User Guide

NPM-10 (3595)

System Module CC Technical Documentation

The HeadInt signal is used to detect when the accessory is connected. The HookInt signal

is used to detect when the button of the headset is pressed.

Note: Charging must be disabled during identification of PPH-1.

Headset Detection

Supported headsets are four-wire fully differential accessories. Detection of the headset

can be split into five main phases:

1. Micbias is set to high impedance state

2. HeadInt interrupt is detected

3. EAD reading below 0.35 V

4. Micbias is set active 2.1 V

5. EAD reading 1.0 V - 2.2 V -> Headset connected

The hook signal is generated by creating a short circuit between the headset microphone

signals. When no accessory is present, the HookInt signal is pulled up by the UEM. When

the accessory is inserted and the microphone path is biased, the HookInt signal decreases

to 1.8 V due to the microphone bias current flowing through the upper bias resistor net-

work. When the button is pressed, the microphone signals are connected together and

the HookInt will fall below trigger threshold level (1.35 V). This change in DC level will

cause the HookInt comparator output to change state.

HeadInt comparator reference level is 1.90 V, +/- 0.15 V. HookInt comparator reference

is selected by SW. Used trigger level is 1.35 V, +/- 10 mV.

PPH-1 H H

No accessory H L

Table 26: Headset Identification

Name Function Min Type Max Unit Description

Headint Accessory detection 2.2 2.78 2.86 V Accessory connected

Ead / hookint Micbias=High-Z 0.35 V Headset

Micbias active 2.1V 1.009 1.07 1.163 V Headset button closed

1.596 1.85 2.140 V Headset button open

Table 25: Truth Table for HookInt and HeadInt (Continued)

Accessory HookInt HeadInt