MC34708 datasheet(98/159 Pages) FREESCALE

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Analog Integrated Circuit Device Data



Freescale Semiconductor

MC34708

Functional Block Description

Raw Data (Raw Data Bit)

The RAW DATA bit functions only when the accessory is Audio Type 1, which supports the remote control key. The RAW DATA

bit determines whether to report the ID pin resistance change to the baseband when any key is pressed. When RAW DATA = 1,

the ADC is enabled only when an ID line event is detected, such as when a key is pressed. In this case, the interrupt bits KP,

LKP, or LKR, and the corresponding button bits in Button 1 and Button 2 registers, will be set accordingly. Detailed behavior

information when RAW DATA = 1 can be found in Audio Type 1 Operation Mode.

Audio Device Type 1 - Audio with or without the Remote Control. When RAW DATA = 0, the ADC is enabled periodically to

calculate the ID line resistance. Any change of ADC Result will set the ADC_Change interrupt bit to inform the baseband. The

baseband can read the ADC result via the SPI. The KP, LKP, or LKR, and the button bits, will not set when RAW DATA = 0. The

period of ADC conversion is determined by the Device Wake-up bits in the USB Timing register. All other behaviors of Audio

Type 1 and other accessories will not be affected by the RAW DATA bit. LKR and the button bits will not set when RAW DATA = 0.

The period of ADC conversion is determined by the Device Wake-up bits in the Timing Set 1 register. All other behaviors of Audio

Type 1 and other accessories will not be affected by the RAW DATA bit.

7.8.4.7

Analog and Digital Switches

The signal switches in the MC34708 are shown in Figure 26. These switches are controlled by the identification result when the

Manual S/W = 1, and by the Manual SW/Result register, when the Manual S/W = 0 is in Active mode. The Switch_Open bit

overrides the switch configuration. When the Switch_Open bit is 0, all switches are turned off. The switches for the SPK_L and

SPK_R are capable of passing signals of

1.5 V, referencing to the GND pin voltage. The SPK_L and SPK_R pins are pulled

down to GND via a 100 k

 resistor respectively, as shown in Figure 26. When the switches are configured automatically by the

identification result, the configuration of the switches vs. the device type is shown in Table 93.

When detachment of an accessory is detected, the MC34708 will return to Standby mode. In Standby mode, regardless of the

Manual S/W = 1 or Manual S/W = 0 state, all signal switches and are off in the Standby mode. The OUT-to-ground FET is turned

on whenever the FET_ON bit is '0'.

Figure 26. Analog and Digital Switches

SPK_R

SPK_L

MIC

VBUS

RxD

TxD

D+

D-

SW2

SW1

SW3

SW4

SW6

SW7

SW5

VUSB

LDO

VINUSB

MOTG

MC34708 数据表(PDF) 98 Page - Freescale Semiconductor, Inc

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