MF6

6th Order Switched Capacitor Butterworth Lowpass

Filter

General Description

The MF6 is a versatile easy to use, precision 6th order But-

terworth lowpass active filter. Switched capacitor techniques

eliminate external component requirements and allow a

clock tunable cutoff frequency. The ratio of the clock fre-

quency to the lowpass cutoff frequency is internally set to 50

to 1 (MF6-50) or 100 to 1 (MF6-100). A Schmitt trigger clock

input stage allows two clocking options, either self-clocking

(via an external resistor and capacitor) for stand-alone appli-

cations, or an external TTL or CMOS logic compatible clock

can be used for tighter cutoff frequency control. The maxi-

mally flat passband frequency response together with a DC

gain of 1 V/V allows cascading MF6 sections for higher order

filtering. In addition to the filter, two independent CMOS op

amps are included on the die and are useful for any general

signal conditioning applications.

Features

n No external components

n Cutoff frequency range of 0.1 Hz to 20 kHz

n Two uncommitted op amps available

n 5V to 14V total supply voltage

n Cutoff frequency set by external or internal clock

Block and Connection Diagrams

All Packages

DS005065-2

Top View

Order Number MF6CWM-50

or MF6CWM-100

See NS Package Number M14B

DS005065-1

June 1999

© 1999 National Semiconductor Corporation

DS005065

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