AVAILABLE
Functional Diagrams
Pin Configurations appear at end of data sheet.
Functional Diagrams continued at end of data sheet.
UCSP is a trademark of Maxim Integrated Products, Inc.
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
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.
Applications
ADC Anti-Aliasing Filter
Noise Analysis
DAC Post-Filtering
50Hz/60Hz Line-Noise Filtering
Features
o8th-Order Lowpass Filters:
Butterworth (MAX291/MAX295)
Bessel (MAX292/MAX296)
oClock-Tunable Corner-Frequency Range:
0.1Hz to 25kHz (MAX291/MAX292)
0.1Hz to 50kHz (MAX295/MAX296)
oNo External Resistors or Capacitors Required
oInternal or External Clock
oClock to Corner Frequency Ratio:
100:1 (MAX291/MAX292)
50:1 (MAX295/MAX296)
oLow Noise: -70dB THD + Noise (Typ)
oOperate with a Single +5V Supply or
Dual ±5V Supplies
oUncommitted Op Amp for Anti-Aliasing or Clock-
Noise Filtering
o8-Pin DIP and SO Packages
8th-Order, Lowpass,
Switched-Capacitor Filters
Ordering Information
Pin Configurations
Ordering Information continued at end of data sheet.
* Contact factory for dice specifications.
** Contact factory for availability and processing to MIL-STD-883.
PART TEMP. RANGE PIN-PACKAGE
MAX291CPA
MAX291CWE
0°C to +70°C 8 Plastic DIP
MAX291C/D 0°C to +70°C
0°C to +70°C 16 Wide SO
Dice*
MAX291EPA -40°C to +85°C 8 Plastic DIP
MAX291EWE
MAX291MJA -55°C to +125°C
-40°C to +85°C 16 Wide SO
8 CERDIP**
GND
OP OUT
OUT
OP IN-
1
2
8
7
IN
V+
V-
CLK
MAX29_
DIP/SO
TOP VIEW
3
4
6
5
16-pin Wide SO at end of data sheet.
MAX291CSA 0°C to +70°C 8 SO
MAX291ESA -40°C to +85°C 8 SO
+5V
-5V
V+
V-
8
7
1
6
2
4
3
5
CLOCK CLK OP IN-
OP OUT
OUT OUTPUT
INPUT IN
MAX29_
Typical Operating Circuit
Pin Configuration is 8-pin DIP/SO.
19-4526; Rev 5; 5/10
MAX291/MAX292/
MAX295/MAX296
8th-Order, Lowpass,
Switched-Capacitor Filters
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V+ = 5V, V- = -5V, filter output measured at OUT pin, 20kΩload resistor to ground at OUT and OP OUT, fCLK = 100kHz
(MAX291/MAX292) or fCLK = 50kHz (MAX295/MAX296), TA= TMIN to TMAX, unless otherwise noted.)
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.
Supply Voltage (V+ to V-).......................................................12V
Input Voltage at Any Pin.............V- + (-0.3V) ≤VIN ≤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
Soldering Temperature (reflow) .......................................+240°C
MAX295/MAX296
MAX291/MAX292
MAX296
MAX295
MAX291/MAX292
MAX295/MAX296
MAX291
MAX292
