19-4526; Rev 4; 4/09
8th-Order, Lowpass,
Switched-Capacitor Filters
General Description
The MAX291/MAX292/MAX295/MAX296 are easy-to-use,
8th-order, lowpass, switched-capacitor filters that can be
set up with corner frequencies from 0.1Hz to 25kHz
(MAX291/MAX292) or 0.1Hz to 50kHz (MAX295/MAX296).
The MAX291/MAX295 Butterworth filters provide maxi-
mally flat passband response, and the MAX292/MAX296
Bessel filters provide low overshoot and fast settling. All
four filters have fixed responses, so the design task is
limited to selecting the clock frequency that controls the
filter’s corner frequency.
An external capacitor is used to generate a clock using
the internal oscillator, or an external clock signal can be
used. An uncommitted operational amplifier (noninverting
input grounded) is provided for building a continuous-
time lowpass filter for post-filtering or anti-aliasing.
Produced in an 8-pin DIP/SO and a 16-pin wide SO
package, and requiring a minimum of external compo-
nents, the MAX291 series delivers very aggressive per-
formance from a tiny area.
Features
o
8th-Order Lowpass Filters:
Butterworth (MAX291/MAX295)
Bessel
(MAX292/MAX296)
o
Clock-Tunable Corner-Frequency Range:
0.1Hz to 25kHz (MAX291/MAX292)
0.1Hz to 50kHz (MAX295/MAX296)
o
No External Resistors or Capacitors Required
o
Internal or External Clock
o
Clock to Corner Frequency Ratio:
100:1 (MAX291/MAX292)
50:1 (MAX295/MAX296)
o
Low Noise: -70dB THD + Noise (Typ)
o
Operate with a Single +5V Supply or
Dual ±5V Supplies
o
Uncommitted Op Amp for Anti-Aliasing or Clock-
Noise Filtering
o
8-Pin DIP and SO Packages
MAX291/MAX292/MAX295/MAX296
Applications
ADC Anti-Aliasing Filter
Noise Analysis
DAC Post-Filtering
50Hz/60Hz Line-Noise Filtering
PART
MAX291CPA
MAX291CSA
MAX291CWE
MAX291C/D
MAX291EPA
MAX291ESA
MAX291EWE
MAX291MJA
Ordering Information
TEMP. RANGE
0°C to +70°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
PIN-PACKAGE
8 Plastic DIP
8 SO
16 Wide SO
Dice*
8 Plastic DIP
8 SO
16 Wide SO
8 CERDIP**
Typical Operating Circuit
+5V
Ordering Information continued on last page.
* Contact factory for dice specifications.
** Contact factory for availability and processing to MIL-STD-883.
7
INPUT
8
V+
IN
OUT
OP OUT
5
3
CLK
1
4
V-
2
OP OUT
3
OP IN-
4
OUTPUT
Pin Configurations
TOP VIEW
8
IN
V+
GND
OUT
MAX29_
CLOCK
1
CLK
6
V-
2
OP IN-
MAX29_
7
6
5
-5V
Pin Configuration is 8-pin DIP/SO.
DIP/SO
16-pin Wide SO on last page.
