Features
Cutoff Frequency Selectable in 64 Steps Via Six Bit Control Word
Continuously Tuneable Cutoff Frequency Variable Via External Clock (Crystal, Resonator, or TTL/CMOS Clock)
Cutoff Frequency (fC) Range of 10Hz to 20kHz, 40Hz to 20kHz Via Popular 3.58MHz TV Crystal
Seventh Order Elliptical Ladder Filter with Cosine Prefiltering Stage
Passband Ripple: <0.1dB
Stopband Attenuation: >51dB for f>1.3fC
Uncommitted Input and Output Op Amps for Anti-Aliasing and Smoothing Functions
Steps May Be Custom Programmed from a Set of 2,048 Discrete Points Via Internal ROM
Low Power CMOS Technology
General Description
The S3528B's CMOS design using switched-capacitor techniques allows easy programming of the filter's cutoff frequency (fC) in 64 steps via a six-bit control word. For dynamic control of cutoff frequencies, the S3528B can operate as a peripheral to a microprocessor system which the code for the cutoff frequency being latched in from the data bus. When used with the companion high pass filter, the S3529b, a bandpass or a bandreject filter with a variable center frequency is obtained. For special applications the S3528B's internal ROM can be customized to accommodate a specific set of cutoff frequencies from a choice of 2,048 possibilities.