19-4788; Rev 1; 6/99
8th-Order, Lowpass, Bessel,
Switched-Capacitor Filters
General Description
The MAX7401/MAX7405 8th-order, lowpass, Bessel,
switched-capacitor filters (SCFs) operate from a single
+5V (MAX7401) or +3V (MAX7405) supply. These
devices draw only 2mA of supply current and allow cor-
ner frequencies from 1Hz to 5kHz, making them ideal
for low-power post-DAC filtering and anti-aliasing appli-
cations. They feature a shutdown mode that reduces
supply current to 0.2µA.
Two clocking options are available on these devices:
self-clocking (through the use of an external capacitor)
or external clocking for tighter corner-frequency control.
An offset adjust pin allows for adjustment of the DC out-
put level.
The MAX7401/MAX7405 Bessel filters provide low over-
shoot and fast settling. Their fixed response simplifies
the design task to selecting a clock frequency.
o
8th-Order, Lowpass Bessel Filters
o
Low Noise and Distortion: -82dB THD + Noise
o
Clock-Tunable Corner Frequency (1Hz to 5kHz)
o
100:1 Clock-to-Corner Ratio
o
Single-Supply Operation
+5V (MAX7401)
+3V (MAX7405)
o
Low Power
2mA (Operating Mode)
0.2µA (Shutdown Mode)
o
Available in 8-Pin SO/DIP Packages
o
Low Output Offset:
±5mV
Features
MAX7401/MAX7405
Applications
ADC Anti-Aliasing
Post-DAC Filtering
Air-Bag Electronics
CT2 Base Stations
Speech Processing
PART
MAX7401CSA
MAX7401CPA
MAX7401ESA
MAX7401EPA
MAX7405CSA
MAX7405CPA
MAX7405ESA
MAX7405EPA
Ordering Information
TEMP. RANGE
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
8 SO
8 Plastic DIP
8 SO
8 Plastic DIP
8 SO
8 Plastic DIP
8 SO
8 Plastic DIP
Pin Configuration
TOP VIEW
COM
1
IN
2
GND
3
8
7
CLK
SHDN
OS
OUT
V
SUPPLY
0.1µF
V
DD
INPUT
IN
SHDN
OUT
OUTPUT
Typical Operating Circuit
MAX7401
MAX7405
6
5
V
DD
4
SO/DIP
MAX7401
MAX7405
CLOCK
CLK
GND
COM
OS
0.1µF
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
8th-Order, Lowpass, Bessel,
Switched-Capacitor Filters
MAX7401/MAX7405
ABSOLUTE MAXIMUM RATINGS
V
DD
to GND
MAX7401 ..............................................................-0.3V to +6V
MAX7405 ..............................................................-0.3V to +4V
IN, OUT, COM, OS, CLK ...........................-0.3V to (V
DD
+ 0.3V)
SHDN........................................................................-0.3V
to +6V
OUT Short-Circuit Duration...................................................1sec
Continuous Power Dissipation (T
A
= +70°C)
8-Pin SO (derate 5.88mW/°C above +70°C)................471mW
8-Pin DIP (derate 9.09mW/°C above +70°C) ...............727mW
Operating Temperature Ranges
MAX740 _C_A ....................................................0°C to +70°C
MAX740 _E_A .................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS—MAX7401
(V
DD
= +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF from COM to GND,
SHDN
= V
DD
, f
CLK
= 100kHz, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
FILTER CHARACTERISTICS
Corner Frequency
Clock-to-Corner Ratio
Clock-to-Corner Tempco
Output Voltage Range
Output Offset Voltage
DC Insertion Gain with
Output Offset Removed
Total Harmonic Distortion
plus Noise
OS Voltage Gain to OUT
Input Voltage Range at OS
THD+N
A
OS
V
OS
Input, COM externally driven
COM Voltage Range
V
COM
Output, COM internally biased
Input Resistance at COM
Clock Feedthrough
Resistive Output Load Drive
Maximum Capacitive Load at
OUT
Input Leakage Current at COM
Input Leakage Current at OS
CLOCK
Internal Oscillator Frequency
Clock Input Current
Clock Input High
Clock Input Low
f
OSC
I
CLK
V
IH
V
IL
C
OSC
= 1000pF (Note 4)
V
CLK
= 0 or 5V
V
DD
- 0.5
0.5
29
38
±15
48
±30
kHz
µA
V
V
R
L
C
L
SHDN
= GND, V
COM
= 0 to V
DD
V
OS
= 0 to (V
DD
- 1V) (Note 3)
10
50
R
COM
V
DD
/ 2
- 0.5
V
DD
/ 2
- 0.2
75
V
OFFSET
V
IN
= V
COM
= V
DD
/ 2
V
COM
= V
DD
/ 2 (Note 2)
f
IN
= 200Hz, V
