34825 datasheet(17/39 Pages) FREESCALE

17 / 39 page

Analog Integrated Circuit Device Data

Freescale Semiconductor

34825

FUNCTIONAL DEVICE OPERATION

POWER-UP

detecting audio signal activities or an accessory detachment.

If the transition is caused by an accessory detachment, the

34825 moves from the Power Save mode to the Standby

mode directly. Otherwise, it moves to the Active mode, and

the configuration of the IC resumes to the same configuration

before entering the Power Save mode.

DEVICE MODE REGISTER

The PSAVE bit, ACTIVE bit and RST bit in the Device

Mode register (refer to Table 9) hold the information of the

device operational mode. The RST bit, which is of R/C (read

and clear) type, indicates whether a reset has occurred. The

RST bit is set when a reset occurs (refer to Reset for more

information). The RST bit is cleared when read by an I2C

access. The ACTIVE bit and the PSAVE bit together indicate

the device mode by the relationship shown in Table 5. When

the device is in the VBUS Power mode, the registers are not

powered up.

The ACTIVE bit is a R/W (read and write) bit, it can be

written by an I2C operation. When the host IC writes ‘0’ to the

ACTIVE bit, the device will be forced to the Standby mode. If

an accessory is attached when the ACITVE is set to 0, the

accessory identification flow shown in Figure 14 will be re-

started.

The PSAVE bit is also a R/W bit. When the 34825 is

configured to the Auto Power-save mode (AutoPSAVE bit is

set to 1), the PSAVE bit indicates whether the 34825 is in the

Power Save mode or not. When the 34825 is configured to

the Manual Power-save mode (AutoPSAVE bit set to 0), the

host IC can writes ‘1’ to the PSAVE bit to force the 34825 into

the Power Save mode when an Audio R/C accessory is

attached. For all other accessories attachment, the 34825

does not enter the Power Save mode even the PSAVE bit is

set to 1.

Table 5. The Device Modes vs. the Register Bits

PSAVE

ACTIVE

MODE

Standby

Active

Power Save

Undefined

POWER-UP

The 34825 has four possible power-up scenarios

depending on which of the VDD pin and the VBUS pin is

powered up first. The four scenarios correspond to the

following four mode transitions.

1. From Power Down to VBUS Power: the VBUS pin is

powered up when VDD < VVDDPOR (VDD POR

threshold)

2. From VBUS Power to Standby: VBUS is already

powered when the VDD voltage rises above its POR

threshold

3. From Power Down to Standby: the VDD pin is

powered up when VBUS < VVBUSPOR (VBUS POR

threshold)

4. From Standby to Active: the VDD pin is already

powered when the VBUS voltage rises above its POR

threshold

SCENARIO 1: VDD = 0 V AND VBUS IS POWERED

UP (POWER DOWN MODE TO VBUS POWER

MODE TRANSITION)

If the VDD pin is not powered but the VBUS is powered up

within a voltage range between the POR threshold and the

OVP (over-voltage protection) threshold, the internal power

MOSFET is softly turned on. The IC is in the VBUS Power

mode.

In this VBUS Power mode, the ISET outputs high-

impedance and all registers are in the reset state. The power

MOSFET remains on unless it is disabled by the over-voltage

protection or the over-temperature protection block.

SCENARIO 2: VBUS = HIGH AND VDD IS

POWERED UP (VBUS POWER MODE TO STANDBY

MODE TRANSITION)

If the VBUS pin is already powered when the VDD pin is

powered up, the device moves from the VBUS Power mode

to the Standby mode and then quickly moves to the

identification flow of the Active mode to identify the

accessory, as shown in Figure 14.

After the VDD pin is powered up, the 34825 starts up the

internal supplies. The POR resets all register bits. The power

MOSFET remains on during the reset process.

SCENARIO 3: VBUS = 0 V AND VDD IS POWERED

UP (POWER DOWN MODE TO STANDBY MODE

TRANSITION)

If no accessory is plugged into the micro or mini-USB

connector when VDD is powered up, the 34825 moves from

the Power Down mode to the Standby mode. The internal

supplies are started up first, and then the whole chip is reset

and is ready to accept accessories. Then when an accessory

is attached, the 34825 enters the Active mode. The power

MOSFET is off in this case since VBUS = 0 V.

SCENARIO 4: VDD = HIGH AND VBUS IS

POWERED UP (STANDBY TO ACTIVE MODE

TRANSITION)

This is a normal VBUS detection case as shown in

Figure 14. More description can be found in Power Supply

Type Identification.

34825 Datasheet(PDF) 17 Page - Freescale Semiconductor, Inc

34825 Datasheet(HTML) 17 Page - Freescale Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

Datasheet Download

Link URL