LTC1065
DC Accurate, Clock-Tunable
Linear Phase 5th Order Bessel
Lowpass Filter
FEATURES
s
s
s
s
s
s
s
s
s
s
s
s
DESCRIPTIO
Clock-Tunable Cutoff Frequency
1mV DC Offset (Typical)
80dB CMR (Typical)
Internal or External Clock
50碌V
RMS
Clock Feedthrough
100:1 Clock-to-Cutoff Frequency Ratio
80碌V
RMS
Total Wideband Noise
0.004% Noise + THD at 2V
RMS
Output Level
50kHz Maximum Cutoff Frequency
Cascadable for Faster Roll-Off
Operates from
鹵2.375
to
鹵8V
Power Supplies
Self-Clocking with 1 RC
The LTC1065 is the first monolithic filter providing both
clock-tunability with low DC output offset and over 12-bit
DC accuracy. The frequency response of the LTC1065
closely approximates a 5th order Bessel polynomial. With
appropriate PCB layout techniques the output DC offset is
typically 1mV and is constant over a wide range of clock
frequencies. With
鹵5V
supplies and
鹵4V
input voltage
range, the CMR of the device is typically 80dB.
The filter cutoff frequency is controlled either by an inter-
nal or external clock. The clock-to-cutoff frequency ratio is
100 : 1. The on-board clock is nearly power supply inde-
pendent and it is programmed via an external RC. The
50碌V
RMS
clock feedthrough of the device is considerably
lower than other existing monolithic filters.
The LTC1065 wideband noise is 80碌V
RMS
and it can
process large AC input signals with low distortion. With
鹵
7.5V supplies, for instance, the filter handles up to
4V
RMS
(94dB S/N ratio) while the standard 1kHz THD is
below 0.005%; 87dB dynamic range (S/N + THD) is ob-
tained with input levels between 2V
RMS
and 2.5V
RMS
.
The LTC1065 is available in 8-pin miniDIP and 16-pin SOL.
For a Butterworth response, see LTC1063 data sheet. The
LTC1065 is pin compatible with the LTC1063.
APPLICATI
s
s
s
s
s
s
s
S
Audio
Strain Gauge Amplifiers
Anti-Aliasing Filters
Low Level Filtering
Digital Voltmeters
Smoothing Filters
Reconstruction Filters
TYPICAL APPLICATI
5V
4.99k
V
IN
1
2
3.4kHz Single 5V Supply Bessel Lowpass Filter
10
0
8
7
LTC1065
6
5
V
OUT
5V
0.1碌F
鈥?0
鈥?0
GAIN (dB)
+
1碌F
TANT
4.53k
0.1碌F 3
4
鈥?0
鈥?0
鈥?0
鈥?0
13k*
*
SELF-CLOCKING SCHEME
200pF*
1065 TA01
鈥?0
鈥?0
鈥?0
1
10
FREQUENCY (kHz)
100
1065 TA02
U
Frequency Response
UO
UO
1