TDA8933B Datasheet, PDF(9/42 Page) NXP Semiconductors

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TDA8933B Datasheet, PDF (9/42 Pages) NXP Semiconductors – Class D audio amplifier

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NXP Semiconductors

TDA8933B

Class D audio ampliï¬er

This means that the device will not switch off completely, but remains operational at lower

output power levels. With music output signals, this feature enables high peak output

powers while still operating without any external heat sink other than the copper area on

the Printed-Circuit Board (PCB).

If the junction temperature still increases due to external causes the OTP shuts down the

ampliï¬er completely.

8.4.2 OverTemperature Protection (OTP)

If the junction temperature Tj > 155 Â°C the power stage will shut down immediately.

8.4.3 OverCurrent Protection (OCP)

The OCP can distinguish between an impedance drop of the loudspeaker and a

low-ohmic short circuit.

If an impedance drop causes the output current to exceed 2 A, e.g. due to dynamic

behavior of the loudspeaker, the ampliï¬er will start limiting the current above 2 A.

Therefore the current limiting feature will avoid audio interruption (audio holes) due to a

loudspeaker impedance drop.

If a fault condition causes the output current to exceed 2 A, like a short circuit between the

loudspeaker terminals or from the loudspeaker terminal to the supply lines or ground, the

ampliï¬er is switched off and a timer of 100 ms is started. The DIAG is set low for the ï¬rst

50 ms of the timer. The timer will keep the power stage disabled for at least 100 ms.

Every 100 ms the ampliï¬er will try to restart as long as the short circuit between the

loudspeaker terminals remains. The average power dissipation in the TDA8933B will be

low because the short circuit current will ï¬ow only during a very short time every 100 ms.

If a short circuit occurs between a loudspeaker terminal and the supply lines or ground,

the activated WP will keep the power stage disabled (no restart every 100 ms). Restart

will take place after removing this short.

8.4.4 Window Protection (WP)

The window protection protects the ampliï¬er against the following fault conditions:

â¢ During the start-up sequence, when pin POWERUP is switched from Sleep mode to

Mute mode. In the event of a short circuit at one of the output terminals to VDDP1,

VSSP1, VDDP2 or VSSP2 the start-up procedure is interrupted and the TDA8933B waits

for open circuit outputs. Because the check is done before enabling the power stages

no large currents will ï¬ow in the event of a short circuit.

â¢ When the ampliï¬er is shut down completely due to activation of the OCP or because

of a short circuit to one of the supply lines, then during restart (i.e. after 100 ms) the

window protection will be activated. As a result the ampliï¬er will not start up until the

short circuit to the supply lines has been removed.

8.4.5 Supply voltage protection

If the supply voltage drops below 10 V the UnderVoltage Protection (UVP) circuit is

activated and the system will shut down directly. This switch-off will be silent and without

pop noise. When the supply voltage rises above the threshold level the power stage is

restarted after 100 ms.

TDA8933B_1

Preliminary data sheet

Rev. 01 â 23 October 2008

9 of 42

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