User Guide

NHM-8NX
System Module & UI PAMS Technical Documentation
Page 38 ãNokia Corporation Issue 1 05/02
1 Micbias is set to high impedance state
2 HeadInt interrupt is detected
3 EAD reading below 0.35V
4 Micbias is set active 2.1V
5 EAD reading 1.0V - 2.2V -> Headset connected
Table 29: Headset identification
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 1.8V 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 treshold level 1.35V. 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 +/- 10mV.
PPH-1 Detection
PPH-1 accessory uses 4-wire fully differential audio connection. The accessory is
detected by the Headint signal when the plug is inserted. PPH-1 has two operating
modes with internal and external microphone. These modes can be separated by reading
the EAD value. Detection of the PPH-1 can be split in four main phases:
1 Micbias is set to high impedance state
2 HeadInt interrupt is detected
3 EAD reading is 2.0V - 2.7V -> PPH-1 connected
Table 30: PPH-1 identification
The PPH-1 has a function of speaker mute. It can be muted by setting micbias in low
Name Function Min Typ Max Uni
t
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
Name Function Min Typ Max Unit Description
Headint Accessory detection 2.2 2.78 2.86 V Accessory connected
Ead / hookint Micbias = High-Z 2.064 2.182 2.302 V PPH-1 External Mic
2.487 2.603 2.720 V PPH-1 Internal Mic
1.840 V PPH-1 Speaker Mute