LF43881

` 25 MHz Maximum Sampling Rate
` 320 MHz Multiply-Accumulate Rate
` 8 Filter Cells
` 8-bit Unsigned or Two's Complement Data
` 8-bit Unsigned or Two's Complement Coefficients
`26-bit Data Outputs
` Shift-and-Add Output Stage for Combining Filter Outputs
` Expandable Data Size, Coefficient Size, and Filter Length
` User-Selectable 2:1, 3:1, or 4:1 Decimation
` Replaces Harris HSP43881
` 84-pin PLCC, J-Lead

The LF43881 is a video-speed digital filter that contains eight filter cells (taps) cascaded internally and a shiftand-
add output stage. An 8 x 8 multiplier, three decimation registers, and a 26-bit accumulator are contained in each filter cell. The output stage of the LF43881 contains a 26-bit accumulator which can add the contents of any filter stage to the output stage accumulator shifted right by 8 bits. 8-bit unsigned or two's complement format for data and coefficients can be independently selected.

Expanded coefficients and word sizes can be processed by cascading multiple LF43881s to implement larger filter lengths without affecting the sample rate. By reducing the samplerate, a single LF43881 can process larger filter lengths by using multiple passes. The sampling rate can range from 0 to 40 MHz. Over 1000 taps may be processed without overflows due to the architecture of the device.

The output sample rate can be reduced to one-half, one-third, or onefourth the input sample rate by using the three decimation registers contained in every filter cell. Matrix multiplication, N x N spatial correlations/ convolutions, and other 2-D operations for image processing can also be achieved using these registers.