MAX7490CEE+T Maxim Integrated Products, MAX7490CEE+T Datasheet - Page 11

• Manufacturer Part Number: MAX7490CEE+T
• Description: IC FILTER SW CAP DUAL 16-QSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX7490CEE+T

• Filter Type: Universal Switched Capacitor
• Frequency - Cutoff Or Center: 40kHz
• Number Of Filters: 2
• Max-order: 2nd
• Voltage - Supply: 4.5 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 2 shows the MAX7490/MAX7491s’ configuration
of Mode 1. This mode provides 2nd-order notch, low-
pass, and bandpass filter functions. The gain at all
three outputs is inversely proportional to the value of
R1. The center frequency, f
Q bandpass filters can be built without exceeding the
bandpass amplifier’s output swing (i.e., H
have to track Q). The notch and bandpass center fre-
quencies are identical. The notch output gain is the
same above and below the notch center frequency.
Mode 1 can also be used to make high-order Butter-
worth lowpass filters, low Q notches, and multiple-order
bandpass filters obtained by cascading identical
switched-capacitor sections.
Mode 1 Design Equations
Figure 2. Mode 1, 2nd-Order Filter Providing Notch, Bandpass,
and Lowpass Outputs
V
IN
R1
COM
f
f
Q
H
H
H
H
O
notch
Dual Universal Switched-Capacitor Filters
OLP
OBP
ON
ON
R3
R2
=
=
1
R
R
2
______________________________________________________________________________________
f
100
(
CLK
3
2
(
as f
=
=
=
at f
f
−
−
O
R
R
R
R
→
1
=
N
1
2
3
f
CLK
0
C
+
C
O
Hz
, is fixed at f
Σ
)
S
-
/ )
=
2
−
R
=
R
1
2
−
∫
R
R
1
2
CLK
OBP
BP
/100. High-
∫
does not
Mode 1
LP
Figure 3 shows the configuration of Mode 1B. R5 and
R6 are added to lower the feedback voltage from the
lowpass output to the summing input. This allows the
clock-to-center frequency to be adjusted beyond the
nominal value. This mode essentially has the same
functions and speed as Mode 1 while providing a high-
Q with f
Mode 1B Design Equations
Figure 4 shows the configuration of Mode 2. Mode 2 is
a combination of Mode 1 and Mode 3. In this mode,
f
However, it provides less sensitivity to resistor toler-
ances than does Mode 3. It has a highpass notch out-
put where the notch frequency depends solely on the
clock frequency.
Figure 3. Mode 1B, 2nd-Order Filter Providing Notch, Bandpass,
and Lowpass Outputs
CLK
V
IN
/f
O
CLK
R1
is always less than the part’s nominal ratio.
COM
/f
O
f
f
Q
H
H
H
H
O
n
ratios greater than the nominal value.
OLP
OBP
ON
ON
R3
R2
=
=
=
1
R
R
2
f
f
O
COM
100
(
CLK
3
2
(
as f
=
at f
=
−
−
R
R
R
R
R
N
1
→
=
R6
1
6
2
3
R
R
f
C
+
+
CLK
R
C
0
6
6
R
Hz
6
R
Σ
+
R
5
S
6
+
-
6
)
R
/ )
R
=
5
2
5
−
R5
=
R
R
∫
1
2
−
R
R
1
2
BP
∫
Mode 1B
Mode 2
LP
11