LTC1563-2IGN View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1563-2IGN' PDF : 20 Pages View PDF
LTC1563-2/LTC1563-3
TYPICAL APPLICATIO S
100kHz, 6th Order Pseudo-Butterworth
RA1 3.16k
VIN
RB1 29.4k
C11
560pF
R31
17.8k
R21
32.4k
0.1µF
LTC1563-2
1 LP
2
SA
3
NC
4
INVA
5
NC
6
LPA
7
AGND
8 V–
V+ 16
15
LPB
14
NC
13
INVB
12
NC
11
SB
10
NC
9
EN
R22
28.7k
R32
20.5k
3.3V
0.1µF
VOUT
RA2 3.16k RB2 25.5k
C12
560pF
1563 TA07
TEXTBOOK BUTTERWORTH
fO1 = 100kHz
fO2 = 100kHz
fO3 = 100kHz
Q1 = 1.9319
Q2 = 0.7071
Q3 = 0.5176
PSEUDO-BUTTERWORTH
fO1 = 100kHz
fO2 = 100kHz
fO3 = 100kHz
fO4 = 100kHz
Q1 = 1.9319
Q2 = 0.7358
Real Poles
Real Poles
Frequency Response
10
0
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
10k
100k
FREQUENCY (Hz)
1M
1563 TA07a
The complex, 2nd order section of the textbook design
with the lowest Q is replaced with two real first order poles.
The Q of another section is slightly altered such that the
final filter’s response is indistinguisable from a textbook
Butterworth response.
Other Pseudo Filter Response Coefficients (All fO Are Normalized for a 1Hz Filter Cutoff)
BESSEL 0.1dB RIPPLE CHEBYSHEV 0.5dB RIPPLE CHEBYSHEV TRANSITIONAL GAUSSIAN TO 12dB
fO1 1.9070
Q1 1.0230
1.0600
3.8500
1.0100
5.3000
2.1000
2.2000
fO2 1.6910
Q2 0.6110
0.8000
1.0000
0.7200
1.2000
1.2500
0.8000
fO3 1.6060
fO4 1.6060
0.6000
1.0000
0.5000
0.8000
1.2500
1.2500
TRANSITIONAL GAUSSIAN TO 6dB
1.5000
2.8500
1.0500
0.9000
0.9000
0.9000
The fO and Q values listed above can be entered in
FilterCAD’s Enhanced Design window as a custom re-
sponse filter. After entering the coefficients, FilterCAD will
produce a schematic of the circuit. The procedure is as
follows:
1. After starting FilterCAD, select the Enhanced Design
window.
2. Select the Custom Response and set the custom FC to
1Hz.
3. In the Coefficients table, go to the Type column and click
on the types listed and set the column with two LP types
and two LP1 types. This sets up a template of a 6th order
filter with two 2nd order lowpass sections and two 1st
order lowpass sections.
16
4. Enter the fO and Q coefficients as listed above. For a
Butterworth filter, use the same coefficients as the
example circuit above except set all of the fO to 1Hz.
5. Set the custom FC to the desired cutoff frequency. This
will automatically multiply all of the fO coefficients. You
have now finished the design of the filter and you can
click on the frequency response or step response
buttons to verify the filter’s response.
6. Click on the Implement button to go on to the filter
implementation stage.
7. In the Enhanced Implement window, click on the Active
RC button to choose the LTC1563-2 part. You are now
done with the filter’s implementation. Click on the
schematic button to view the resulting circuit.
156323fa
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