TH7301

The TH7301 incorporates two matching 4th-order Butterworth filters with voltage gain control to perform low-pass filtering on quadrature demodulated signals. The cutoff frequency and inband gain are programmable via a standard 3-wire interface. The cutoff frequency can be set between 0.8 MHz and 22.4 MHz and the inband voltage gain can be set between -3 dB and 20 dB. The cutoff frequency value is determined via a 10-bit control word, with smaller step sizes in the lower portion of the cutoff frequency range. The TH7301 contains an on-chip oscillator to adjust the cutoff frequency. Maintaining amplifiers configure the Butterworth filter as the phase shift component of the oscillator. The frequency of oscillation tracks the filter cutoff frequency. The cutoff frequency of the filter can be accurately set according to the resolution of the IC by measuring the frequency of oscillation.