手机耳机接口插拔识别方案

tches like the FSA8008 resolve this issue by continuously monitoring the mic bias line voltage when a3 pole jack is detected.If a 3 pole plug is ever detected, proprietary circuitry in the FSA8008 close the switch connecting the Mic bias voltage to the 4th pole of the audio jack for a short duration.If the mic line voltage equals ground a 3 pole is still connected, but if the mic line voltage is above 200mV it is a 4 pole headset.The device will recognize this change and output the update on the JPOLE pin to the baseband.The phone will recover from the error, and the microphone will be functional.This solution solves poor user experience by automatically correcting the error and updating the system.

Reduce System Current:

The current system design is not a low power solution; it wastes power in two instances.The current leakages occur with the comparator voltage reference (I2 = 28uA in Figure 1) and when the headset is connected and the microphone is not required (I1 >500uA in Figure 1).Detection switches significantly reduce system current by consolidating the comparator, voltage reference, switch, and logic into one device.In the current solution (Figure 1) the comparator and voltage reference alone represent 48μA (comparator = 20μA + voltage reference =28μA).The total worst case, max current consumption of a detection switch like the FSA8008 is 25uA, saving almost half the current of the comparator and voltage reference alone.Further, the detection switch detects when the audio plug is inserted or removed, when the plug is removed the detection switch automatically enters a low power state of 3μA max.

Understanding the mobile phone’s current operation can further reduce current.For example in MP3 mode the Send/End key can be used for play and pause, but the microphone is not required.In the current solution, the mic line bias is required to identify the Send/End key push.The mic line bias creates leakage current greater than 500uA through RMIC and the microphone.Audio jack detection switches can reduce this current by monitoring for a Send/End key push.Human interfaces like the Send/End key input only require hundreds of milliseconds of accuracy. This allows the detection switch to only need to monitor the Send/End key for a short duration of time.To monitor the Send/End key the internal switch is closed, the mic line bias is measured for a Send/End key push or not.If a key push is detected the Send/End key is debounced and the baseband is notified.If no key push is detected, the internal switch is opened.The duty cycle of this monitor is 90 / 10, saving 90% of the system power over the current solution.

Eliminate Pop-n-Click caused by Microphone Bias

Depending on the design the mic line maybe connected to the 3rd or 4th pole of the audio jack.In either case if the mic bias voltage is present when the audio plug is inserted or removed pop-n-click will be heard, creating a poor user experience.The left and right speakers are connected to the 1st and 2nd poles respectfully and when inserting or removing the plug these poles will scrape past the mic bias voltage causing the pop-n-click.Audio jack detection switches like the FSA8008 have all the components to fully eliminate this issue.The device includes the audio plug insert or removal detection pin (J_DET), the switch to isolate the mic line bias, and the debounce circuitry.When the audio plug is inserted, the J_DET pin detects the connection an