1
________________________________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
8th-Order, Lowpass,
Switched-Capacitor Filters
MAX291/MAX292/MAX295/MAX296
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (V+ to V-).......................................................12V
Input Voltage at Any Pin.............V- + (-0.3V)
≤
V
IN
≤
V+ + (0.3V)
Continuous Power Dissipation
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) ...727mW
8-Pin SO (derate 5.88mW/°C above +70°C)................471mW
16-Pin Wide SO (derate 9.52mW/°C above +70°C) ....762mW
8-Pin CERDIP (derate 8.00mW/°C above +70°C)........640mW
Operating Temperature Ranges
MAX29_C_ _ ........................................................0°C to +70°C
MAX29_E_ _ .....................................................-40°C to +85°C
MAX29_MJA ..................................................-55°C to +125°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10s) .................................+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
(V+ = 5V, V- = -5V, filter output measured at OUT pin, 20kΩ load resistor to ground at OUT and OP OUT, f
CLK
= 100kHz
(MAX291/MAX292) or f
CLK
= 50kHz (MAX295/MAX296), T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
FILTER CHARACTERISTICS
Corner-Frequency Range
Clock to Corner
Frequency Ratio
Clock to Corner
Frequency Tempco
MAX291/MAX292
MAX295/MAX296
MAX291/MAX292
MAX295/MAX296
MAX291
MAX292
MAX295
MAX296
f
IN
= 0.50 F
o
MAX291
f
IN
= 1.00 F
o
f
IN
= 2.00 F
o
f
IN
= 3.00 F
o
f
IN
= 0.25 F
o
f
IN
= 0.50 F
o
f
IN
= 1.00 F
o
MAX292
f
IN
= 2.00 F
o
f
IN
= 3.00 F
o
f
IN
= 4.00 F
o
Insertion Gain Relative to
DC Gain
MAX295
f
IN
= 6.00 F
o
f
IN
= 0.50 F
o
f
IN
= 1.00 F
o
f
IN
= 2.00 F
o
f
IN
= 3.00 F
o
f
IN
= 0.25 F
o
f
IN
= 0.50 F
o
f
IN
= 1.00 F
o
MAX296
f
IN
= 2.00 F
o
f
IN
= 3.00 F
o
f
IN
= 4.00 F
o
f
IN
= 6.00 F
o
2
-2.2
-43.0
-70.0
-0.1
-0.6
-2.7
-11.0
-30.0
-47.0
-74.0
-2.2
-43.0
-70.0
-0.1
-0.6
-2.7
-11.0
-30.0
-47.0
-74.0
0.1-25k
0.1-50k
100:1
50:1
10
40
5
60
-0.02
-2.7
-48.0
-76.0
-0.2
-0.8
-3.0
-13.0
-34.0
-51.0
-78.0
-0.02
-2.7
-48.0
-76.0
-0.2
-0.8
-3.0
-13.0
-34.0
-51.0
-78.0
-0.3
-1.0
-3.3
-15.0
-0.1
-3.2
dB
-0.3
-1.0
-3.3
-15.0
-0.1
-3.2
Hz
CONDITIONS
MIN
TYP
MAX
UNITS
ppm/°C
_______________________________________________________________________________________
8th-Order, Lowpass,
Switched-Capacitor Filters
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 5V, V- = -5V, filter output measured at OUT pin, 20kΩ load resistor to ground at OUT and OP OUT, f
CLK
= 100kHz
(MAX291/MAX292) or f
CLK
= 50kHz (MAX295/MAX296), T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
Output DC Swing
Output Offset Voltage
DC Insertion Gain Error with
Output Offset Removed
Total Harmonic Distortion
plus Noise
Clock Feedthrough
CLOCK
Internal Oscillator
Frequency
Internal Oscillator
Current Source/Sink
Clock Input High
(Note 1)
Low
UNCOMMITTED OP AMP
Input Offset Voltage
Output DC Swing
Input Bias Current
POWER REQUIREMENTS
Supply Voltage
Dual Supply
Single Supply
Supply Current
V- = 0V, GND = V±2
V+ = 5V, V- = -5V, V
CLK
= 0V to 5V
V+ = 2.375V, V- = -2.375V, V
CLK
= -2V to 2V
±2.375
4.750
15
7
±5.500
11.000
22
12
V
V
mA
C
OSC
= 1000pF
V
CLK
= 0V or 5V
4.0
1.0
±10
±4
0.05
±50
29
35
±70
43
±120
kHz
µA
V
V
mV
V
µA
T
A
= +25°C, f
CLK
= 100kHz
f
CLK
= 100kHz
IN = GND
0.15
CONDITIONS
MIN
±4
±150
0
-70
6
±400
-0.15
TYP
MAX
UNITS
V
mV
dB
dB
mVp-p
MAX291/MAX292/MAX295/MAX296
Note 1.
Guaranteed by design.
Typical Operating Characteristics
(V+ = 5V, V- = -5V, T
A
= +25°C, f
CLK
= 100kHz (MAX291/MAX292) or f
CLK
= 50kHz (MAX295/MAX296), unless otherwise noted.)
