Functional Description; Audio External; Headset Detection; Fig 4 External Audio Interface - Nokia RH-53 Manual

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Functional Description

Audio External

RH-53/54 is designed to support fully differential external audio accessory connection. A head-
set and PnPHF can be directly connected to system connector. Detection of the different ac-
cessories is made in analog way by reading the DC voltage value of EAD converter.
2.7V
Hookint
/MBUS
EAD
Headint Headint
Mic_bias
MICB2
MIC2P
MIC2N
HF
3...25k
HFCM
UEM

Headset Detection

Supported headsets are 4-wire fully differential accessories. The hardware used to detect ac-
cessories is contained in the UEM and BB area. For interrupt purposes the UEM inputs
HOOKINT and HEADINT are used. The bottom connector contains a switch, which opens
when an accessory is connected. The switch is routed to the UEM HEADINT input.
The current generators on the HOOKINT and HEADINT pins acts as internally pull-up resistors
with values equivalent to 675 k - 2.86 M, tolerances of the current source and VFLASH1 con-
sidered. The HOOKINT input comparator threshold level can be set to two different values.
Levels can be found in the table.
Table 13: Comparator threshold levels and pull-up current source strength (hysteresis included)
Parameter
HOOKINT comparator thresh-
old
22
Figure 4:External audio interface
Not all components are shown
1k0
2.1V
33N
33N
0.8V
0.8V
1k0
Variable
Vhook1
COMPANY CONFIDENTIAL
Copyright © 2004 Nokia. All Rights Reserved.
1.8V
0.3V
Min Typ
1.21 V 1.35 V
RH-53/54
8-System Module
Bottom
Connector
MicGnd
Max
1.49 V
ISSUE 1 09/2004