Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsLinear ICsMAX7401CSA+

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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.

Applications

ADC Anti-Aliasing CT2 Base Stations

Post-DAC Filtering Speech Processing

Air-Bag Electronics

Features

♦ 8th-Order, Lowpass Bessel Filters

♦ Low Noise and Distortion: -82dB THD + Noise

♦ Clock-Tunable Corner Frequency (1Hz to 5kHz)

♦ 100:1 Clock-to-Corner Ratio

♦ Single-Supply Operation

+5V (MAX7401)

+3V (MAX7405)

♦ Low Power

2mA (Operating Mode)

0.2µA (Shutdown Mode)

♦ Available in 8-Pin SO/DIP Packages

♦ Low Output Offset: ±5mV

MAX7401/MAX7405

8th-Order, Lowpass, Bessel,

Switched-Capacitor Filters

________________________________________________________________

Maxim Integrated Products

OUTV

CLK

SHDNIN

GND

COM

SO/DIP

TOP VIEW

MAX7401

MAX7405

CLK

OUT

GND

INPUT

0.1µF

CLOCK

SHDN

OUTPUT

SUPPLY

COM

MAX7401

MAX7405

Typical Operating Circuit

19-4788; Rev 1; 6/99

Pin Configuration

Ordering Information

PART

MAX7401CPA

MAX7401ESA

MAX7401EPA -40°C to +85°C

-40°C to +85°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

8 Plastic DIP

8 SO

8 Plastic DIP

MAX7405CSA

MAX7405CPA

MAX7405ESA

MAX7405EPA -40°C to +85°C

-40°C to +85°C

0°C to +70°C

0°C to +70°C 8 SO

8 Plastic DIP

8 SO

8 Plastic DIP

MAX7401CSA

0°C to +70°C 8 SO

Summary of content (12 pages)

PAGE 1
9-4788; Rev 1; 6/99 8th-Order, Lowpass, Bessel, Switched-Capacitor Filters Features ♦ 8th-Order, Lowpass Bessel Filters ♦ Low Noise and Distortion: -82dB THD + Noise ♦ Clock-Tunable Corner Frequency (1Hz to 5kHz) ♦ 100:1 Clock-to-Corner Ratio ♦ Single-Supply Operation +5V (MAX7401) +3V (MAX7405) ♦ Low Power 2mA (Operating Mode) 0.
PAGE 2
MAX7401/MAX7405 8th-Order, Lowpass, Bessel, Switched-Capacitor Filters ABSOLUTE MAXIMUM RATINGS VDD to GND MAX7401 ..............................................................-0.3V to +6V MAX7405 ..............................................................-0.3V to +4V IN, OUT, COM, OS, CLK ...........................-0.3V to (VDD + 0.3V) SHDN........................................................................-0.3V to +6V OUT Short-Circuit Duration...................................................
PAGE 3
8th-Order, Lowpass, Bessel, Switched-Capacitor Filters (V DD = +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF from COM to GND, SHDN = VDD, fCLK = 100kHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS SYMBOL MIN UNITS TYP MAX 5.5 V 2 3.5 mA 1 µA POWER REQUIREMENTS Supply Voltage VDD Supply Current IDD 4.
PAGE 4
MAX7401/MAX7405 8th-Order, Lowpass, Bessel, Switched-Capacitor Filters 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 = VDD, fCLK = 100kHz, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.
PAGE 5
8th-Order, Lowpass, Bessel, Switched-Capacitor Filters PASSBAND FREQUENCY RESPONSE -1.0 -30 -2.0 -50 -2.5 -60 -3.0 -70 1 2 3 4 202 606 808 MAX7409 toc02 1010 0 1200 1600 NO LOAD 20 VIN = VCOM = VDD / 2 15 OFFSET VOLTAGE (mV) SUPPLY CURRENT (mA) 2.02 2.01 MAX7401 2.00 1.99 1.5 4.0 4.5 5.0 -40 -20 0 SUPPLY VOLTAGE (V) 0.5 0 -0.5 -1.0 20 40 60 80 0 20 40 60 TEMPERATURE (°C) 80 100 2.5 3.0 3.5 4.0 4.5 5.0 5.
PAGE 6
Typical Operating Characteristics (continued) (VDD = +5V for MAX7401, VDD = +3V for MAX7405; fCLK = 100kHz; SHDN = VDD; VCOM = VOS = VDD / 2; TA = +25°C; unless otherwise noted.) THD + NOISE (dB) 1.01 MAX7405 0.99 0.98 -40 -50 -60 A -70 0.
PAGE 7
8th-Order, Lowpass, Bessel, Switched-Capacitor Filters PIN NAME FUNCTION 1 COM Common Input. Biased internally at mid-supply. Bypass externally to GND with a 0.1µF capacitor. To override internal biasing, drive with an external supply. 2 IN 3 GND Ground 4 VDD Positive Supply Input: +5V for MAX7401, +3V for MAX7405 5 OUT Filter Output 6 OS 7 SHDN 8 CLK Filter Input Offset Adjust Input. To adjust output offset, bias OS externally. Connect OS to COM if no offset adjustment is needed.
PAGE 8
MAX7401/MAX7405 8th-Order, Lowpass, Bessel, Switched-Capacitor Filters A switched-capacitor filter such as the MAX7401/ MAX7405 emulates a passive ladder filter. The filter’s component sensitivity is low when compared to a cascaded biquad design because each component affects the entire filter shape, not just one pole-zero pair.
PAGE 9
8th-Order, Lowpass, Bessel, Switched-Capacitor Filters FILTER fCLK (kHz) fC (kHz) fIN (Hz) 100 1 200 VIN (Vp-p) MAX7401 TYPICAL HARMONIC DISTORTION (dB) 2nd 3rd 4th 5th -91 -83 -90 -93 -89 -79 -92 -92 -87 -83 -87 -88 -83 -82 -88 -88 4 500 5 1000 100 1 200 MAX7405 2 500 5 1000 Anti-Aliasing and Post-DAC Filtering When using the MAX7401/MAX7405 for anti-aliasing or post-DAC filtering, synchronize the DAC and the filter clocks.
PAGE 10
________________________________________________________Package Information SOICN.
PAGE 11
8th-Order, Lowpass, Bessel, Switched-Capacitor Filters PDIPN.
PAGE 12
MAX7401/MAX7405 8th-Order, Lowpass, Bessel, Switched-Capacitor Filters NOTES 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.