INTERNAL OSCILLATOR PERIOD vs.
CAPACITANCE VALUE
MAX291/2/5/6-01
NORMALIZED INTERNAL OSCILLATOR
FREQUENCY vs. SUPPLY VOLTAGE
MAX291/2/5/6-02
NORMALIZED INTERNAL OSCILLATOR
FREQUENCY vs. TEMPERATURE
NORMALIZED OSCILLATOR FREQUENCY
1nF EXTERNAL
CAPACITOR CLK
1.06
MAX291/2/5/6-03
500
450
OSCILLATOR PERIOD (µs)
400
350
300
250
200
150
100
50
0
0
2
4
6
8
10
12
14
16
NORMALIZED OSCILLATOR FREQUENCY
1nF EXTERNAL
CAPACITOR CLK
1.030
1.020
1.03
1.00
1.010
1.000
0.990
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
0.97
0.94
-60 -40 -20
0
20
40 60
80 100 120 140
18
CAPACITANCE (nF)
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
_______________________________________________________________________________________
3
8th-Order, Lowpass,
Switched-Capacitor Filters
MAX291/MAX292/MAX295/MAX296
Typical Operating Characteristics (continued)
(V+ = 5V, V- = -5V, T
A
= +25°C, f
CLK
= 100kHz (MAX291/MAX292) or f
CLK
= 50kHz (MAX295/MAX296), unless otherwise noted.)
MAX291/MAX295
FREQUENCY RESPONSE
MAX291/2/5/6-04
MAX291/MAX295
FREQUENCY RESPONSE
MAX291/2/5/6-05
MAX292/MAX296
FREQUENCY RESPONSE
0
-20
GAIN (dB)
-40
-60
-80
-100
MAX292
-120
MAX296
F
o
= 1kHz
MAX291/2/5/6-06
0
-0.1
-0.2
GAIN (dB)
-0.3
-0.4
-0.5
-0.6
-0.7
0
200
400
600
800
F
o
= 1kHz
MAX291
MAX295
20
0
-20
GAIN (dB)
-40
-60
-80
-100
-120
MAX295
MAX291
F
o
= 1kHz
20
1k
0
1
2
3
4
5
0
2
4
6
8
10
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX291/2/5/6-07
MAX291/MAX295
FREQUENCY RESPONSE
MAX291/2/5/6-08
MAX292/MAX296
FREQUENCY RESPONSE
F
o
= 1kHz
-2
-4
MAX296
MAX292
MAX291/2/5/6-09
16
15
SUPPLY CURRENT I+ OR I- I(mA)
14
13
100kHz EXTERNAL CLOCK
0
-10
-20
GAIN (dB)
MAX291/MAX295
-40
-50
-60
-70
F
o
= 1kHz
0
11
10
9
8
7
6
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
GAIN (dB)
1.6k
2k
12
-30
-6
-8
-10
-12
-14
0
400
800
1.2k
0
400
800
1.2k
1.6k
2k
SUPPLY VOLTAGE, V+ OR |V-|
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
SUPPLY CURRENT vs. TEMPERATURE
MAX291/2/5/6-10
MAX291/MAX295
PHASE RESPONSE
MAX291/2/5/6-11
MAX292/296 PHASE RESPONSE
F
o
= 1kHz
-50
PHASE SHIFT (Degrees)
-100
-150
-200
-250
-300
f
o
= 1kHz
MAX291/2/5/6-12
16
15
SUPPLY CURRENT (mA)
14
13
12
11
100kHz EXTERNAL CLOCK
I+ OR | I- |
0
-80
PHASE SHIFT (Degrees)
-160
-240
-320
-400
-480
-560
MAX295
0
400
800
1.2k
1.6k
MAX291
0
-350
0
400
800
1.2k
1.6k
2k
10
-60 -40 -20 0
20 40 60 80 100 120 140
2k
TEMPERATURE (°C)
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
4
_______________________________________________________________________________________
8th-Order, Lowpass,
Switched-Capacitor Filters
Typical Operating Characteristics (continued)
(V+ = 5V, V- = -5V, R
LOAD
= 5kΩ, T
A
= +25°C, unless otherwise noted.)
