User Guide

PAMS Technical Documentation System Module & UI
NHM-8NX
Issue 1 05/02 ãNokia Corporation Page 37
Figure 12: Headset interface
Analog Audio Accessory Detection
The accessory is detected by the HeadInt signal when the plug is inserted. Normally when
no plug is present, the internal pull-down on the HF pin pulls down the HeadInt signal.
HeadInt comparator value is 1.9V. When the plug is inserted the switch in the connector
is opened and the HeadInt signal is pulled up by the internal pull-up. The 1.9V threshold
level is reached and the comparator output changes to low state causing an interrupt.
Vice versa when the accessory is disconnected the HeadInt switch is closed and the
HeadInt is pulled down.
Table 28: Truth table for HookInt and HeadInt
HeadInt signal is used to detect when the accessory is connected.
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 4-wire fully differential accessories. Detection of the headset
can be split into five main phases:
HookInt HeadInt
Basic Headset, fully differential H H
Button Headset (Switch closed) L H
Button Headset (Switch open) H H
PPH-1 H H
No accessory H L
1k0
Hookint
HeadintHeadint
EAD
MICB2
MIC2P
MIC2N
33N
HFCM
HF
Button
UEM
2.1V
2.7V
33N
1k0
/MBUS
MicGnd
1.8V
0.3V
0.8V
3...25k
Mic_bias
0.8V
Not all components are shown