MAX7480ESA+ Maxim Integrated Products, MAX7480ESA+ Datasheet - Page 6

• Manufacturer Part Number: MAX7480ESA+
• Description: IC FILTER LOWPASS 8TH 8-SOIC
• Manufacturer: Maxim Integrated Products

Specifications of MAX7480ESA+

• Filter Type: Butterworth, Lowpass Switched Capacitor
• Frequency - Cutoff Or Center: 2kHz
• Number Of Filters: 4
• Max-order: 8th
• Voltage - Supply: 4.5 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Number Of Channels: Single
• Cutoff Frequency: 2 KHz
• Supply Voltage (max): 5 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Supply Voltage (min): 4.5 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX7480 Butterworth filter operates with a 100:1
clock-to-corner frequency ratio and a 2kHz maximum
corner frequency.
Lowpass Butterworth filters provide a maximally flat
passband response, making them ideal for instrumen-
tation applications that require minimum deviation from
the DC gain throughout the passband.
Figure 1 shows the difference between Bessel and
Butterworth filter frequency responses. With the filter
cutoff frequencies set at 1kHz, trace A shows the
Bessel filter response and trace B shows the
Butterworth filter response.
Most switched-capacitor filters (SCFs) are designed
with biquadratic sections. Each section implements two
filtering poles, and the sections are cascaded to pro-
duce higher-order filters. The advantage to this
approach is ease of design. However, this type of
design is highly sensitive to component variations if any
section’s Q is high. An alternative approach is to emu-
late a passive network using switched-capacitor inte-
grators with summing and scaling. Figure 2 shows a
basic 8th-order ladder filter structure.
A switched-capacitor filter such as the MAX7480 emu-
lates a passive ladder filter. The filter’s component sen-
sitivity is low when compared to a cascaded biquad
design, because each component affects the entire fil-
ter shape, not just one pole-zero pair. In other words, a
mismatched component in a biquad design will have a
concentrated error on its respective poles, while the
same mismatch in a ladder filter design results in an
error distributed over all poles.
8th-Order, Lowpass, Butterworth,
Switched-Capacitor Filter
6
_______________Detailed Description
PIN
_______________________________________________________________________________________
1
2
3
4
5
6
7
8
NAME
SHDN
COM
GND
OUT
CLK
V
OS
IN
DD
Common Input Pin. Biased internally at mid-supply. Bypass externally to GND with a 0.1µF capacitor. To
override internal biasing, drive with an external supply.
Filter Input
Ground
+5V Supply Input
Filter Output
Offset Adjust Input. To adjust output offset, bias OS externally. Connect OS to COM if no offset adjustment is
needed. Refer to
Shutdown Input. Drive low to enable shutdown mode; drive high or connect to V
Clock Input. To override the internal oscillator, connect to an external clock; otherwise, connect an external
capacitor (C
Background Information
OSC
) from CLK to GND to set the internal oscillator frequency.
Offset and Common-Mode Input Adjustment section.
Figure 2. 8th-Order Ladder Filter Network
Figure 1. Bessel vs. Butterworth Filter Frequency Response
FUNCTION
+
-
V
R1
IN
-100
-20
-40
-60
-80
20
A: BESSEL FILTER RESPONSE; f
B: BUTTERWORTH FILTER RESPONSE; f
0
L1
0.1
C2
0.2
L3
FREQUENCY (kHz)
C4
0.5
1
DD
C
L5
Pin Description
= 1kHz
B
for normal operation.
C6
2
C
= 1kHz
A
5
L7
C8
10
R2
V
0