34825 datasheet(22/39 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

34825

FUNCTIONAL DEVICE OPERATION

OPERATION AFTER IDENTIFICATION

VBUS pin from both the input decoupling capacitor and the

input quiescent current of the charger IC connected to the

OUT pin, so that the microphone signal can be connected to

the VBUS pin without any interference from the OUT pin. The

power MOSFET is also used as the input Over-voltage

Protection (OVP) or Over-current Protection (OCP) switch for

other components in the cell phone, such as the charger IC,

to allow a low voltage rated charger IC to be used for cost

reduction.

The power MOSFET is guaranteed to be turned on in

VBUS power mode even when the VDD voltage is below

VVDDPOR threshold, to ensure that the cell phone battery can

be charged when the battery is fully discharged.

PROTECTION

OVER-VOLTAGE PROTECTION (OVP)

The VBUS line is capable of withstanding a 28 V voltage.

The 34825 protects the cell phone by turning off the internal

power MOSFET when the VBUS voltage is higher than the

OVP threshold. In this case, the 34825 turns off the power

MOSFET within 1.0

μs after the input voltage exceeds the

OVP threshold, and the OVP_EN bit in the Interrupt register

is set to interrupt the host IC. When the OVP event is cleared,

the OVP_OTP_DIS bit in the Interrupt register is set to inform

the host IC.

OVER-CURRENT PROTECTION (OCP) AND OVER-

TEMPERATURE PROTECTION (OTP)

If the current flowing through the power MOSFET exceeds

the specified OCP limit, the 34825 will operate in CC

(Constant Current) mode, regulating the output current at the

OCP limit. If the OCP condition persists, the IC temperature

will rise, eventually reaching the Over-Temperature-

Protection (OTP) limit. The 34825 then turns off the power

MOSFET and sets the OTP_EN interrupt bit in the Interrupt

on again when the IC temperature falls below the OTP falling

temperature threshold, and the OVP_OTP_DIS bit is set. If

the above case happens repeatedly 7 times, the power

MOSFET will be permanently turned off until the accessory is

detached or the IC is reset.

The power MOSFET is turned off with a limited speed

under the OTP case to prevent a high overshoot voltage at

the VBUS pin.

OPERATION WITH ACCESSORIES

AUDIO ACCESSORY SUPPORTING REMOTE

CONTROLLER (R/C ACCESSORY)

Two ID resistors are designated for accessories with a

remote controller, as listed in Table 21. A typical accessory

with a remote controller is an audio headset that has a stereo

speaker, a micro phone, and a remote controller, as shown in

Figure 16. The five pins in the mini or micro-USB connector

are assigned in Figure 16. If some components are not

included in the accessory, the corresponding pins should be

left floating. For example, if the microphone is not included in

the stereo headset, VBUS pin should be left floating in the

headset.

The timing of the key pressing is shown in Figure 17. If a

key is pressed for a time less than 20 ms, the 34825 ignores

this key press. If the key is still pressed after 20 ms, 34825

starts a timer to count the time during which the key is

pressed. There are three kinds of key press conditions

according to the pressing time: error key press, short key

press, and long key press.

1. Error key press: if the key pressing time is less than

TKP, The 34825 ignores this key press.

2. Short key press: if the key pressing time is between

TKP and TLKP, the KP bit is set to inform the host IC.

The ADC result holds the key value. The INT outputs

low impedance when the key is released and returns to

a high impedance, due to the clearance of the KP bit

when the interrupt register is read.

3. Long key press: if the key pressing time is longer than

TLKP, the long key press bit LKP in the Interrupt register

is set to inform the host IC. The host IC needs to

respond to the key press immediately. The ADC result

holds the key value. When the key is released, the long

key release bit LKR in the Interrupt register is set to

interrupt the host IC again. The ADC Result register

still has the key value.

When such a accessory is attached, the 34825 can either

be forced into the Power Save mode or automatically enter

into the Power Save mode. This is controlled by the

AutoPSAVE bit in the Control register.

When AutoPSAVE = 1, if no activity is detected at the

SPK_L and SPK_R pins in 10 seconds, the 34825 enters the

Power Save mode automatically to minimize the quiescent

current. Upon detecting the activity in audio signal switches,

the 34825 returns to the Active mode. When AutoPSAVE = 0,

the host IC can control the mode of 34825 manually by

setting the PSAVE bit in the Device Mode register via I2C.

In the Power Save mode, the key pressing is monitored as

well.

34825 Datasheet(PDF) 22 Page - Freescale Semiconductor, Inc

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