CONDITIONS
Hz
0.1-50k
Corner-Frequency Range 0.1-25k
-0.02 -0.1
60
Clock to Corner
Frequency Tempco 5
100:1
50:1
Clock to Corner
Frequency Ratio
10
40
UNITSMIN TYP MAXPARAMETER
fIN = 0.50 Fo
fIN = 1.00 Fo-2.2 -2.7 -3.2
MAX291
fIN = 3.00 Fo-70.0 -76.0
fIN = 2.00 Fo-43.0 -48.0
fIN = 0.50 Fo-0.6 -0.8 -1.0
fIN = 2.00 Fo-11.0 -13.0 -15.0
fIN = 1.00 Fo-2.7 -3.0 -3.3
fIN = 0.25 Fo-0.1 -0.2 -0.3
fIN = 3.00 Fo-30.0 -34.0
MAX292
fIN = 6.00 Fo-74.0 -78.0
fIN = 4.00 Fo-47.0 -51.0
fIN = 1.00 Fo-2.2 -2.7 -3.2
MAX295
fIN = 3.00 Fo-70.0 -76.0
fIN = 2.00 Fo-43.0 -48.0
fIN = 0.50 Fo
fIN = 0.50 Fo-0.6 -0.8 -1.0
fIN = 2.00 Fo-11.0 -13.0 -15.0
fIN = 1.00 Fo-2.7 -3.0 -3.3
fIN = 0.25 Fo-0.1 -0.2 -0.3
fIN = 3.00 Fo-30.0 -34.0
MAX296
fIN = 6.00 Fo-74.0 -78.0
Insertion Gain Relative to
DC Gain
fIN = 4.00 Fo-47.0 -51.0
-0.02 -0.1 dB
ppm/°C
FILTER CHARACTERISTICS
MAX291/MAX292/MAX295/MAX296
2
Maxim Integrated
8th-Order, Lowpass,
Switched-Capacitor Filters
ELECTRICAL CHARACTERISTICS (continued)
(V+ = 5V, V- = -5V, filter output measured at OUT pin, 20kΩload resistor to ground at OUT and OP OUT, fCLK = 100kHz
(MAX291/MAX292) or fCLK = 50kHz (MAX295/MAX296), TA= TMIN to TMAX, unless otherwise noted.)
IN = GND
V+ = 5V, V- = -5V, VCLK = 0V to 5V
V- = 0V, GND = V±2
VCLK = 0V or 5V
TA= +25°C, fCLK = 100kHz
fCLK = 100kHz
COSC = 1000pF
CONDITIONS
mA
15 22
4.750 11.000Single Supply
V±2.375 ±5.500
Supply Voltage
Dual Supply
µA0.05Input Bias Current
V±4Output DC Swing
mV±10 ±50Input Offset Voltage
dB0.15 0 -0.15
DC Insertion Gain Error with
Output Offset Removed
mV±150 ±400
V±4Output DC Swing
Output Offset Voltage
1.0Low
V4.0
Clock Input High
(Note 1)
µA±70 ±120
Internal Oscillator
Current Source/Sink
dB-70
Total Harmonic Distortion
plus Noise
mVp-p6Clock Feedthrough
kHz29 35 43
Internal Oscillator
Frequency
UNITSMIN TYP MAXPARAMETER
V+ = 2.375V, V- = -2.375V, VCLK = -2V to 2V 712
Supply Current
CLOCK
UNCOMMITTED OP AMP
POWER REQUIREMENTS
V
V
Typical Operating Characteristics
(V+ = 5V, V- = -5V, TA= +25°C, fCLK = 100kHz (MAX291/MAX292) or fCLK = 50kHz (MAX295/MAX296), unless otherwise noted.)
0
100
50
200
150
300
250
350
450
400
500
0 4682 1012141618
INTERNAL OSCILLATOR PERIOD vs.
CAPACITANCE VALUE
MAX291/2/5/6-01
CAPACITANCE (nF)
OSCILLATOR PERIOD (µs)
0.97
0.94
1.03
1.00
1.06
-60 -20 0 20-40 40 60 80 100 120 140
NORMALIZED INTERNAL OSCILLATOR
FREQUENCY vs. TEMPERATURE
MAX291/2/5/6-03
TEMPERATURE (°C)
NORMALIZED OSCILLATOR FREQUENCY
1nF EXTERNAL
CAPACITOR CLK
Note 1. Guaranteed by design.
