428 Series
10 Hz - 102.4 kHz
4-Bit Programmable
Description
The 428 Series are 8-pole digitally programmable
low-pass and high-pass active filters. These new
filters take advantage of the company’s proprietary
designs using surface-mount technology to provide
a low profile, compact package in minimal board
space. 428 filters are factory tuned to one of ten
preset 4-bit binary ranges from 10 Hz to 102.4 kHz.
Contact the factory for custom discrete tuning
ranges, maximum span 1000:1.
All 428 Series models are easy to use fully finished
filters which require no external components or
adjustment. They feature low harmonic distortion,
near theoretical phase and amplitude characteristics
and operate over a dynamic input voltage range
from non-critical ±12V to ±18V power supplies.
Features/Benefits:
• Low harmonic distortion and wide signal-to-noise
ratio to 16-bit resolution.
• Compact 1.8"L x 0.8"W x 0.3"H min. (32-pin DIP
footprint) minimizes board space requirements.
• Digitally programmable corner frequency allows
selecting cut-off frequencies specific to each
application.
• Plug-in ready-to-use, reducing engineering design
and manufacturing cycle time.
• Factory tuned, no external clocks or adjustments
needed.
• Broad range of transfer characteristics and corner
frequencies to meet a wide range of applications.
Applications
• Anti-alias filtering
• Data acquisition systems
• Communication systems and electronics
• Medical electronics equipment and research
• Aerospace, navigation and sonar applications
• Acoustic and vibration analysis and control
• Real and compressed time data analysis
• Noise elimination
• Signal reconstruction
Programmable Specifications:
. . . . . . . . . . . . .
Page
Digital Tuning & Control . . . . . . . . . . . . . . . . . . . . . . . 2
Available Low-Pass Models:
. . . . . . . . . . . . . . . . . . .
428L4B
8-pole Butterworth . . . . . . . . . . . . . . . . . . 3
428L4E
8-pole, 6 zero elliptic, 1.77 (-80dB) . . . . . . 3
428L4EX
8-pole, 6 zero elliptic, 1.56 (-80dB) . . . . . . 3
428L4EY
8-pole, 6 zero elliptic, 2.00 (-100dB) . . . . . 3
428L4L
8-pole Bessel . . . . . . . . . . . . . . . . . . . . . . 4
428L4D60
8-pole constant delay (-60dB). . . . . . . . . . 4
428L4D80
8-pole constant delay (-80dB). . . . . . . . . . 4
428L4D10
8-pole constant delay (-100dB) . . . . . . . . . 4
Available High-Pass Models:
. . . . . . . . . . . . . . . . . .
428H4B
8-pole Butterworth . . . . . . . . . . . . . . . . . . 5
428H4E
8-pole, 6 zero elliptic, 1.77 (-80dB) . . . . . . 5
428H4EX
8-pole, 6 zero elliptic, 1.56 (-80dB) . . . . . . 5
428H4EY
8-pole, 6 zero elliptic, 2.00 (-100dB) . . . . . 5
General Specifications:
Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . 6
Pin-out/package data. . . . . . . . . . . . . . . . . . . . . . . . . 6
32-Pin DIP
8-Pole Filters
25 Locust St, Haverhill, Massachusetts 01830 • Tel: 800/252-7074, 978/374-0761 • FAX: 978/521-1839
e-mail: sales@freqdev.com • Web Address: http://www.freqdev.com
428 Series
4-Bit Programmable Filters
Digital Tuning Characteristics
The digital tuning interface circuits are a parallel set of CMOS
switches which accept CMOS compatible inputs for the four
tuning bits (D
0
- D
3
).
Digital Tuning &
Control Characteristics
Pin-Out Key
IN
Analog Input Signal
D
3
D
2
Tuning Bit 3 (MSB)
Tuning Bit 2
Tuning Bit 1
Tuning Bit 0 (LSB)
OUT Analog Output Signal
GND Power and Signal Return D
1
Binary Tuning Range
MSB
2
3
D
3
0
0
0
0
1
---
2
2
D
2
0
0
0
1
1
---
2
1
D
1
0
0
1
1
1
LSB
2
0
D
0
0
1
1
1
1
Bit
Weight
fc - corner
frequency
f
max
/16
f
max
/8
f
max
/4
f
max
/2
f
max
+Vs
-Vs
Os
Supply Voltage, Positive
D
0
Supply Voltage, Negative +5V Logic Power
Offset Adjustment
0.80
0.70
Out
Bottom View
Gnd Os
4
-Vs +Vs
D1
+5V
D2 D3
In
Binary Tuning Equation:
fc = (f
max
/16) [1+ D
3
x 2
3
+ D
2
x 2
2
+ D
1
x 2
1
+ D
0
x 2
0
]
where D
1
- D
3
= “0” or “1”, and
f
max
= Maximum tuning frequency
fc = Corner frequency;
Minimum tunable frequency = f
max
/16 (D
0
thru D
3
= 0);
Minimum frequency step (Resolution) = f
max
/16
D0
0.10
0.00
0.80
0.90
1.00
1.10
0.00
Discrete Frequencies
F
F
B
F
1
F
2
F
3
F
4
D
0
0
1
1
1
1
D
1
0
0
1
1
1
D
2
0
0
0
1
1
D
3
0
0
0
0
1
Data Input Specifications
Input Data Levels
Input Voltage (
Vs=15 Vdc
)
Low Level In
High Level In
Input Current
High Level In
Low Level In
Input Capacitance
Input Data Format
Positive Logic
(+5Vdc CMOS Logic)
0 Vdc min.
3.5 Vdc min.
0.5 Vdc max.
5.0 Vdc max.
Discrete Tuning Equation:
fc = F
B
+ D
0
[∆f
0
] + D
1
[∆f
1
] + D
2
[∆f
2
] + D
3
[∆f
3
]
∆f
0
,
∆f
1
,
∆f
2
,
∆f
3
are the incremental frequency shifts for the data
bits D
0
, D
1
,
D
2
and D
3
. They are selected to realize the five
customer specified programming frequencies F
B
⇒
F
4
. Other
programming codes produce valid fc’s between F
B
and F
4
.
-0.4µA typ.
+0.4µA typ.
20 pF typ.
-2.0µA max.
+2.0µA max.
30 pF max.
Frequency Select Bits
Logic “1” = (+5Vdc)
Logic “0” = Gnd
(Binary-Coded)
LSB (least significant bit)
MSB (most significant bit)
Bit Weight
D
0
D
3
Frequency Range16:1 Binary Weighted
2
25 Locust St, Haverhill, Massachusetts 01830 • Tel: 800/252-7074, 978/374-0761 • FAX: 978/521-1839
e-mail: sales@freqdev.com • Web Address: http://www.freqdev.com
1.50
1.60
1.30
1.80
0.30
0.50
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