MF4 4th Order Switched Capacitor Butterworth

Lowpass Filter

General Description

The MF4 is a versatile, easy to use, precision 4th order But-

terworth low-pass filter. Switched-capacitor techniques elimi-

nate

external

component

requirements

and

allow

a

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

quency to the low-pass cutoff frequency is internally set to 50

to 1. A Schmitt trigger clock input stage allows two clocking

options, either self-clocking (via an external resistor and ca-

pacitor) for stand-alone applications, or for tighter cutoff fre-

quency control an external TTL or CMOS logic compatible

clock can be applied. The maximally flat passband frequency

response together with a DC gain of 1 V/V allows cascading

MF4 sections together for higher order filtering.

Features

n Low Cost

n Easy to use

n 8-pin mini-DIP or 14-pin wide-body S.O.

n No external components

n 5V to 14V supply voltage

n Cutoff frequency range of 0.1 Hz to 20 kHz

n Cutoff frequency set by external clock

n Separate TTL and CMOS/Schmitt-trigger clock inputs

Connection Diagram

Block Diagram

Dual-In-Line Package

DS005064-2

Order Number MF4CN-50

See NS Package Number N08E

DS005064-1

July 1999

© 1999 National Semiconductor Corporation

DS005064

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