8-Bit Programmable Filters
828 Series
Digital Tuning &
Control Characteristics
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
2
Digital Tuning Characteristics
The digital tuning interface circuits are a parallel set of eight
(8) 4053 CMOS switches which accept CMOS compatible
inputs for the eight tuning bits (D
0
- D
7
).
Filter tuning follows the tuning equation given below:
f
c
= ( f
max
/256 ) [ 1 + D
7
x 2
D
3
x 2
7
+ D
6
x 2
1
+ D
0
x 2
6
+ D
5
x 2
0
]
5
+ D
4
x 2
4
+
3
+ D
2
x 2
2
+ D
1
x 2
where D
1
- D
7
= "0" or "1", and
f
max
= Maximum tuning frequency;
f
c
= corner frequency;
Minimum tunable frequency = f
max
/256 (D
0
thru D
7
= 0);
Minimum frequency step (Resolution) = f
max
/256
Data Input Specifications
Input Data Levels
(CMOS Logic)
Input Voltage (Vs = 15 Vdc)
Low Level In
High Level In
0 Vdc min.
11 Vdc min.
4 Vdc max.
15 Vdc max.
Input Current
High Level In
Low Level In
- 10
+10
-5
μ
A typ.
-5
μ
A typ
.
-1
μ
A max.
.
+1
μ
A max.
Input Capacitance
5 pF typ
7.5 pF max.
Input Data Format
Frequency Select Bits
Positive Logic
Logic "1" = +Vs
Logic "0" = Gnd
Bit Weighting
D
0
D
7
(Binary-Coded)
LSB (least significant bit)
MSB (most significant bit)
Frequency Range
256 : 1, Binary Weighted
Pin-Out Key
IN
OUT Analog Output Signal
GND Power and Signal Return
+Vs
Supply Voltage, Positive
-Vs
Supply Voltage, Negative
Os
Offset Adjustment
Analog Input Signal
D
7
Tuning Bit 7 (MSB)
D
6
Tuning Bit 6
D
5
Tuning Bit 5
D
4
Tuning Bit 4
D
3
Tuning Bit 3
D
2
Tuning Bit 2
D
1
Tuning Bit 1
D
0
Tuning Bit 0 (LSB)
MSB
---
---
---
---
---
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LSB
Bit
Weight
Corner
Frequency
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
D
7
D
6
D
5
D
4
D
3
D
2
D
1
D
0
0
0
0
0
0
0
0
0
f
max
/256
0
0
0
0
0
0
0
1
f
max
/128
0
0
0
0
0
0
1
1
f
max
/64
0
0
0
0
0
1
1
1
f
max
/32
0
0
0
0
1
1
1
1
f
max
/16
0
0
0
1
1
1
1
1
f
max
/8
0
0
1
1
1
1
1
1
f
max
/4
0
1
1
1
1
1
1
1
f
max
/2
1
1
1
1
1
1
1
1
fmax
+Vs
OUT
-Vs
D
D
D
D
GND
D
D
D
D
IN
2.00
Bottom View
Os
4
5
3
2
1
0
6
7
4