Audio Control FOUR.1i Specifications download pdf (Page 50)

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SHORT-CIRCUIT OUTPUT PROTECTION

JACK/HEADSET DETECTION

TLV320AIC34

SLAS538A – OCTOBER 2007 – REVISED NOVEMBER 2007

The high-power output drivers include additional circuitry to avoid artifacts on the audio output during power-on

and power-off transient conditions. The user should first program the type of output configuration being used in

page 0, register 14, to allow the device to select the optimal power-up scheme to avoid output artifacts. The

power-up delay time for the high-power output drivers is also programmable over a wide range of time delays,

from instantaneous up to 4 s, using page 0, register 42.

When these output drivers are powered down, they can be placed into a variety of output conditions based on

high-impedance state, and all power to the output stage is removed. However, this generally results in the output

nodes drifting to rest near the upper or lower analog supply, due to small leakage currents at the terminals. This

then results in a longer delay requirement to avoid output artifacts during driver power-on. In order to reduce this

required power-on delay, the TLV320AIC34 includes an option for the output terminals of the drivers to be weakly

driven to the VCM level at which they would normally when powered with no signal applied. This output VCM

level is determined by an internal band-gap voltage reference, and thus results in extra power dissipation when

the drivers are in power down. However, this option provides the fastest method for transitioning the drivers from

power down to full-power operation without any output artifact introduced.

The device includes a further option that falls between the other two — although it requires less power drawn

while the output drivers are in power down, it takes a slightly longer delay to power up without artifact than if the

band-gap reference is kept alive. In this alternate mode, the powered-down output driver terminal is weakly

driven to a voltage of approximately half the DRVDD1/2 supply level using an internal voltage divider. This

voltage does not match the actual VCM of a fully powered driver, but due to the output voltage being close to its

final value, a much shorter power-up delay time setting can be used and still avoid any audible output artifacts.

These output voltage options are controlled in page 0, register 42.

The high-power output drivers can also be programmed to power up first with the output level control in a highly

attenuated state, then the output driver automatically slowly reduces the output attenuation to reach the desired

output level setting programmed. This capability is enabled by default but can be enabled in page 0, register 40.

The TLV320AIC34 includes programmable short-circuit protection for the high-power output drivers, for maximum

flexibility in a given application. By default, if these output drivers are shorted, they automatically limit the

maximum amount of current that can be sourced to or sunk from a load, thereby protecting the device from an

overcurrent condition. In this mode, the user can read page 0, register 95 to determine whether the part is in

short-circuit protection or not, and then decide whether to program the device to power down the output drivers.

However, the device includes further capability to power down an output driver automatically whenever it goes

into short-circuit protection, without requiring intervention from the user. In this case, the output driver stays in a

power-down condition until the user specifically programs it to power down and then power back up again, to

clear the short-circuit flag.

The TLV320AIC34 includes extensive capability to monitor a headphone, microphone, or headset jack,

determine if a plug has been inserted into the jack, and then determine what type of headset/headphone is wired

to the plug. Figure 36 shows one configuration of the device that enables detection and determination of headset

type when a pseudodifferential (capless) stereo headphone output configuration is used. The registers used for

this function are page 0, registers 13, 14, 37, and 38. The type of headset detected can be read back from

page 0, register 13. Note that for best results, it is recommended to select a MICBIAS_x value as high as

possible, and to program the output driver common-mode level at a 1.35-V or 1.5-V level.

Product Folder Link(s): TLV320AIC34

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Audio Control FOUR.1i Specifications Page 50

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