MAX291/MAX292/MAX295/MAX296
Maxim Integrated
3
8th-Order, Lowpass,
Switched-Capacitor Filters
-0.6
-0.7
-0.5
-0.2
-0.1
-0.3
-0.4
0
0 200 400 600 800 1k
MAX291/MAX295
FREQUENCY RESPONSE
MAX291/2/5/6-04
INPUT FREQUENCY (Hz)
GAIN (dB)
MAX295
Fo = 1kHz
MAX291
-100
-120
-80
-20
0
-40
-60
20
012345
MAX291/MAX295
FREQUENCY RESPONSE
MAX291/2/5/6-05
INPUT FREQUENCY (Hz)
GAIN (dB)
MAX295
Fo = 1kHz
MAX291
-100
-120
-80
-20
0
-40
-60
20
0246810
MAX292/MAX296
FREQUENCY RESPONSE
MAX291/2/5/6-06
INPUT FREQUENCY (Hz)
GAIN (dB)
MAX296
Fo = 1kHz
MAX292
6
9
8
7
11
10
15
14
13
12
16
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX291/2/5/6-07
SUPPLY VOLTAGE, V+ OR |V-|
SUPPLY CURRENT I+ OR |I-|(mA)
100kHz EXTERNAL CLOCK
10
13
12
11
14
15
16
-60 200-40 -20 40 60 80 100 120 140
SUPPLY CURRENT vs. TEMPERATURE
MAX291/2/5/6-10
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
100kHz EXTERNAL CLOCK
I+ OR | I- |
-60
-70
-50
-20
-10
-30
-40
0
0 400 800 1.2k 1.6k 2k
MAX291/MAX295
FREQUENCY RESPONSE
MAX291/2/5/6-08
INPUT FREQUENCY (Hz)
GAIN (dB)
Fo = 1kHz
MAX291/MAX295
-12
-14
-10
-4
-2
-6
-8
0
0 400 800 1.2k 1.6k 2k
MAX292/MAX296
FREQUENCY RESPONSE
MAX291/2/5/6-09
INPUT FREQUENCY (Hz)
GAIN (dB)
MAX296
Fo = 1kHz
MAX292
-480
-560
-400
-160
-80
-240
-320
0
0 400 800 1.2k 1.6k 2k
MAX291/MAX295
PHASE RESPONSE
MAX291/2/5/6-11
INPUT FREQUENCY (Hz)
PHASE SHIFT (Degrees)
MAX295
Fo = 1kHz
MAX291
0
0 400 1.2k 2k
MAX292/296 PHASE RESPONSE
-300
-350
-100
-150
-50
INPUT FREQUENCY (Hz)
PHASE SHIFT (Degrees)
800 1.6k
-200
-250
fo = 1kHz
MAX291/2/5/6-12
Typical Operating Characteristics (continued)
(V+ = 5V, V- = -5V, TA= +25°C, fCLK = 100kHz (MAX291/MAX292) or fCLK = 50kHz (MAX295/MAX296), unless otherwise noted.)
MAX291/MAX292/MAX295/MAX296
4
Maxim Integrated
8th-Order, Lowpass,
Switched-Capacitor Filters
0
0 0.2 0.4 0.6 1.2 1.4 2.0
MAX296 LOW-VOLTAGE
FREQUENCY RESPONSE
-24
-28
-8
-12
-4
INPUT FREQUENCY (F/FC)
GAIN (dB)
0.8 1.0 1.6 1.8
-16
-20
V+ = +2.5V
V- = -2.5V
FC = 20kHz
FC = 2kHz
MAX291/2/5/6-13
0
1.0 1.1 1.3 1.5
MAX291 LOW-VOLTAGE
FREQUENCY RESPONSE
-24
-28
-8
-12
-4
INPUT FREQUENCY (F/FC)
GAIN (dB)
1.2 1.4
-16
-20
V+ = +2.5V
V- = -2.5V
FC = 20kHz
FC = 1kHz
MAX291/2/5/6-14
-40
12 3 67 10
MAX291 THD + NOISE vs.
INPUT SIGNAL AMPLITUDE
-75
-80
-55
-60
-50
-45
AMPLITUDE (Vp-p)
THD + NOISE (dB)
4589
-65
-70
B
A
A: fCLK = 200kHz Fo = 2kHz
INPUT FREQ. = 200Hz
MEAS. BANDWIDTH = 30kHz
B: fCLK = 1MHz Fo = 1kHz
INPUT FREQ. = 1kHz
MEAS. BANDWIDTH = 80kHz
MAX291/2/5/6-15
0
0 0.2 0.4 0.6 1.2 1.4 2.0
MAX296 LOW-VOLTAGE PHASE RESPONSE
-540
-630
-180
-270
-90
INPUT FREQUENCY (F/FC)
PHASE SHIFT (Degrees)
0.8 1.0 1.6 1.8
-360
-450
V+ = +2.5V
V- = -2.5V
FC = 20kHz
FC = 2kHz
MAX291/2/5/6-16
-40
12 3 67 10
MAX295 THD + NOISE vs.