IN
= 4Vp-p,
measurement bandwidth = 22kHz
-0.1
0.25
±5
0.15
-82
1
V
COM
±0.1
V
DD
/ 2
V
DD
/ 2
+ 0.5
V
V
DD
/ 2
V
DD
/ 2
+ 0.2
125
10
1
500
±0.1
±0.1
±10
±10
kΩ
mVp-p
kΩ
pF
µA
µA
f
C
f
CLK
/ f
C
(Note 1)
0.001 to 5
100:1
10
V
DD -
0.25
±25
0.3
ppm/°C
V
mV
dB
dB
V/ V
V
kHz
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
8th-Order, Lowpass, Bessel,
Switched-Capacitor Filters
ELECTRICAL CHARACTERISTICS—MAX7401 (continued)
(V
DD
= +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF from COM to GND,
SHDN
= V
DD
, f
CLK
= 100kHz, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
POWER REQUIREMENTS
Supply Voltage
Supply Current
Shutdown Current
Power-Supply Rejection Ratio
SHUTDOWN
SHDN
Input High
SHDN
Input Low
SHDN
Input Leakage Current
V
SDH
V
SDL
V
SHDN
= 0 to V
DD
±0.1
V
DD
- 0.5
0.5
±10
V
V
µA
V
DD
I
DD
I
SHDN
PSRR
Operating mode, no load, IN = OS = COM
SHDN
= GND, CLK driven from 0 to V
DD
Measured at DC
4.5
2
0.2
60
5.5
3.5
1
V
mA
µA
dB
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX7401/MAX7405
ELECTRICAL CHARACTERISTICS—MAX7405
(V
DD
= +3V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF from COM to GND,
SHDN
= V
DD
, f
CLK
= 100kHz, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
FILTER CHARACTERISTICS
Corner Frequency
Clock-to-Corner Ratio
Clock-to-Corner Tempco
Output Voltage Range
Output Offset Voltage
DC Insertion Gain with
Output Offset Removed
Total Harmonic Distortion
plus Noise
OS Voltage Gain to OUT
Input Voltage Range at OS
COM Voltage Range
Input Resistance at COM
Clock Feedthrough
Resistance Output Load Drive
Maximum Capacitive
Load at OUT
Input Leakage Current at COM
Input Leakage Current at OS
R
L
C
L
SHDN
= GND, V
COM
= 0 to V
DD
V
OS
= 0 to (V
DD
- 1V) (Note 3)
10
50
THD+N
A
OS
V
OS
V
COM
R
COM
COM internally biased or externally driven
V
DD
/ 2
- 0.1
75
V
OFFSET
V
IN
= V
COM
= V
DD
/ 2
V
COM
= V
DD
/ 2 (Note 2)
f
IN
= 200Hz, V
IN
= 2.5Vp-p,
measurement bandwidth = 22kHz
-0.1
0.25
±5
0.03
-84
1
V
COM
±0.1
V
DD
/ 2
125
10
1
500
±0.1
±0.1
±10
±10
V
DD
/ 2
+ 0.1
f
C
f
CLK/
f
C
(Note 1)
0.001 to 5
100:1
10
V
DD -
0.25
±25
0.3
ppm/°C
V
mV
dB
dB
V/ V
V
V
kΩ
mVp-p
kΩ
pF
µA
µA
kHz
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
_______________________________________________________________________________________
3
8th-Order, Lowpass, Bessel,
Switched-Capacitor Filters
MAX7401/MAX7405
ELECTRICAL CHARACTERISTICS—MAX7405 (continued)
(V
DD
= +3V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF from COM to GND,
SHDN
= V
DD
, f
CLK
= 100kHz, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
CLOCK
Internal Oscillator Frequency
Clock Input Current
Clock Input High
Clock Input Low
POWER REQUIREMENTS
Supply Voltage
Supply Current
Shutdown Current
Power-Supply Rejection Ratio
SHUTDOWN
SHDN
Input High
SHDN
Input Low
SHDN
Input Leakage Current
V
SDH
V
SDL
V
SHDN
= 0 to V
DD
±0.1
V
DD
- 0.5
0.5
±10
V
V
µA
V
DD
I
DD
I
SHDN
PSRR
Operating mode, no load, IN = OS = COM
SHDN
= GND, CLK driven from 0 to V
DD
Measured at DC
2.7
2
0.2
60
3.6
3.5
1
V
mA
µA
dB
f
OSC
I
CLK
V
IH
V
IL
C
OSC
= 1000pF (Note 4)
V
CLK
= 0 or 3V
V
DD
- 0.5
0.5
26
34
±15
43
±30
kHz
µA
V
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
FILTER CHARACTERISTICS—MAX7401/MAX7405
(V
DD
= +5V for MAX7401, V
DD
= +3V for MAX7405; filter output measured at OUT; 10kΩ
||
50pF load to GND at OUT;
SHDN
= V
DD
;
V
COM =
V
OS =
V
DD
/2; f
CLK
= 100kHz; T
A
= T
MIN
to T
MAX
; unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
f
IN
= 0.5f
C
Insertion Gain Relative to
DC Gain
f
IN
= f
C
f
IN
= 3f
C
f
IN
= 6f
C
CONDITIONS
MIN
-1.0
-3.3
TYP
-0.8
-3.0
-33
-79
MAX
-0.6
-2.7
-29
-74
dB
UNITS
Note 1:
The maximum f
C
is defined as the clock frequency, f
CLK
= 100
·
f
C,
at which the peak SINAD drops to 68dB with a sinu-
soidal input at 0.2f
C
.
