Analog Devices DC2837A-A, Demo Manual

Page: 7 / 8

The following design example will show how to build
a unity-gain, 100Hz ƒ
–3dB
second-order filter using
DC2837A-A or DC2837A. The target specifications for
both a Bessel and a Butterworth filter with this architec-
ture are provided in Table 2.
Table 2. Target Second-Order Butterworth and Bessel
Filter Parameters
BUTTERWORTH BESSEL
k 1 1.274
Q 0.707 0.577
Populate the board with the component values in Table 3,
according to the following instructions and Figure 8.
Table 3. Sample A
V
= 1, ƒ
0
= 100Hz Filter Component Values
BUTTERWORTH BESSEL
R1 681k 806k
R2 169k 88.7k
Z1 681k 806k
C1 10nF 10nF
C2 2.2nF 2.2nF
Figure 8. Building A Second-Order Active Lowpass
Filter with DC2837A
1. Stuff Z6 with 0Ω to tie +IN to GND
2. Remove C11 and R5
3. Stuff C1, leave
JP2 connected
OUT
1 3
–IN
JP6
C10
0.1µF
R2 R1
R8
1k
R6
0Ω
R7
49.9Ω
C1
Z1
JP5
JP2
JP1
R5
C(R5)
Z6
0Ω
V
+
2
V
–
ENABLED
DC2837A-B F08
S
4. Replace R1 and R2 with desired values
5. Replace R5 with desired
capacitor C2 value
6. Stuff Z1 with desired value (gain set resistor).
7. Completely remove both jumper connectors from JP1
and JP5 (leave open)
8. Connect center pin 2 of JP1 to pin 2 of JP5
7
DEMO MANUAL
DC2837A-A/DC2837A-B
Rev. 0
OPERATING PRINCIPLES