MAX296 LOW-VOLTAGE
FREQUENCY RESPONSE
MAX291/2/5/6-13
MAX291/MAX292/MAX295/MAX296
MAX291 LOW-VOLTAGE
FREQUENCY RESPONSE
MAX291/2/5/6-14
MAX291 THD + NOISE vs.
INPUT SIGNAL AMPLITUDE
-45
-50
THD + NOISE (dB)
-55
-60
A
-65
-70
-75
-80
B
1
2
3
4
5
6
7
8
9
10
A: f
CLK
= 200kHz F
o
= 2kHz
INPUT FREQ. = 200Hz
MEAS. BANDWIDTH = 30kHz
B: f
CLK
= 1MHz F
o
= 1kHz
INPUT FREQ. = 1kHz
MEAS. BANDWIDTH = 80kHz
MAX291/2/5/6-15
0
-4
-8
GAIN (dB)
V+ = +2.5V
V- = -2.5V
-40
0
-4
GAIN (dB)
-8
-12
V+ = +2.5V
V- = -2.5V
F
C
= 20kHz
F
C
= 2kHz
-12
-16
-20
-24
-28
F
C
= 1kHz
F
C
= 20kHz
-16
-20
-24
-28
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
INPUT FREQUENCY (F/FC)
1.0
1.1
1.2
1.3
1.4
1.5
INPUT FREQUENCY (F/FC)
AMPLITUDE (Vp-p)
MAX296 LOW-VOLTAGE PHASE RESPONSE
MAX291/2/5/6-16
MAX291 LOW-FREQUENCY
PHASE RESPONSE
MAX291/2/5/6-17
MAX292 THD + NOISE vs.
INPUT SIGNAL AMPLITUDE
-45
-50
THD + NOISE (dB)
-55
-60
-65
-70
-75
-80
A
1
2
3
4
5
6
7
8
9
10
B
A: f
CLK
= 200kHz F
o
= 2kHz
INPUT FREQ. = 200Hz
MEAS. BANDWIDTH = 30kHz
B: f
CLK
= 1MHz F
o
= 1kHz
INPUT FREQ. = 1kHz
MEAS. BANDWIDTH = 80kHz
MAX291/2/5/6-18
-40
0
PHASE SHIFT (Degrees)
-90
-180
-270
-360
-450
-540
-630
0
V+ = +2.5V
V- = -2.5V
0
PHASE SHIFT (Degrees)
-80
-160
-240
-320
-400
-480
-560
F
C
= 1kHz
V+ = +2.5V
V- = -2.5V
F
C
= 20kHz
F
C
= 2kHz
F
C
= 20kHz
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
INPUT FREQUENCY (F/FC)
1.0
1.1
1.2
1.3
1.4
1.5
INPUT FREQUENCY (F/FC)
AMPLITUDE (Vp-p)
MAX295 THD + NOISE vs.
INPUT SIGNAL AMPLITUDE
MAX291/2/5/6-19
MAX296 THD + NOISE vs.
INPUT SIGNAL AMPLITUDE
-45
-50
THD + NOISE (dB)
-55
-60
-65
-70
-75
D
C: f
CLK
= 200kHz F
o
= 4kHz
INPUT FREQ. = 400Hz
MEAS. BANDWIDTH = 30kHz
D: f
CLK
= 1MHz F
o
= 20kHz
INPUT FREQ. = 2kHz
MEAS. BANDWIDTH = 80kHz
MAX291/2/5/6-20
-40
-45
-50
THD + NOISE (dB)
-55
-60
-65
-70
-75
-80
1
C: f
CLK
= 200kHz F
o
= 4kHz
INPUT FREQ. = 400Hz
MEAS. BANDWIDTH = 30kHz
D: f
CLK
= 1MHz F
o
= 20kHz
INPUT FREQ. = 2kHz
MEAS. BANDWIDTH = 80kHz
-40
D
C
2
3
4
5
6
7
8
9
10
AMPLITUDE (Vp-p)
-80
1
C
2
3
4
5
6
7
8
9
10
AMPLITUDE (Vp-p)
_______________________________________________________________________________________
5
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