19-1821; Rev 0; 11/00
5th-Order, Lowpass,
Switched-Capacitor Filters
General Description
The MAX7418–MAX7425 5th-order, low-pass, switched-
capacitor filters (SCFs) operate from a single +5V
(MAX7418–MAX7421) or +3V (MAX7422–MAX7425)
supply. These devices draw only 3mA of supply current
and allow corner frequencies from 1Hz to 45kHz, mak-
ing them ideal for low-power post-DAC filtering and anti-
aliasing applications. They feature a shutdown mode
that reduces supply current to 0.2µA.
Two clocking options are available: 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 output level.
The MAX7418/MAX7422 deliver 53dB of stopband
rejection and a sharp rolloff with a 1.6 transition ratio.
The MAX7421/MAX7425 achieve a sharper rolloff with a
1.25 transition ratio while still providing 37dB of stop-
band rejection. The MAX7419/MAX7423 Bessel filters
provide low overshoot and fast settling, and the
MAX7420/MAX7424 Butterworth filters provide a maxi-
mally flat passband response. Their fixed response sim-
plifies the design task of selecting a clock frequency.
Features
o
5th-Order, Lowpass Filters
Elliptic Response (MAX7418/MAX7421/
MAX7422/MAX7425)
Bessel Response (MAX7419/MAX7423)
Butterworth Response (MAX7420/MAX7424)
o
Clock-Turnable Corner Frequency (1Hz to 45kHz)
o
Single-Supply Operation
+5V (MAX7418–MAX7421)
+3V (MAX7422–MAX7425)
o
Low Power
3mA (Operating Mode)
0.2µA (Shutdown Mode)
o
Available in 8-Pin µMAX Package
o
Low Output Offset: ±4mV
MAX7418–MAX7425
Ordering Information
PART
MAX7418CUA
MAX7418EUA
MAX7419CUA
MAX7419EUA
MAX7420CUA
MAX7420EUA
MAX7421CUA
MAX7421EUA
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
8 µMAX
8 µMAX
8 µMAX
8 µMAX
8 µMAX
8 µMAX
8 µMAX
8 µMAX
Applications
ADC Anti-Aliasing
DAC Postfiltering
CT2 Base Stations
Speech Processing
Selector Guide
PART
MAX7418
MAX7419
MAX7420
MAX7421
FILTER RESPONSE
r = 1.6
Bessel
Butterworth
r = 1.25
OPERATING
VOLTAGE (V)
+5
+5
+5
+5
Ordering Information continued at end of data sheet.
Typical Operating Circuit
V
SUPPLY
Selector Guide continued at end of data sheet.
Pin Configuration
TOP VIEW
0.1µF
V
DD
INPUT
IN
SHDN
OUT
OUTPUT
COM
1
IN
2
GND
3
8
7
CLK
SHDN
OS
OUT
CLOCK
CLK
MAX7418–
MAX7425
COM
GND
OS
0.1µF
MAX7418–
MAX7425
6
5
V
DD
4
µMAX
________________________________________________________________
Maxim Integrated Products
1
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
5th-Order, Lowpass,
Switched-Capacitor Filters
MAX7418–MAX7425
ABSOLUTE MAXIMUM RATINGS
V
DD
to GND ..............................................................-0.3V to +6V
IN, OUT, COM, OS, CLK,
SHDN
................-0.3V to (V
DD
+ 0.3V)
OUT Short-Circuit Duration.......................................................1s
Continuous Power Dissipation (T
A
= +70°C)
8-Pin µMAX (derate 4.1mW/°C above +70°C) .............330mW
Operating Temperature Ranges
MAX74 _ _C_A ...................................................0°C to +70°C
MAX74 _ _E_A ................................................-40°C to +85°C