INPUT SIGNAL AMPLITUDE
-75
-80
-55
-60
-50
-45
AMPLITUDE (Vp-p)
THD + NOISE (dB)
4589
-65
-70
C
D
C: fCLK = 200kHz Fo = 4kHz
INPUT FREQ. = 400Hz
MEAS. BANDWIDTH = 30kHz
D: fCLK = 1MHz Fo = 20kHz
INPUT FREQ. = 2kHz
MEAS. BANDWIDTH = 80kHz
MAX291/2/5/6-19
0
1.0 1.1 1.3 1.5
MAX291 LOW-FREQUENCY
PHASE RESPONSE
-480
-560
-160
-240
-80
INPUT FREQUENCY (F/FC)
PHASE SHIFT (Degrees)
1.2 1.4
-320
-400
V+ = +2.5V
V- = -2.5V
FC = 20kHz
FC = 1kHz
MAX291/2/5/6-17
-40
12 3 67 10
MAX292 THD + NOISE vs.
INPUT SIGNAL AMPLITUDE
-75
-80
-55
-60
-50
-45
AMPLITUDE (Vp-p)
THD + NOISE (dB)
4589
-65
-70
A
B
A: fCLK = 200kHz Fo = 2kHz
INPUT FREQ. = 200Hz
MEAS. BANDWIDTH = 30kHz
B: fCLK = 1MHz Fo = 1kHz
INPUT FREQ. = 1kHz
MEAS. BANDWIDTH = 80kHz
MAX291/2/5/6-18
-40
12 3 67 10
MAX296 THD + NOISE vs.
INPUT SIGNAL AMPLITUDE
-75
-80
-55
-60
-50
-45
AMPLITUDE (Vp-p)
THD + NOISE (dB)
4589
-65
-70
C
D
C: fCLK = 200kHz Fo = 4kHz
INPUT FREQ. = 400Hz
MEAS. BANDWIDTH = 30kHz
D: fCLK = 1MHz Fo = 20kHz
INPUT FREQ. = 2kHz
MEAS. BANDWIDTH = 80kHz
MAX291/2/5/6-20
Typical Operating Characteristics (continued)
(V+ = 5V, V- = -5V, RLOAD = 5kΩ, TA= +25°C, unless otherwise noted.)
MAX291/MAX292/MAX295/MAX296
Maxim Integrated
5
_______________Detailed Description
Lowpass Butterworth filters such as the MAX291/
MAX295 provide maximally flat passband response, making
them ideal for instrumentation applications that require mini-
mum deviation from the DC gain throughout the passband.
Lowpass Bessel filters such as the MAX292/MAX296
delay all frequency components equally, preserving the
shape of step inputs, subject to the attenuation of the high-
er frequencies. They also settle faster than Butterworth fil-
ters. Faster settling can be important in applications that
use a multiplexer (mux) to select one signal to be sent to
an analog-to-digital converter (ADC)—an anti-aliasing filter
placed between the mux and the ADC must settle quickly
after a new channel is selected by the mux.
The difference in the filters’ responses can be observed
when a 3kHz square wave is applied to the filter input
(Figure 1, trace A). With the filter cutoff frequencies set at
10kHz, trace C shows the MAX291/MAX295 Butterworth
filter response and trace B shows the MAX292/MAX296
Bessel filter response. Since the MAX292/MAX296 have a
linear phase response in the passband, all frequency
components are delayed equally, which preserves the
square wave. The filters attenuate higher frequencies of
the input square wave, giving rise to the rounded edges at
the output. The MAX291/MAX295 delay different frequen-
cy components by varying times, causing the overshoot
and ringing shown in trace C.
The MAX291/MAX295 give more attenuation outside the
passband. The phase and frequency response curves in
the
Typical Operating Characteristics
reveal the differences
between the two types of filters.
MAX291/MAX292/MAX295/MAX296 phase shift and gain
do not vary significantly from part to part. Typical phase
shift and gain differences are less than 0.5% at the corner
frequency (FC).
