LTC1068 Series
Clock-Tunable, Quad
Second Order, Filter Building Blocks
U
DESCRIPTIO
EATURE
Four Identical 2nd Order Filter Sections in an
S
F
The LTC®1068 product family consists of four monolithic
clock-tunablefilterbuildingblocks.Eachproductcontains
fourmatched,lownoise,highaccuracy2ndorderswitched-
capacitorfiltersections. Anexternalclocktunesthecenter
frequency of each 2nd order filter section. The LTC1068
products differ only in their clock-to-center frequency
ratio. The clock-to-center frequency ratio is set to 200:1
(LTC1068-200), 100:1 (LTC1068), 50:1 (LTC1068-50) or
25:1 (LTC1068-25). External resistors can modify the
clock-to-center frequency ratio. High performance, quad
2nd order, dual 4th order or 8th order filters can be
designed with an LTC1068 family product. Designing
filters with an LTC1068 product is fully supported by
FilterCADTM filter design software for Windows®.
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SSOP Package
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2nd Order Section Center Frequency Error:
±
0.3% Typical and
±0.8% Maximum
Low Noise per 2nd Order Section, Q ≤ 5:
LTC1068-200 50µV
LTC1068-50 75µV
, LTC1068 50µV
RMS RMS
, LTC1068-25 90µV
RMS
RMS
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Low Power Supply Current: 4.5mA, Single 5V,
LTC1068-50
Operation with ±5V Power Supply, Single 5V
Supply or Single 3.3V Supply
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PPLICATI
A
S
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Lowpass or Highpass Filters:
The LTC1068 products are available in a 28-pin SSOP
surface mount package. A customized version of an
LTC1068 family product can be obtained in a 16-lead SO
package with internal thin-film resistors. Please contact
LTC Marketing for details.
LTC1068-200, 0.5Hz to 25kHz; LTC1068, 1Hz to
50kHz; LTC1068-50, 2Hz to 50kHz; LTC1068-25,
4Hz to 200kHz
Bandpass or Bandreject (Notch) Filters:
LTC1068-200, 0.5Hz to 15kHz; LTC1068, 1Hz to
30kHz; LTC1068-50, 2Hz to 30kHz; LTC1068-25,
4Hz to 140kHz
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, LTC and LT are registered trademarks of Linear Technology Corporation.
FilterCAD is a trademark of Linear Technology Corporation.
Windows is a registered trademark of Microsoft Corporation.
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O
TYPICAL APPLICATI
Dual, Matched, 4th Order Butterworth Lowpass Filters, Clock-Tunable
Up to 200kHz f – 3dB = fCLK/25, 4th Order Filter Noise = 60µVRMS
R12 14k
R11 20k
1
2
28
27
26
25
24
23
22
21
20
19
18
17
16
15
V
INV B
HPB/NB
BPB
INV C
HPC/NC
BPC
IN1
R21 14k
R31 20k
R22 20k
R32 10k
Gain vs Frequency
3
10
0
4
V
LPB
LPC
OUT1
5
–10
–20
–30
–40
–50
–60
–70
–80
SB
SC
LTC1068-25
6
–
–5V
NC
V
1µF
7
AGND
NC
CLK
8
+
5V
f
= (25)(f – 3dB)
CLK
V
0.1µF
9
NC
NC
10
11
12
13
14
SA
SD
V
LPA
LPD
OUT2
R33 20k
R23 14k
R34 10k
R24 20k
BPA
HPA/NA
INVA
BPD
0.1
1
10
RELATIVE FREQUENCY [f /(f – 3dB)]
IN
HPD/ND
INVD
R13 20k
1068 TA20b
V
IN2
R14 14k
1068 TA20a
1