34825 datasheet(21/39 Pages) FREESCALE

21 / 39 page

Analog Integrated Circuit Device Data

Freescale Semiconductor

34825

FUNCTIONAL DEVICE OPERATION

OPERATION AFTER IDENTIFICATION

The operation after the identification is dependent on the

VDDIO voltage. The VDD voltage has to be higher than its

POR threshold for the 34825 to perform the identification

state machine. Once completed, the identification results are

stored in the Status and the ADC Result registers and the

ATTACH bit is set. If the VDDIO is not powered, the interrupt

signal from the INT pin cannot be sent because the INT pin is

normally pulled up to the VDDIO. The host cannot access the

34825 either via the I2C bus. Hence, no communication will

occur between the 34825 and the host IC when the VDDIO is

not powered. The INT signal will send an interrupt signal if the

VDDIO is powered and the ATTACH bit is not masked by the

ATTACH_m bit (refer to Interrupt on page 26 for more

details). If the ATTACH bit is masked while the VDDIO is

powered, the interrupt signal will not be sent but the host IC

can still access the register map via the I2C bus. Once the

host IC accesses the 34825 register map and determines the

accessory type, it can manage the analog switches and other

signals in the 34825 by programming the S/W Control 1 and

S/W Control 2 registers.

The switches are open by default except if the attached

accessory is one of the four test cables listed in Table 21.

More descriptions on the analog switches and the operation

of the 34825 are given in the following sections.

ANALOG SWITCHES

SIGNAL SWITCH ARRAY

The 34825 offers an array of analog switches for signal

switching, as shown in Figure 15. Two pairs of switches (USB

and UART) are for switching the UART and USB signals to

the micro or mini-USB connector. Stereo audio signals can

be switched from the SPK_L and the SPK_R inputs to the DP

and the DM pins that are wired to the USB connector. Both

the SPK_L and the SPK_R inputs are capable of passing

signals of +/-1.5 V, referencing to the GND pin voltage. The

SPK_L and the SPK_R pins are pulled down to ground via a

100 k

Ω resistor respectively, as shown in Figure 15. A

microphone switch connects the MIC pin to the VBUS pin.

All switches are controlled by bits in the S/W Control 1 and

2 registers except when the accessory attached is a test

cable.

SPK_R

SPK_L

MIC

VBUS

RXD

TXD

D+

D-

SW2

SW1

SW3

SW4

SW6

SW7

SW5

OUT

SW8

SW9

SW10

ISET

Gate

Drive

Figure 15. Analog and Digital Switches

POWER MOSFET

The SW8 in Figure 15 is a power MOSFET that controls

the power flow from the VBUS input to the OUT pin. The

power MOSFET serves two purposes. For the Audio

accessory with microphone, the power MOSFET isolates the

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