Corner Frequency and Filter Attenuation
The MAX291/MAX292 operate with a 100:1 clock to corner
frequency ratio and a 25kHz maximum corner frequency,
where corner frequency is defined as the point where the
filter output is 3dB below the filter’s DC gain. The
MAX295/MAX296 operate with a 50:1 clock to corner fre-
quency ratio with a 50kHz maximum corner frequency.
The 8 poles provide 48dB of attenuation per octave.
Background Information
Most switched-capacitor filters are designed with biqua-
dratic sections. Each section implements two filtering
poles, and the sections can be cascaded to produce high-
er-order filters. The advantage to this approach is ease of
design. However, this type of design can display poor sen-
sitivity if any section’s Q is high.
An alternative approach is to emulate a passive network
using switched-capacitor integrators with summing and
scaling. The passive network can be synthesized using
CAD programs, or can be found in many filter books.
Figure 2 shows the basic ladder filter structure.
A switched-capacitor filter that emulates a passive ladder
filter retains many of its advantages. The filter’s com-
ponent sensitivity is low when compared to a cascaded
biquad design because each component affects the entire
filter shape, not just one pole pair. That is, a mismatched
component in a biquad design will have a concentrated
8th-Order, Lowpass,
Switched-Capacitor Filters
_____________________Pin Description
Filter Input148
Inverting Input to the uncommit-
ted op amp. The noninverting op
amp is internally tied to ground.
64
Filter Output115
Ground. In single-supply oper-
ation, GND must be biased to
the mid-supply voltage level.
126
Positive Supply pin. Dual sup-
plies: +2.375V to +5.500V. Single
supplies: +4.75V to +11.0V.
137
Uncommitted Op-Amp Output53
Negative Supply pin. Dual
supplies: -2.375V to -5.500V.
Single supplies: V- = 0V.
42
8-PIN
Clock Input. Use internal or
external clock.
31
No Connect
1, 2, 7,
8, 9, 10,
15, 16
FUNCTION16-PIN
IN
OP IN-
OUT
GND
V+
OP OUT
V-
CLK
N.C.
NAME
A
B
AMPLITUDE (5V/div)
C
A: 3kHz INPUT SIGNAL
B: MAX292 BESSEL FILTER RESPONSE WITH Fo = 10kHz
C: MAX291 BUTTERWORTH FILTER RESPONSE WITH Fo = 10kHz
TIME (200µs/div)
Figure 1. Bessel vs. Butterworth Filter Responses
MAX291/MAX292/MAX295/MAX296
6
Maxim Integrated
error on its respective poles, while the same mismatch in a
ladder filter design will spread its error over all poles.
The MAX291/MAX292/MAX295/MAX296 input impedance
is effectively that of a switched-capacitor resistor (see
equation below, and Table 1), and it is inversely proportion-
al to frequency. The input impedance values determined
below represent average input impedance, since the input
current is not continuous. The input current flows in a series
of pulses that charge the input capacitor every time the
appropriate switch is closed. A good rule of thumb is that
the driver’s input source resistance should be less than
10% of the filter’s input impedance. The input impedance
of the filter can be estimated using the following formula:
Z = 1 / (fCLK * C)
where: fCLK = Clock Frequency
The input impedance for various clock frequencies is
given below:
Clock-Signal Requirements
The MAX291/MAX292/MAX295/MAX296 maximum rec-
ommended clock frequency is 2.5MHz, producing a cutoff
frequency of 25kHz for the MAX291/MAX292 and 50kHz
for the MAX295/MAX296. The CLK pin can be driven by
an external clock or by the internal oscillator with an exter-
nal capacitor. For external clock applications, the clock
circuitry has been designed to interface with +5V CMOS
logic. Drive the CLK pin with a CMOS gate powered from
0V and +5V when using either a single +5V supply or dual
+5V supplies. The MAX291/MAX292/MAX295/MAX296
supply current increases slightly (<3%) with increasing
clock frequency over the clock range 100kHz to 1MHz.
Varying the rate of an external clock will dynamically ad-
just the corner frequency of the filter.
Ideally, the MAX291/MAX292/MAX295/MAX296 should
be clocked symmetrically (50% duty cycle). MAX291/
MAX292/MAX295/MAX296 can be operated with clock
asymmetry of up to 60/40% (or 40/60%) if the clock
remains HIGH and LOW for at least 200ns. For example,
if the part has a maximum clock rate of 2.5MHz, then the
clock should be high for at least 200ns, and low for at
least 200ns.
