34825 datasheet(24/39 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34825

FUNCTIONAL DEVICE OPERATION

LOGIC CONTROL FEATURES

USB HOST (PC OR HUB)

When the attached accessory is a USB host or hub, the ID

pin is floating. The power MOSFET is turned on to allow the

charger to charge the battery. The ISET outputs default high

impedance to limit the charging current to a lower level. The

host IC can turn on the D+ and D- switches and then pull the

D+ signal to high to start the USB attaching sequence.

USB CHARGER OR DEDICATED CHARGER

When the attached accessory is a USB Charger or a

Dedicated Charger, the 34825 turns on the power MOSFET

to allow the charger to start. The host IC can set the ISET

outputs low impedance to allow a higher charge current.

5-WIRE CARKIT CHARGER (TYPE 1 OR TYPE 2)

A 5-wire carkit charger is a charger specified in the CEA-

936-A USB Carkit Specification. The 5-wire carkit charger

outputs 5V to the VBUS pin, has the D+ and D- pins shorted

internally, and has an ID resistor. The ID resistor has a value

of either 200k

Ω or 440kΩ to distinguish the current capability

of the charger. Refer to the CEA-936-A USB Carkit

Specification for more information.

When the attached accessory is a 5-wire carkit charger,

the 34825 turns on the power MOSFET to allow the Li-ion

battery charging function to start. The host can set the ISET

outputting high impedance or low impedance to choose the

charge current.

RESERVED ACCESSORY

The users can assign the reserved ID resistor values listed

in Table 21 to their user specific accessories. When a user

specific accessory is attached, the identification flow will

identify the ID resistance and as well as the power supply

type in case of a powered accessory. The ADC Result

RID value and the power supply type. The baseband can read

these registers to distinguish the type of the accessory for

further actions.

DETACHING DETECTION

When either the VBUS voltage drops below the VBUS

power detection threshold or the ID resistor is removed, a

detaching detection flow starts. Figure 18 shows the detailed

detection flow. When the DETACH bit is set, the INT outputs

low voltage to inform the host IC. At the end of the detaching

detection flow, the ACTIVE bit is cleared and the 34825

enters the Standby mode. A new identification flow will start

if either the VBUS voltage is above its POR threshold or the

ID resistor is connected.

Figure 18. The Detachment Detection Flow

LOGIC CONTROL FEATURES

RESET

HARDWARE RESET

The 34825 has three sources for hardware resetting the

IC. As the Figure 19 shows, the sources include the Power-

On-Reset caused by the rising VDD, a hardware reset

caused by the VDDIO input and a hardware reset using the

I2C bus lines. The Power-On-Reset is described earlier. The

VBUS

Removed

Clear

VBUS_DET bit

Clear

ATTACH bit

Set

ID_FLOAT bit

ID Float

Yes

Set

DETACH bit

Clear

ACTIVE bit

VBUS=5V

RID

Connected

Yes

34825 Datasheet(PDF) 24 Page - Freescale Semiconductor, Inc

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