Document
19-1821; Rev 0; 11/00
MAX7418–MAX7425
5th-Order, Lowpass, Switched-Capacitor Filters
General Description
The MAX7418–MAX7425 5th-order, low-pass, switchedcapacitor 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, making them ideal for low-power post-DAC filtering and antialiasing 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 stopband rejection. The MAX7419/MAX7423 Bessel filters provide low overshoot and fast settling, and the MAX7420/MAX7424 Butterworth filters provide a maximally flat passband response. Their fixed response simplifies the design task of selecting a clock frequency.
Applications
ADC Anti-Aliasing DAC Postfiltering
CT2 Base Stations Speech Processing
Selector Guide
PART
FILTER RESPONSE
OPERATING VOLTAGE (V)
MAX7418
r = 1.6
+5
MAX7419
Bessel
+5
MAX7420
Butterworth
+5
MAX7421
r = 1.25
+5
Selector Guide continued at end of data sheet.
Pin Configuration
TOP VIEW
COM 1 IN 2
GND 3 VDD 4
MAX7418– MAX7425
8 CLK 7 SHDN 6 OS 5 OUT
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
Ordering Information
PART
TEMP. RANGE PIN-PACKAGE
MAX7418CUA
0°C to +70°C
8 µMAX
MAX7418EUA
-40°C to +85°C 8 µMAX
MAX7419CUA
0°C to +70°C
8 µMAX
MAX7419EUA
-40°C to +85°C 8 µMAX
MAX7420CUA
0°C to +70°C
8 µMAX
MAX7420EUA
-40°C to +85°C 8 µMAX
MAX7421CUA
0°C to +70°C
8 µMAX
MAX7421EUA
-40°C to +85°C 8 µMAX
Ordering Information continued at end of data sheet.
Typical Operating Circuit
VSUPPLY
0.1µF INPUT CLOCK
VDD SHDN
IN OUT
MAX7418– MAX7425
CLK COM OS
GND
OUTPUT 0.1µF
µMAX
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5th-Order, Lowpass, Switched-Capacitor Filters
MAX7418–MAX7425
ABSOLUTE MAXIMUM RATINGS
VDD to GND ..............................................................-0.3V to +6V IN, OUT, COM, OS, CLK, SHDN ................-0.3V to (VDD + 0.3V) OUT Short-Circuit Duration.......................................................1s
Continuous Power Dissipation (TA = +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
(VDD = +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF capacitor from COM to GND, SHDN = VDD, fCLK = 2.2MHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
FILTER CHARACTERISTICS
Corner Frequency Clock-to-Corner Ratio Clock-to-Corner Tempco
fc VIN = 4Vp-p (Note 1) fCLK / fC
0.001 to 30 100:1 10
kHz ppm/°C
Output Voltage Range Output Offset Voltage
DC Insertion Gain with Output Offset Removed
VOFFSET
VIN = VCOM = VDD / 2
VCOM = VDD / 2 (Note 2)
MAX7418/MAX7421 MAX7419/MAX7420
0.25
0 -0.2
VDD - 0.25 ±4 ±25 0.2 0.4 0 +0.2
V mV
dB
Total Harmonic Distortion plus Noise
THD+N
fIN = 2KHz, VIN = 4Vp-p, measurement
bandwidth = 80kHz
MAX7418 MAX7419 MAX7420 MAX7421
-76 -78
dB -67 -78
Offset Voltage Gain COM Voltage Range
AOS VCOM
OS to OUT Input, COM externally driven Output, COM unconnected
1 2.0 2.5 3.0 2.3 2.5 2.7
V/V V
Input Voltage Range at OS Input Resistance.