When using the internal oscillator, the capacitance (COSC)
from CLK to ground determines the oscillator frequency:
The stray capacitance at CLK should be minimized be-
cause it will affect the internal oscillator frequency.
___________Application Information
Power Supplies
The MAX291/MAX292/MAX295/MAX296 operate from
either dual or single power supplies. The dual-supply volt-
age range is +2.375V to +5.500V. The ±2.5V dual supply is
equivalent to single-supply operation (Figure 3). Minor per-
formance degradation could occur due to the external
resistor divider network, where the GND pin is biased to
mid-supply.
Input Signal Range
The ideal input signal range is determined by observing at
what voltage level the total harmonic distortion plus noise
(THD + Noise) ratio is maximized for a given corner fre-
quency. The
Typical Operating Characteristics
show the
MAX291/MAX292/MAX295/MAX296 THD + Noise response
as the input signal’s peak-to-peak amplitude is varied.
Uncommitted Op Amp
The uncommitted op amp has its noninverting input tied
to the GND pin, and can be used to build a 1st- or 2nd-
f kHz CpF
OSC OSC
() ()
≈10
3
5
8th-Order, Lowpass,
Switched-Capacitor Filters
C2
R1 L1 L3 L5 L7
VIN
C4 C6 C8 R2
VO
Figure 2. 8th-Order Ladder Filter Network
MAX29_
CLK
1
+1V TO +4V
INPUT SIGNAL
RANGE
5
+5V
OUTPUT
0V
6
3
4
+5V
0V
8
OUT
GND
V-
V+
7
2
OP OUT
OP IN-
IN
0.1µF10k
10k 0.1µF
Figure 3. +5V Single-Supply Operation
Table 1. Input Impedance for Various Clock
Frequencies
1000kHz
(kΩ)
446
305
224
237
100kHz
(MΩ)
4.46
3.05
2.24
2.37
10kHz
(MΩ)
44.6
30.5
22.4
23.7
C (pF)
MAX291 2.24
MAX292 3.28
PART
MAX295 4.47
MAX296 4.22
Pin Configuration is 8-pin DIP.
MAX291/MAX292/MAX295/MAX296
Maxim Integrated
7
8th-Order, Lowpass,
Switched-Capacitor Filters
order continuous lowpass filter. This filter is convenient for
anti-aliasing applications, or for clock noise attenuation at
the switched-capacitor filter’s output. Figure 4 shows a
2nd-order lowpass Butterworth filter built using the
uncommitted op amp with a 10kHz corner frequency.
This filter’s input resistance of 22k satisfies the minimum
load requirements of the switched-capacitor filter.
The uncommitted op amp (with a 2MHz gain bandwidth
product) can alternatively be used at the input of the
switched-capacitor filter to help reduce any possible
clock ripple feedthrough to the output.
DAC Post-Filtering
When using the MAX291/MAX292/MAX295/MAX296 for
DAC post-filtering, synchronize the DAC and the filter
clocks. If clocks are not synchronized, beat frequen-
cies will alias into the desired passband. The DAC’s
clock should be generated by dividing down the
switched-capacitor filter’s clock.
Harmonic Distortion
Harmonic distortion arises from nonlinearities within the
filters. These nonlinearities generate harmonics when a
pure sine wave is applied to the filter input. Table 2 lists
typical harmonic distortion values for the MAX291/
MAX292/MAX295/MAX296 with a 1kHz 5Vp-p sine-wave
input signal, a 1MHz clock frequency, and a 5kΩload.
MAX29_
4
C1
330pF
3
INPUT
C2
1500pF
22k
R1
22k
R2
22k
R3
OUTPUT
OP OUT
OP IN
Figure 4. Uncommitted Op Amp Configured as a 2nd-Order
Butterworth Lowpass Filter (Fo= 10kHz)
Table 2. Typical Harmonic Distortion (dB)
-96
-92
-82
-83
-96
-97
-88
-89
-71
-93
-71
-72
-89
-86
-82
-78
4th 5th2nd 3rd
Filter
Harmonic
MAX296
MAX295
MAX292
MAX291
_Ordering Information (continued)
* Contact factory for dice specifications.
