LTC1569-6 Datasheet, PDF (1/12 Pages) Linear Technology – Linear Phase, DC Accurate, Low Power, 10th Order Lowpass Filter

Final Electrical Specifications
LTC1569-6
Linear Phase, DC Accurate,
Low Power, 10th Order Lowpass Filter
September 1999
FEATURES
s _{One External R Sets Cutoff Frequency}
s _{Root Raised Cosine Response}
s _{3mA Supply Current with a Single 3V Supply}
s _{Up to 64kHz Cutoff on a Single 3V Supply}
s _{10th Order, Linear Phase Filter in an SO-8}
s _{DC Accurate, VOS(MAX) = 5mV}
s _{Low Power Modes}
s _{Differential or Single-Ended Inputs}
s _{80dB CMRR (DC)}
s _{82dB Signal-to-Noise Ratio, VS = 5V}
s _{Operates from 3V to ±5V Supplies}
U
APPLICATIO S
s _{Data Communication Filters for 3V Operation}
s _{Linear Phase and Phase Matched Filters for I/Q}
Signal Processing
s _{Pin Programmable Cutoff Frequency Lowpass Filters}
DESCRIPTIO
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-
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 • f_CUTOFF, 60db
at 2 • f_CUTOFF, and in excess of 80dB at 6 • f_CUTOFF. DC-
accuracy-sensitive applications benefit from the 5mV
maximum DC offset.
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.
TYPICAL APPLICATIO
Single 3V Supply, 64kHz/16kHz/4kHz Lowpass Filter
Frequency Response, f_CUTOFF = 64kHz/16kHz/4kHz
0
3V
3.48k
2k
V_IN ¹ IN⁺
2 _IN–
OUT ⁸ V_OUT
V^{+ 7 REXT = 10k}
LTC1569-6
3 _GND
R_X ⁶
1µF
4 _V–
1/16
DIV/CLK ⁵
1/4
EASY TO SET f_CUTOFF:
1/1
f_CUTOFF = ^{64kHz (10k/REXT)}
1, 4 OR 16
3V
1µF
3V
100pF
1569-6 TA01
–20
–40
–60
–80
–100
1
10
100
FREQUENCY (kHz)
1000
1569-6 TA01a
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.
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