Note 2:
DC insertion gain is defined as
∆V
OUT
/
∆V
IN
.
Note 3:
OS voltages above V
DD
- 1V saturate the input and result in a 75µA typical input leakage current.
Note 4:
For MAX7401, f
OSC
(kHz)
≅
38
·
10
3
/ C
OSC
(pF). For MAX7405, f
OSC
(kHz)
≅
34
·
10
3
/ C
OSC
(pF).
4
_______________________________________________________________________________________
8th-Order, Lowpass, Bessel,
Switched-Capacitor Filters
Typical Operating Characteristics
(V
DD
= +5V for MAX7401, V
DD
= +3V for MAX7405; f
CLK
= 100kHz;
SHDN
= V
DD
; V
COM
= V
OS
= V
DD
/ 2; T
A
= +25°C; unless otherwise
noted.)
FREQUENCY RESPONSE
MAX7401 toc01
MAX7401/MAX7405
PASSBAND FREQUENCY RESPONSE
MAX7409 toc02
PHASE RESPONSE
f
C
= 1kHz
-50
PHASE SHIFT (DEGREES)
-100
-150
-200
-250
-300
-350
-400
MAX7401 toc03
10
f
C
= 1kHz
0
-10
GAIN (dB)
0.5
f
C
= 1kHz
0
-0.5
GAIN (dB)
-1.0
-1.5
-2.0
-2.5
-3.0
0
-20
-30
-40
-50
-60
-70
0
1
2
3
4
5
INPUT FREQUENCY (kHz)
-3.5
0
202
404
606
808
1010
INPUT FREQUENCY (Hz)
0
400
800
1200
1600
2000
INPUT FREQUENCY (Hz)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX7401 toc04
SUPPLY CURRENT
vs. TEMPERATURE
MAX7401 toc05
OFFSET VOLTAGE
vs. SUPPLY VOLTAGE
V
IN
= V
COM
= V
DD
/ 2
15
OFFSET VOLTAGE (mV)
10
5
0
-5
-10
-15
-20
2.5
3.0
3.5
4.0
4.5
5.0
5.5
MAX7405
MAX7401
MAX7401 toc06
2.5
2.4
2.3
SUPPLY CURRENT (mA)
2.2
2.1
2.0
1.9
1.8
1.7
1.6
1.5
2.5
3.0
3.5
4.0
4.5
5.0
MAX7405
MAX7401
NO LOAD
2.03
NO LOAD
2.02
SUPPLY CURRENT (mA)
2.01
MAX7401
2.00
1.99
MAX7405
1.98
1.97
-40
-20
0
20
40
60
80
20
5.5
100
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
SUPPLY VOLTAGE (V)
OFFSET VOLTAGE vs. TEMPERATURE
MAX7401 toc07
INTERNAL OSCILLATOR FREQUENCY
vs. C
OSC
CAPACITANCE
MAX7401 toc08
NORMALIZED OSCILLATOR FREQUENCY
vs. SUPPLY VOLTAGE
NORMALIZED OSCILLATOR FREQUENCY
1.15
1.10
1.05
1.00
0.95
0.90
0.85
0.80
2.5
3.0
3.5
4.0
4.5
5.0
5.5
MAX7401
MAX7405
C
OSC
= 390pF
MAX7401 toc09
1.0
V
IN
= V
COM
= V
DD
/ 2
0.5
OFFSET VOLTAGE (mV)
10,000
OSCILLATOR FREQUENCY (kHz)
1.20
1000
0
100
-0.5
10
-1.0
1
-1.5
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
0.1
0.01
0.1
1
10
100
1000
C
OSC
CAPACITANCE (nF)
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5
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