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8-Bit Programmable Filters
828 Series
Digital Tuning &
Control Characteristics
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e-mail: sales@freqdev.com • Web Address: http://www.freqdev.com
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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 (D0 - D7).
Filter tuning follows the tuning equation given below:
fc = ( fmax/256 ) [ 1 + D7 x 2
7
+ D6 x 2
6
+ D5 x 2
5
+ D4 x 2
4
+
D3 x 2
3
+ D2 x 2
2
+ D1 x 2
1
+ D0 x 2
0
]
where D1 - D7 = "0" or "1", and
fmax = Maximum tuning frequency;
fc = corner frequency;
Minimum tunable frequency = fmax/256 (D0 thru D7 = 0);
Minimum frequency step (Resolution) = fmax/256
Data Input Specifications
Input Data Levels
(CMOS Logic)
Input Voltage (Vs = 15 Vdc)
Low Level In
0 Vdc min.
4 Vdc max.
High Level In
11 Vdc min.
15 Vdc max.
Input Current
High Level In
- 10
-5 µA typ.
-1
µA max..
Low Level In
+10
-5 µA typ.
+1
µA 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
(Binary-Coded)
D0
LSB (least significant bit)
D7
MSB (most significant bit)
Frequency Range
256 : 1, Binary Weighted
Pin-Out Key
IN
Analog Input Signal
D7 Tuning Bit 7 (MSB)
OUT Analog Output Signal
D6 Tuning Bit 6
GND Power and Signal Return
D5 Tuning Bit 5
+Vs
Supply Voltage, Positive
D4 Tuning Bit 4
-Vs
Supply Voltage, Negative
D3 Tuning Bit 3
Os
Offset Adjustment
D2 Tuning Bit 2
D1 Tuning Bit 1
D0 Tuning Bit 0 (LSB)
MSB
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LSB
Bit
Weight
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
fc
Corner
Frequency
D7
D6
D5
D4
D3
D2
D1
D0
00000000
fmax/256
00000001
fmax/128
00000011
fmax/64
00000111
fmax/32
00001111
fmax/16
00011111
fmax/8
00111111
fmax/4
01111111
fmax/2
11111111
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