Patent ID: 9479882
Filing Date: 2016-10-25
CPC Classification: H04R

Claim Text:
1. An audio accessory key detection system comprising: (a) a host circuit including a host controller, and a bias circuit coupled by a first resistor to a microphone out line; (b) a host transceiver in the host circuit coupled to the microphone out line and the host controller; (c) an analog to digital converter in the host circuit for digitizing an analog signal level on the microphone out line and conveying a digital representation of the analog signal level to the host controller during an analog mode of operation; and (d) an accessory circuit including: (i) a microphone in line coupled to the microphone out line; (ii) a microphone and bias circuit coupled to the microphone in line; (iii) an energy storage circuit coupled between the microphone in line and ground and having a supply voltage conductor; (iv) an accessory transceiver having a line coupled with the microphone in line, a data in line, and a data out line; (v) a key detector and controller circuit having a data input coupled to the data in line, a data output coupled to the data out line, a power input coupled to the supply voltage conductor, an enable output, a first key conductor input, and a second key conductor input; (vi) a first key connected between the first key conductor input and ground; (vii) a second key connected between the second key conductor and ground through a first resistor; (viii) a first switch transistor coupled from the microphone in line to between the first key conductor input and the first key and having a control input; (ix) a second switch transistor coupled from the microphone in line to between the second key conductor input and the second key and having a control input; and (x) a charge pump having an enable input coupled to the enable output, a supply voltage input coupled to the supply voltage conductor, and an output coupled to the control inputs of the switch transistors.