Final Electrical Specifications
LTC1569-6
Linear Phase, DC Accurate,
Low Power, 10th Order Lowpass Filter
September 1999
FEATURES
s
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One External R Sets Cutoff Frequency
Root Raised Cosine Response
3mA Supply Current with a Single 3V Supply
Up to 64kHz Cutoff on a Single 3V Supply
10th Order, Linear Phase Filter in an SO-8
DC Accurate, V
OS(MAX)
= 5mV
Low Power Modes
Differential or Single-Ended Inputs
80dB CMRR (DC)
82dB Signal-to-Noise Ratio, V
S
= 5V
Operates from 3V to
鹵5V
Supplies
tems.
Furthermore, its root raised cosine response offers
the optimum pulse shaping for PAM data communica-
tions.
The filter attenuation is 50dB at 1.5 鈥?f
CUTOFF
, 60db
at 2 鈥?f
CUTOFF
, and in excess of 80dB at 6 鈥?f
CUTOFF
. DC-
accuracy-sensitive applications benefit from the 5mV
maximum DC offset.
APPLICATIO S
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Data Communication Filters for 3V Operation
Linear Phase and Phase Matched Filters for I/Q
Signal Processing
Pin Programmable Cutoff Frequency Lowpass Filters
DESCRIPTIO
廬
The LTC1569-6 sampled data filter does not require an
external clock yet its cutoff frequency can be set with a
single external resistor with a typical accuracy of 3.5% or
better.
The external resistor programs an internal oscilla-
tor whose frequency is divided by either 1, 4 or 16 prior to
being applied to the filter network. Pin 5 determines the
divider setting. Thus, up to three cutoff frequencies can be
obtained for each external resistor value. Using various
resistor values and divider settings, the cutoff frequency
can be programmed over a range of six octaves. Alterna-
tively, the cutoff frequency can be set with an external
clock and the clock-to-cutoff frequency ratio is 64:1. The
ratio of the internal sampling rate to the filter cutoff
frequency is 128:1.
The LTC1569-6 is fully tested for a cutoff frequency of
64kHz with a single 3V supply.
The LTC1569-6 features power saving modes and it is
available in an SO-8 surface mount package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
The LTC 1569-6 is a 10th order lowpass filter featuring
linear phase and a root raised cosine amplitude response.
The high selectivity of the LTC1569-6 combined with its
linear phase in the passband makes it suitable for filtering
both in data communications and data acquisition sys-
TYPICAL APPLICATIO
Single 3V Supply, 64kHz/16kHz/4kHz Lowpass Filter
V
IN
3V
3.48k
3
2k
1碌F
4
V
鈥?/div>
DIV/CLK
5
1/1
1
2
IN
+
IN
鈥?/div>
OUT
V
+
8
7
V
OUT
R
EXT
= 10k
1碌F
6
1/16
1/4
3V
GAIN (dB)
3V
LTC1569-6
GND
R
X
EASY TO SET f
CUTOFF
:
f
CUTOFF
=
1, 4 OR 16
64kHz (10k/R
EXT
)
1569-6 TA01
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
U
U
U
Frequency Response, f
CUTOFF
= 64kHz/16kHz/4kHz
0
鈥?0
鈥?0
鈥?0
鈥?0
100pF
鈥?00
1
10
100
FREQUENCY (kHz)
1000
1569-6
TA01a
1
1
2
3
4
5
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