MAX260ACNG Maxim Integrated Products, MAX260ACNG Datasheet - Page 24

• Manufacturer Part Number: MAX260ACNG
• Description: Active Filter
• Manufacturer: Maxim Integrated Products

Specifications of MAX260ACNG

• Number Of Channels: 2
• Cutoff Frequency: 7.5 KHz
• Supply Voltage (max): 12.6 V
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Supply Voltage (min): 4.74 V
• Package / Case: PDIP N-24
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Microprocessor Programmable
Universal Active Filters
Figure 22. Fourth-Order Chebyshev Bandpass Filter
In Figure 23, a series of response curves are shown for
the previous configuration using a MAX261 with clock
frequencies ranging from 750kHz to 4MHz (f
500Hz to 30kHz). Note that the rightmost curve shows
about 2dB of gain peaking compared to the lower fre-
quency curves, indicating the upper limit of usable filter
accuracy at this Q (see Table 1).
In this example (Figure 24), the desired parameters
are:
Center frequency (f
Pass bandwidth
Stop bandwidth
Max passband ripple
Min stopband attenuation
24
CLK
150kHz
______________________________________________________________________________________
V
IN
A,B
Wide Passband Chebyshev Bandpass
-10
-35
-60
40
15
CLK
200
CLK
IN
MODE
A
A
5
11
1
500
0
N = 42
)
CLK
FREQUENCY (Hz)
BP
1K
f
OA
A
B
1
12
GAIN
PHASE
MAX260
2K
N = 23
f
= 1kHz
= 1kHz
= 3kHz
= 1dB
= 20dB
OB
IN
5K
B
23
WR, AX, DX
PROGRAM
10K
N = 119
Q
20K
A
BP
B
-180
-90
0
90
180
21
N = 119
V
Q
OUT
0
B
from
From the previous parameters, we use either lookup
tables, design texts, or Maxim's filter design programs
to generate the order (number of poles), and the f
Q of each second-order section. The A and B parame-
ters are:
f
Q
To implement this filter, section A operates in mode 1
and section B uses mode 2 to provide a wider overall
range of f
can drive both sections A and B. See Tables 2 and 3.
CLK
f
f
Q
83)
The overall passband gain at f
-3.9dB.
The same Chebyshev response shape shown in Figure
24 is implemented at higher frequencies with a
MAX262 in Figure 25. The curves show plots for center
frequencies of 15.6kHz, 31.3kHz, and 47kHz. Not only
is this faster than the MAX260 implementation, but
mode 1 can be used in both halves of the MAX262 for
this filter because the range of available f
wider with the MAX262 than the MAX260.
Figure 23. MAX261 Fourth-Order Chebyshev Bandpass Using
Coefficients of Figure 22
0A
CLK
CLK
A
A
= 639Hz
= 2.01
= 2.000 (Mode 1, N = 96), Q
/f
/f
A
0A
0B
= CLK
High-Frequency Chebyshev Bandpass
= 188.49 (Mode 1, N = 56), actual f
= 76.64 (Mode 2, N = 5), actual f
CLK
-15
-30
30
15
0
B
/f
1K
= 120kHz
0
ratios. This way, one clock frequency
2K
f
Q
0B
B
= 1564Hz
= 2.01
5K
FREQUENCY (Hz)
10K
B
20K
= 2.01 (Mode 2, N =
0
50K
is 0.64V/V or
0B
CLK
0A
100K
= 156.5Hz
= 636.6Hz
/f
0
ratios is
0
and