Datasheet

MAX260/MAX261/MAX262
Microprocessor Programmable
Universal Active Filters
8 _______________________________________________________________________________________
Step 1—Filter Design
Start with the program “PZ” to determine what type of
filter is needed. This helps determine the type
(Butterworth, Chebyshev, etc.) and the number of poles
for the optimum choice. The program also plots the fre-
quency response and calculates the pole/zero (f
0
) and
Q values for each second-order section. Each
MAX260/MAX261/MAX262 contains two second-order
sections, and devices can be cascaded for higher
order filters.
MAX260
MAX261*
MAX262*
IN
A
OUT
IN
5
24
3
1
23
22
(20)14
21
LP
A
HP
A
BP
A
LP
B
HP
B
BP
B
IN
B
WR
D0
D1
A0
A2
A3
CLK
A
CLK
B
A1
16(15)
20(19)
6
1
2
3
4
5
6
7
11
24
25
23
22
21
20
19
18
DB-25 MALE PLUG
(BACK VIEW)
12
15(14)
10
7
11
12
9 18(17) 17(16)
CLK IN
TTL
(SEE FIGURE 4)
0.1µF 0.1µF
-5V+5V
13
V
+
V
-
GND
*PIN NUMBERS IN ( ) ARE FOR MAX261/MAX262
100 AB$ = "FILTER A" : GOSUB 150 : REM GET DATA FOR SECTION A
110 ADD = 0 : GOSUB 220 : REM WRITE DATA TO THE PRINTER PORT
120 AB$ = "FILTER B" : GOSUB 150 : REM GET DATA FOR B
130 ADD = 32 : GOSUB 220 : REM WRITE DATA TO PRINTER PORT
140 GOTO 100
150 PRINT "MODE (1 to 4, see Table 5) "; AB$; : INPUT M
160 IF M<1 OR M>4 THEN GOTO 150
170 PRINT "CLOCK RATIO (0 to 63, N of Table 2) "; AB$; : INPUT F
180 IF F<0 OR F>63 THEN GOTO 170
190 PRINT "Q (0 to 127, N of Table 3) "; AB$; : INPUT Q
200 IF Q<0 OR Q>127 THEN GOTO 190 ELSE : PRINT
210 RETURN
220 LPRINT CHR$(ADD+M-1); : ADD = ADD+4
230 FOR I = 1 TO 3
240 X = (ADD + (F - 4*INT(F/4))) : LPRINT CHR$(X);
250 F=INT(F/4) : ADD = ADD + 4
260 NEXT I
270 FOR I = 1 TO 4
280 X=(ADD + (Q - 4*INT(Q/4))) : LPRINT CHR$(X);
290 Q=I
(Q/4) :: ADD = ADD + 4
300 NEXT I
310 RETURN
Figure 2. Basic Program and Hardware Connections to Parallel Printer Port for “Quick Look” Using a PC