External Audio Interface Electrical Interface

The external audio connections are presented in the following two diagrams. A headset or a handsfree can be connected directly to the system connector. The headset microphone bias is supplied from COBBA AUXOUT output and fed to the microphone through XMICP line.

R1Ü4 1k i pin7_XMICP

L400

EEPROMSelX MAD

1SS355 V103

C401_1

C401_2 27p

C406 1 n

R103_1

i VARISTOR I R420

R105_1

22k C100_1

100n cm

R103_2 100k pin5_XMICN

VARISTOR R421

R106_2 1k

C102_1 10n

C102_2 10n

R105_2 2.2k

AUXOUT COBB/

EAD CCOHT

MIC1P COBBA

MIC1N COBBA

MIC3P COBBA

MIC3N COBBA

R100_2 47k

HOOKDET MAD

R101 330k

BC848W/PLP

Figure 28: External Audio Interface - Microphone

Figure 28: External Audio Interface - Microphone

Figure 29: External Audio Interface - Speaker

HEADDET and HOOKDET are both the same type of'interrupts input' in MAD.

The characteristicfor these interrupts isshown in Triggering levels/Forbidden Operating Range-HEADDETand HOOKDET.

Figure 30: Triggering levels/Forbidden Operating Range-HEADDET and HOOKDET

If operating outside the ranges 0-0.8 Vdc or 1.8-2.8Vdc the interrupt inputs will start pulling current.

EAD is an analogue input on CCONT used to measure the DC-voltage on MIC1P line. This voltage value is used to identify the accessories and to control their function.

HF and HFCM are two audiooutputs through which audio can be routed to either HS-earpiece or PPH-1 speaker. HF and HFCM are externally wired as fully- differential outputs, however it is only HF which in reality performs the audio-amplification.

MIC1P, MIC1N, MIC3P and MIC3N are all inputs to the microphone amplifier in COBBA. In short form the main difference for the listed inputs are :

MIC1P, MIC1N : Rated to audiosignals up to 2 Vpp. Used for PPH-1 microphone.

MIC3P, MIC3N : Rated to audiosignals up to 200 mVpp. Used for HS microphone.

Both types of inputs can be wired and used to either fully differentiel or singled-ended operation, however the fully differential configuration is chosen for the Janette interface.

MIC1 and MIC3 must be isolated from each other DC-wise !

AUXOUT is an output having two functions in the Janette Accessory interface: Biasing purposes for the HeadSet-microphone

Controlling purposes for the PPH-1. AUXOUT can be set to the following states by the MCU-SW :

High Impedance (Z)

2.1 Vdc

1.5 Vdc

Low Impedance (0 Vdc)

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