Input

Signal

IN

TPA3131D2, TPA3132D2

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SLOS841B – SEPTEMBER 2013 – REVISED JANUARY 2015

Figure 20. Input AC Coupling

The input capacitors used should be a type with low leakage, like quality electrolytic, tantalum or ceramic. If a

polarized type is used the positive connection should face the input pins which are biased to 3 Vdc.

7.3.3 Start-up/Shutdown Operation

The TPA313xD2 employs a shutdown mode of operation designed to reduce supply current (Icc) to the absolute

minimum level during periods of nonuse for power conservation. The SDZ input terminal should be held high

(see specification table for trip point) during normal operation when the amplifier is in use. Pulling SDZ low will

put the outputs to mute and the amplifier to enter a low-current state. It is not recommended to leave SDZ

unconnected, because amplifier operation would be unpredictable.

For the best power-off pop performance, place the amplifier in the shutdown mode prior to removing the power

supply. The gain setting is selected at the end of the start-up cycle. At the end of the start-up cycle, the gain is

selected and cannot be changed until the next power-up.

7.3.4 PLIMIT Operation

The TPA313xD2 has a built-in voltage limiter that can be used to limit the output voltage level below the supply

rail, the amplifier simply operates as if it was powered by a lower supply voltage, and thereby limits the output

power. Add a resistor divider from GVDD to ground to set the voltage at the PLIMIT pin. An external reference

may also be used if tighter tolerance is required. Add a 1 µF capacitor from pin PLIMIT to ground to ensure

stability.

Figure 21. Power Limit Example

The PLIMIT circuit sets a limit on the output peak-to-peak voltage. The limiting is done by limiting the duty cycle

to a fixed maximum value. This limit can be thought of as a "virtual" voltage rail which is lower than the supply

connected to PVCC. This "virtual" rail is approximately 4 times the voltage at the PLIMIT pin. This output voltage

can be used to calculate the maximum output power for a given maximum input voltage and speaker impedance.

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