LMF120 Datasheet | National Semiconductor

Description The LMF120 is a mask-programmable switched-capacitor filter capable of realizing virtually any filter response up to twelve poles using six independent biquad blocks. It is customized to meet specific application requirements through the use of automated design techniques. Circuit realization occurs during the final metal-mask stage of the manufacturing process. Three sample-and-hold inputs and three buffered outputs allow one, two, or three independent filters on a single chip. Each of the filters may be any type: high-pass, low-pass, allpass, bandpass, or notch. The center or cutoff frequency of each filter is determined by the clock frequency. The clock signal can be supplied by an external source, or it can be generated by the internal oscillator, using an external crystal and two capa Citors. An on-board programmable divider chain can divide the clock input frequency by up to 256 so that each on-chip filter can have a different cutoff/center frequency. Accuracy is enhanced by close matching of the internal ponents: the ratio of the clock frequency to the center/corner frequency is typically accurate to ±0.5%, and is guaranteed to ± 1.5% over the full temperature range. The customization process is initiated by submitting transfer functions, pole and zero locations, or band diagrams to National Semiconductor. A worksheet is included in this datasheet, which can be returned to National Semiconductor for an initial evaluation. Each filter is puter-optimized to best meet the requested specifications, and puter simulations are produced for approval before prototyping begins. Features - Mask-programmable for virtually any filter response - All filter types (low-pass, high-pass, bandpass, notch, all-pass) - All filter approximations (Butterworth, Chebyshev, Ellip- tic, Bessel, etc.) - Up to 12 poles and right-half-plane zeros in one 16-pin package - One, two, or three filters per package - Wide Q range: up to 100 per biquad - Choice of internal or...