** Contact factory for availability and processing to MIL-STD-883.
Pin Configuration is 8-pin DIP/SO.
8 CERDIP**-55°C to +125°CMAX296MJA
16 Wide SO
8 Plastic DIP
Dice*0°C to +70°C
-40°C to +85°C
-40°C to +85°CMAX296EWE
16 Wide SO0°C to +70°C
MAX296EPA
MAX296C/D
MAX296CWE
8 Plastic DIP
8 CERDIP**
16 Wide SO-40°C to +85°C
-55°C to +125°C
0°C to +70°C
MAX296CPA
MAX295MJA
MAX295EWE
8 Plastic DIP-40°C to +85°CMAX295EPA
Dice*
16 Wide SO0°C to +70°C
0°C to +70°CMAX295C/D
8 Plastic DIP0°C to +70°C
MAX295CWE
MAX295CPA
8 CERDIP**-55°C to +125°CMAX292MJA
16 Wide SO
8 Plastic DIP
Dice*0°C to +70°C
-40°C to +85°C
-40°C to +85°CMAX292EWE
16 Wide SO0°C to +70°C
MAX292EPA
MAX292C/D
MAX292CWE
PIN-PACKAGETEMP. RANGEPART
8 Plastic DIP0°C to +70°C
MAX292CPA
8 SO0°C to +70°CMAX292CSA
8 SO-40°C to +85°CMAX292ESA
8 SO0°C to +70°CMAX295CSA
8 SO-40°C to +85°CMAX295ESA
8 SO0°C to +70°CMAX296CSA
8 SO-40°C to +85°CMAX296ESA
MAX291/MAX292/MAX295/MAX296
8
Maxim Integrated
8th-Order, Lowpass,
Switched-Capacitor Filters
16
15
14
13
12
11
10
9
1
2
3
4
5
6
7
8
N.C.
N.C.
IN
V+
GND
OUT
N.C.
N.C.
N.C.
N.C.
CLK
V-
OP OUT
OP IN-
N.C.
N.C.
TOP VIEW
MAX29_
WIDE SO
____Pin Configurations (continued) Package Information
For the latest package outline information and land patterns, go
to www.maxim-ic.com/packages. Note that a “+”, “#”, or “-” in
the package code indicates RoHS status only. Package draw-
ings may show a different suffix character, but the drawing per-
tains to the package regardless of RoHS status.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
8 CERDIP J8-2 21-0045
8 Plastic DIP P8-2 21-0043
8 SO S8-5 21-0041
16 Wide SO W16-1 21-0042
MAX291/MAX292/MAX295/MAX296
Maxim Integrated
9
8th-Order, Lowpass,
Switched-Capacitor Filters
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
3 12/97 — —
4 4/09 Added MAX292 to Ordering Information table and added new Package
Information section 8
5 5/10 Changed voltage range in Figure 7 7
MAX291/MAX292/MAX295/MAX296
10 Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical
Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
© 2010 Maxim Integrated The Maxim logo and Maxim Integrated are trademarks of Maxim Integrated Products, Inc.
Mouser Electronics
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Maxim Integrated:
MAX291CPA+ MAX291CSA+ MAX291CWE+ MAX291EPA+ MAX291ESA+ MAX292CPA+ MAX292CSA+
MAX292CWE+ MAX295CSA+ MAX295CWE+ MAX296CSA+ MAX296CWE+ MAX291EWE+ MAX292EWE+
MAX295ESA+ MAX295EWE+ MAX296ESA+ MAX296EWE+ MAX291CSA+T MAX291CWE+T MAX291ESA+T
MAX291EWE+T MAX292CSA+T MAX292CWE+T MAX292EPA+ MAX292ESA+ MAX292ESA+T MAX292EWE+T
MAX295CPA+ MAX295CSA+T MAX295CWE+T MAX295EPA+ MAX295ESA+T MAX295EWE+T MAX296CPA+
MAX296CSA+T MAX296CWE+T MAX296EPA+ MAX296ESA+T MAX296EWE+T MAX292EWE/GG8-T