TFA9881_1104 Datasheet, PDF(12/32 Page) NXP Semiconductors – 3.4 W PDM input class-D audio amplifier

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TFA9881_1104 Datasheet, PDF (12/32 Pages) NXP Semiconductors – 3.4 W PDM input class-D audio amplifier

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NXP Semiconductors

TFA9881

3.4 W PDM input class-D audio amplifier

8.6.3 Supply voltage protection mechanisms (UVP and OVP)

UVP is activated, setting the outputs floating, if VDDP drops below the undervoltage

protection threshold, VP(uvp). This transition will be silent, without pop noise. When the

supply voltage rises above VP(uvp) again, the system will be restarted after 100 ms with

fclk = 6.144 MHz.

OVP is activated, setting the power stages floating, if the supply voltage rises above the

overvoltage protection threshold, VP(ovp). The power stages are re-enabled as soon as the

supply voltage drops below VP(ovp) again. The system will be restarted after 100 ms with

fclk = 6.144 MHz.

Note that a supply voltage > 5.5 V may damage the TFA9881.

8.6.4 OverCurrent Protection (OCP)

OCP will detect a short circuit across the load or between one of the amplifier outputs and

one of the supply lines. If the output current exceeds the overcurrent protection threshold

(IO(ocp)), it will be limited to IO(ocp) while the amplifier outputs are switching (the amplifier is

not powered down completely). This is called current limiting. The amplifier can

distinguish between an impedance drop at the loudspeaker and a low-ohmic short circuit

across the load or to one of the supply lines. The impedance threshold depends on which

supply voltage is being used:

â¢ In the event of a short circuit across the load or a short to one of the supply lines, the

audio amplifier is switched off completely. It will try to restart again after approximately

100 ms with fclk = 6.144 MHz. If the short-circuit condition is still present after this

time, this cycle will be repeated. Average dissipation will be low because of the short

duty cycle.

â¢ In the event of an impedance drop (e.g. due to dynamic behavior of the loudspeaker),

the same protection mechanism will be activated. The maximum output current is

again limited to IO(ocp), but the amplifier will not switch off completely (thus preventing

audio holes from occurring). This will result in a clipped output signal without artifacts.

TFA9881

Product data sheet

All information provided in this document is subject to legal disclaimers.

Rev. 2 â 1 April 2011

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