LTC1062_09 Datasheet, PDF (1/16 Pages) Linear Technology – 5th Order Lowpass Filter

LTC1062
5th Order Lowpass Filter
FEATURES
■ _{Lowpass Filter with No DC Error}
■ _{Low Passband Noise}
■ _{Operates DC to 20kHz}
■ _{Operates On a Single 5V Supply or Up to ±8V}
■ _{5th Order Filter}
■ _{Maximally Flat Response}
■ _{Internal or External Clock}
■ _{Cascadable for Faster Rolloff}
■ _{Buffer Available}
U
APPLICATIO S
■ _{60Hz Lowpass Filters}
■ _{Antialiasing Filter}
■ _{Low Level Filtering}
■ _{Rolling Off AC Signals from High DC Voltages}
■ _{Digital Voltmeters}
■ _Scales
■ _{Strain Gauges}
TYPICAL APPLICATIO
10Hz 5th Order Butterworth Lowpass Filter
25.8k
V_IN
V^– = –5V
1µF
1
FB
2
AGND
8
B_OUT
7
OUT
DC ACCURATE
OUTPUT
BUFFERED
OUTPUT
LTC1062
3 _V–
V^{+ 6}
4
5
DIVIDER C_OSC
RATIO
C_OSC=
3900pF
V⁺ = 5V
1062 TA01
NOTE: TO ADJUST OSCILLATOR FREQUENCY,
USE A 6800pF CAPACITOR IN SERIES
WITH A 50k POT FROM PIN 5 TO GROUND
DESCRIPTIO
The LTC^®1062 is a 5th order all pole maximally flat
lowpass filter with no DC error. Its unusual architecture
puts the filter outside the DC path so DC offset and low
frequency noise problems are eliminated. This makes the
LTC1062 very useful for lowpass filters where DC accuracy
is important.
The filter input and output are simultaneously taken across
an external resistor. The LTC1062 is coupled to the signal
through an external capacitor. This RC reacts with the
internal switched capacitor network to form a 5th order
rolloff at the output.
The filter cutoff frequency is set by an internal clock that
can be externally driven. The clock-to-cutoff frequency
ratio is typically 100:1, allowing the clock ripple to be
easily removed.
Two LTC1062s can be cascaded to form a 10th order quasi
max flat lowpass filter. The device can be operated with
single or dual supplies ranging from ±2.5V to ±9V.
The LTC1062 is manufactured using Linear Technology’s
enhanced LTCMOS^TM silicon gate process.
, LTC and LT are registered trademarks of Linear Technology Corporation.
LTCMOS is a trademark of Linear Technology Corporation.
Filter Amplitude Response and Noise
0
C_OSC = 3900pF
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
1
10
INPUT FREQUENCY (Hz)
50
40
30
20
10
0
100
1062 TA02
1062fd
1