1
GAIN0
GND
GND
SDO
SDI
LPFO
3V
LPF1
2.2μF
*COILCRAFT 0603HP
6603 TA01a
Phase Matching
60
V_S = 3V, BW = 156.25kHz
f = 125kHz, T_A = 25°C
50 1000 UNITS
40
30
20
10
0
–2.5 –2 –1.5 –1 –0.5 0 0.5 1 1.5 2 2.5
MISMATCH (DEG)
6603 TA01b
6603fa
1