Junction Temperature ......................................................+150°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—MAX7418–MAX7421
(V
DD
= +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND,
SHDN
= V
DD
, f
CLK
= 2.2MHz, 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
V
OFFSET
V
IN
= V
COM
= V
DD
/ 2
V
COM
= V
DD
/ 2
(Note 2)
f
IN
= 2KHz,
V
IN
= 4Vp-p,
measurement
bandwidth = 80kHz
OS to OUT
Input, COM externally driven
Output, COM unconnected
Input, OS externally driven
100
10
50
SHDN
= GND, V
COM
= 0 to V
DD
V
OS
= 0 to V
DD
C
OSC
= 1000pF (Note
3)
V
CLK
= 0 or 5V
MAX7418/MAX7421
MAX7419/MAX7420
MAX7418/MAX7421
MAX7419/MAX7420
4.5
0.5
68
86
2.0
2.3
MAX7418/MAX7421
MAX7419/MAX7420
MAX7418
MAX7419
MAX7420
MAX7421
0
-0.2
0.25
±4
0.2
0
-76
-78
-67
-78
1
2.5
2.5
V
COM
±0.1
140
5
R
L
C
L
1
500
±0.1
±0.1
87
110
±40
±50
±10
±10
106
135
±60
±75
3.0
2.7
V/V
V
V
kΩ
mVp-p
kΩ
pF
µA
µA
dB
fc
f
CLK
/ f
C
V
IN
= 4Vp-p (Note 1)
0.001 to 30
100:1
10
V
DD -
0.25
±25
0.4
+0.2
ppm/°C
V
mV
dB
kHz
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Total Harmonic Distortion
plus Noise
Offset Voltage Gain
COM Voltage Range
Input Voltage Range at OS
Input Resistance at COM
Clock Feedthrough
Resistive Output Load Drive
Maximum Capacitive Output
Load Drive
Input Leakage Current at COM
Input Leakage Current at OS
CLOCK
Internal Oscillator Frequency
Clock Output Current
(Internal Oscillator Mode)
Clock Input High
Clock Input Low
THD+N
A
OS
V
COM
V
OS
R
COM
f
OSC
I
CLK
V
IH
V
IL
kHz
µA
V
V
2
_______________________________________________________________________________________
5th-Order, Lowpass,
Switched-Capacitor Filters
ELECTRICAL CHARACTERISTICS—MAX7418–MAX7421 (continued)
(V
DD
= +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND,
SHDN
= V
DD
, f
CLK
= 2.2MHz, 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
±0.2
4.5
0.5
±10
V
V
µA
V
DD
I
DD
I
SHDN
PSRR
Operating mode, no
load
SHDN
= GND
IN = COM (Note 4)
MAX7418/MAX7421
MAX7419/MAX7420
4.5
2.9
3.4
0.2
70
5.5
3.6
4.1
1
V
mA
µA
dB
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX7418–MAX7425
ELECTRICAL CHARACTERISTICS—MAX7422–MAX7425
(V
DD
= +3V, filter output measured at OUT pin, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND,
SHDN
= V
DD
, f
CLK
= 2.2MHz, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
FILTER CHARACTERISTICS
Corner-Frequency Range
Clock-to-Corner Ratio
Clock-to-Corner Tempco
Output Voltage Range
Output Offset Voltage
DC Insertion Gain with Output
Offset Removed
V
OFFSET
V
IN
= V
COM
= V
DD
/ 2
V
COM
= V
DD
/ 2
(Note 2)
f
IN
= 2kHz,
V
IN
= 2.5Vp-p,
measurement
bandwidth = 80kHz
OS to OUT
Input, COM externally driven
Output, COM internally driven
Measured with respect to COM
100
10
50
SHDN
= GND, V
COM
= 0 to V
DD
V
OS
= 0 to V
DD
1.4
1.4
MAX7422/MAX7425
MAX7423/MAX7424
MAX7422
MAX7423
MAX7424
MAX7425
0
-0.2
0.25
±4
0.2
0
-80
-81
-70
-80
1
1.5
1.5
V
COM
±0.1
140
3
R
L
C
L
1
500
±0.1
±0.1
±10
±10
1.6
1.6
V/V
V
V
kΩ
mVp-p
kΩ
pF
µA
µA
dB
f
C
f
CLK
/f
C
V
IN
= 2.5Vp-p
(Note 1)
MAX7422/MAX7425
MAX7423/MAX7424
0.001 to 45
100:1 to 45
100:1
10
V
DD
- 0.25
±25
0.4
+0.2
