Low Noise, 8th Order, Clock Sweepable Cauer Lowpass Filter

The LTC1064-4 is an 8th order, clock sweepable Cauer lowpass switched capacitor filter. An external TTL or CMOS clock programs the value of the filters cutoff frequency. With Pin 10 at V+, the fCLK to fCUTOFF ratio is 50:1; the filter has a Cauer response and with compensation the passband ripple is ±0.1dB. The stopband attenuation is 80dB at 2 × fCUTOFF. Cutoff frequencies up to 100kHz can be achieved. With Pin 10 at V-, the fCLK to f-3dB ratio is 100:1, the filter has a transitional Butterworth-Cauer response with lower noise and lower delay nonlinearity than the Cauer response. The stopband attenuation at 2.5 × f-3dB is 92dB. Cutoff frequencies up to 50kHz can be achieved.

The LTC1064-4 features low noise and low harmonic distortion even when input voltages up to 3VRMS are applied. The LTC1064-4 overall performance competes with equivalent multiple op amp active realizations. The LTC1064-4 is pin compatible with the LTC1064-1, LTC1064-2 and LTC1064-3.

The LTC1064-4 is manufactured using our enhanced LTCMOSTM silicon gate process.

Applications

* Antialiasing Filters

* Telecom Filters

* Sinewave Generators

* 8th Order Filter in a 14-Pin Package

* 80dB or More Stopband Attenuation

at 2 x fCUTOFF

* 50:1 fCLK to fCUTOFF Ratio (Cauer)

* 100:1 fCLK to f-3dB Ratio (Transitional)

* 135µVRMS Total Wideband Noise

* 0.03% THD or Better

* 100kHz Maximum fCUTOFF Frequency

* Operates up to ±8V Power Supplies

* Input Frequency Range up to 50 Times the Filter Cutoff Frequency