LTC1563-2IGN Linear Technology, LTC1563-2IGN Datasheet - Page 18

• Manufacturer Part Number: LTC1563-2IGN
• Description: IC FILTER LP RC 4TH ORDER 16SSOP
• Manufacturer: Linear Technology

Specifications of LTC1563-2IGN

• Filter Type: Butterworth, Lowpass Switched Capacitor
• Frequency - Cutoff Or Center: 256kHz
• Number Of Filters: 1
• Max-order: 4th
• Voltage - Supply: 2.7 V ~ 11 V, ±2.7 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 16-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

LTC1563-2/LTC1563-3
To design these wideband bandpass filters with the
LTC1563, start with a 4th order lowpass filter and add two
highpass poles with the input, AC coupling capacitors. The
lowpass cutoff frequency and highpass pole frequencies
depend on the specific application. Some experimentation
of lowpass and highpass frequencies is required to achieve
the desired response. FilterCAD does not directly support
this configuration. Use the custom design window in
FilterCAD get the desired response and then use FilterCAD
to give the schematic for the lowpass portion of the filter.
Calculate the two highpass poles using the following
formulae:
The design process is as follows:
1. After starting FilterCAD, select the Enhanced Design
2. Choose a 4th order Bessel or Butterworth lowpass filter
3. Click on the custom response button. This copies the
–5V
18
TYPICAL APPLICATIO S
V
f HPA
O
IN
(
window.
response and set the cutoff frequency to the high
frequency corner of the desired bandpass.
lowpass coefficients into the custom design Coeffi-
cients table.
680pF
C11
4th Order Bessel Lowpass at 128kHz with Two Highpass Poles at 11.7kHz Yields a Wideband Bandpass Centered at 50kHz
)
0.1µF
=
R11
20k
2
• •
π
R21
R31
20k
20k
R
1
11 11
•
C
1
2
3
4
5
6
7
8
,
LP
SA
NC
INVA
NC
LPA
AGND
V
f HPB
–
O
LTC1563-3
(
U
INVB
LPB
NC
NC
SB
NC
EN
V
)
+
=
16
15
14
13
12
11
10
9
2
• •
π
R22
20k
R32
20k
1563 TA09
R
50kHz Wideband Bandpass
1
12
R12
20k
C12
680pF
•
0.1µF
C
12
V
5V
OUT
4. In the Coefficients table, the first two rows are the LP
5. Change the frequency of the highpass (HP1) poles to
6. You may have to perform this loop several times before
7. Once you have reached a satisfactory response, note
8. In the Enhanced Implement window, click on the Active
9. You now have the schematic for the 4th order lowpass
C
11
Type with the f
third and fourth rows and click on the Type column
(currently a hyphen is in this space). Change the Type
of each of these rows to type HP1. This sets up a
template of a 6th order filter with two 2nd order lowpass
sections and two 1st order highpass sections.
get the desired frequency response.
you close in on the correct response.
the highpass pole frequencies. The HP1 highpass poles
must now be removed from the Custom design coeffi-
cients table. After removing the highpass poles, click on
the Implement button to go on to the filter implementa-
tion stage.
RC button and choose the LTC1563-2 part. Click on the
schematic button to view the resulting circuit.
part of the design. Now calculate the capacitor values
from the following formulae:
=
2
• •
π
–10
–20
–30
–40
–50
–60
R
10
0
11
1k
1
O
•
f HPA
and Q as previously defined. Go to the
O
(
10k
FREQUENCY (Hz)
)
,
C
12
=
100k
2
• •
π
1563 TA09a
R
12
1M
1
•
f HPB
O
(
156323fa
)