ppm/°C
V
mV
dB
kHz
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Total Harmonic Distortion plus
Noise
Offset Voltage Gain
COM Voltage Range
Input Voltage Range at OS
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
THD+N
A
OS
V
COM
V
OS
R
COM
_______________________________________________________________________________________
3
5th-Order, Lowpass,
Switched-Capacitor Filters
MAX7418–MAX7425
ELECTRICAL CHARACTERISTICS—MAX7422–MAX7425 (continued)
(V
DD
= +3V, filter output measured at OUT pin, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND,
SHDN
= V
DD
, f
CLK
= 2.2MHz, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
CLOCK
Internal Oscillator Frequency
Clock Output Current (Internal
Oscillator Mode)
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
±0.2
2.5
0.5
±10
V
V
µA
V
DD
I
DD
I
SHDN
PSRR
Operating mode,
no load
SHDN
= GND
Measured at DC
MAX7422/MAX7425
MAX7423/MAX7424
2.7
2.6
3.0
0.2
70
3.6
3.4
3.8
1
V
mA
µA
dB
f
OSC
I
CLK
V
IH
V
IL
C
OSC
= 1000pF
(Note 3)
MAX7422/MAX7425
MAX7423/MAX7424
MAX7422/MAX7425
MAX7423/MAX7424
68
86
68
86
2.5
0.5
87
110
87
110
106
135
106
135
kHz
kHz
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
4
_______________________________________________________________________________________
5th-Order, Lowpass,
Switched-Capacitor Filters
FILTER CHARACTERISTICS
(V
DD
= +5V for MAX7418-MAX7420, V
DD
= +3V for MAX7422-MAX7425 filter output measured at OUT, 10kΩ
||
50pF load to GND at
OUT,
SHDN
= V
DD
, f
CLK
= 2.2MHz, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
ELLIPTIC, R = 1.2—MAX7421/MAX7425
f
IN
= 0.38f
C
f
IN
= 0.68f
C
f
IN
= 0.87f
C
Insertion Gain with DC Gain
Error Removed (Note 4)
f
IN
= 0.97f
C
f
IN
= f
C
f
IN
= 1.25f
C
f
IN
= 1.43f
C
f
IN
= 3.25f
C
BESSEL FILTERS—MAX7419/MAX7423
f
IN
= 0.5f
C
Insertion Gain Relative to
DC Gain
f
IN
= f
C
f
IN
= 4f
C
f
IN
= 7f
C
BESSEL FILTERS—MAX7419/MAX7423
f
IN
= 0.5f
C
Insertion Gain Relative to
DC Gain
f
IN
= 4f
C
f
IN
= 7f
C
-1.0
-3.6
-0.74
-3.0
-41.0
-67
-0.3
-3.6
0
-3.0
-47.5
-70
-2.4
-43
-65
dB
-2.4
-35
-60
dB
-1
-3.6
-0.74
-3.0
-41.0
-67
-2.4
-35
-60
dB
-0.4
-0.4
-0.4
-0.4
-0.7
-0.2
-0.2
-0.2
-0.2
-0.2
-36
-37.2
-37.2
0.4
0.4
0.4
0.4
0.2
-33
-35
-35
dB
CONDITIONS
MIN
TYP
MAX
UNITS
MAX7418–MAX7425
f
IN
= 7f
C
BESSEL FILTERS—MAX7409/MAX7413
BUTTERWORTH FILTERS—MAX7420/MAX7424
f
IN
= 0.5f
C
Insertion Gain Relative to
DC Gain
f
IN
= f
C
f
IN
= 3f
C
f
IN
= 5f
C
Note 1:
The maximum f
C
is defined as the clock frequency f
CLK
= 100 x f
C
at which the peak S / (THD+N) drops to 68dB with a
sinusoidal input at 0.2f
C
. Maximum f
C
increases as V
IN
signal amplitude decreases.
Note 2:
DC insertion gain is defined as
ΔV
OUT
/
ΔV
IN
.
Note 3:
MAX7418/MAX7421/MAX7422/MAX7425: f
OSC
(kHz)
≅
87x10
3
/ C
OSC
(pF).
MAX7419/MAX7420/MAX7423/MAX7424: f
OSC
(kHz)
≅
110x10
3
/ C
OSC
(pF).
Note 4:
PSRR is the change in output voltage from a V
DD
of 4.5V and a V
DD
of 5.5V.
_______________________________________________________________________________________
5
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