Audio Input

The MCBTSX1001 board receives audio input from the MIC/IN jack at J1. Configuring JP1 and JP2 in the DIFF position incorporates the low-noise op-amps LNA0 and LNA1 for microphone input. The JK position bypasses these op-amps and JP3 provides a ground to the non-inverted differential input. A 5 VDC microphone bias is provided on pin 3 of the MIC jack when jumper JP6 is installed.

The 2 jumpers at JP13 connect the MIC/IN jack to the low-noise amplifier circuit. Removing these jumpers allows JP13 to be used as a connector for attaching an external analog source to that circuit.

JP5 and JP9 can be used as direct input to the ADC bypassing all op-amp circuitry, if required.

When set to 0, jumper JP11 supplies a 1.2 bandgap buffered voltage reference for the differential amplifier and for the low-noise op-amps LNA0 and LNA1. When set to 1, jumper JP11 supplies a VDD/2 (1.65) buffered voltage reference in both op-amps.