APA (audio power amplifier) outputs are sometimes connected to other voltage sources (APAs or power supplies), by design or mistake. If the connected source can force enough voltage at an APA output, it may damage the APA. Observing some simple limits can prevent this sort of damage.
- APA outputs must not be forced more than 0.3V above their positive power supply connection or more than -0.3V below their negative power supply connection. If these limits are exceeded, output FET body diodes can be forward biased and conduct current, and this may damage them.
- If a body diode conducts, it may not be damaged, but its current may flow to a power supply and increase power supply voltage. If a power supply is increased above an Absolute Maximum rating for an APA, this may damage the APA.
For single-supply APAs, power supply connections are VDD (or VCC) and ground.
For DirectPath(TM) headphone APAs with ground-references outputs, power supply connections can be different types.
- Supplies may be VDD and a negative supply, VSS, generated from VDD. The magnitude of VSS is usually less than VDD. This includes devices like TPA4411 and TPA6130A2.
- Supplies may be HPVDD, down-regulated from VDD, and HPVSS, the negative of HPVDD. HPVDD and HPVSS are set to limit available output power, to prevent hearing damage. This includes other devices in the TPA613xA2 family.
Data sheets generally list the power supplies and maximum ratings for them.
