MAX260ACNG Maxim Integrated Products, MAX260ACNG Datasheet - Page 17

• 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

Figure 8. Filter Mode 2: Second-Order Bandpass, Lowpass,
and Notch
Figure 9. Filter Mode 3: Second-Order Bandpass, Lowpass,
and Highpass
Mode 1, along with mode 4, supports the highest clock
frequencies (see Table 1) because the input summing
amplifier is outside the filter’s resonant loop (Figure 7).
The gain of the lowpass and notch outputs is 1, while
the bandpass gain at the center frequency is Q. For
bandpass gains other than Q, the filter input or output
can be scaled by a resistive divider or op amp.
MODE 2 (Figure 8) is used for all-pole lowpass and
bandpass filters. Key advantages compared to mode 1
are higher available Qs (see Table 3) and lower output
noise. Mode 2’s available f
with mode 1 (see Table 2), so a wider overall range of
f
modes are used together. This is demonstrated in the
Wide Passband Chebyshev Bandpass design example.
0
s can be selected from a single clock when both
IN
IN
SCN
SCN
SCN = SWITCHED-CAPACITOR NETWORK
SCN
SCN
SCN
SCN
+
______________________________________________________________________________________
-
+
-
CLK
+
+
MODE 3
MODE 2
HP
N
Σ
Σ
SCN
SCN
/f
0
-
-
-
-
ratios are √2 less than
∫
∫
Microprocessor Programmable
∫
∫
BP
LP
BP
LP
Universal Active Filters
MODE 3 (Figure 9) is the only mode that produces
high-pass filters. The maximum clock frequency is
somewhat less than with mode 1 (see Table 1).
MODE 3A (Figure 10) uses a separate op amp to sum
the highpass and lowpass outputs of mode 3, creating
a separate notch output. This output allows the notch to
be set independently of f
feedback resistor ratio (R
external resistors. Because the notch can be indepen-
dently set, mode 3A is also useful when designing
pole-zero filters such as elliptics.
MODE 4 (Figure 11) is the only mode that provides an
allpass output. This is useful when implementing group
delay equalization. In addition to this, mode 4 can also
be used in all pole lowpass and bandpass filters. Along
with mode 1, it is the fastest operating mode for the fil-
ter, although the gains are different than in mode 1.
When the allpass function is used, note that some
amplitude peaking occurs (approximately 0.3dB when
Q = 8) at f
highest in mode 4 (see Figure 20).
Figure 10. Filter Mode 3a: Second-Order Bandpass, Lowpass,
Highpass, and Notch. For elliptic LP, BP, HP, and Notch, the N
output is used.
IN
SCN
0
. Also note that f
SCN = SWITCHED-CAPACITOR NETWORK
SCN
SCN
-
+
MODE 3A
0
H
+
0
by adjusting the op amp’s
, R
HP
and Q sampling errors are
Σ
SCN
R
R
L
H
L
-
-
). R
∫
H
BP
, R
L
R
, and R
G
+
-
∫
G
N
LP
are
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