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Maxim > Design Support > Technical Documents > Application Notes > Filter Circuits (Analog) > APP 23

Keywords: analog filter, microprocessor supervisor, uP supervisor, reset circuit, power fail comparator

APPLICATION NOTE 23

µP-Supervisor Chip Controls Programmable Filter

Jul 09, 1998

Abstract: An application showing how the use of a microprocessor supervisor can be used to program a dual

section filter. Using the time delay from the reset circuit and strapping it to the power-fail comparator with a

delay circuit, the filter can easily be programmed to provide the correct cutoff frequencies during power up

using this reset circuit.

require a different f

C

for each section. In such cases, a microprocessor is the obvious tool for sequentially

programming the two filter sections, but lacking a µP, you can do the job without the circuit of Figure 1.

Figure 1. A µP-supervisory chip (IC1) directs the sequential loading of f

C

data into the dual, programmable

lowpass filter IC2. The circuit reloads this f

IC