11.1 Independent Power Supplies

The TPA6120A2 consists of two independent high-fidelity amplifiers. Each amplifier has its own voltage supply, allowing the user to leave one of the amplifiers off, saving power, reducing the generated heat, and reducing crosstalk.

Although the power supplies are independent, there are some limitations. When both amplifiers are used, the same voltage must be applied to each amplifier. For example, if the left channel amplifier is connected to a ±12-V supply, the right channel amplifier must also be connected to a ±12-V supply. If the device is connected to a different supply voltage, it may not operate properly and consistently.

When the use of only one amplifier is preferred, it must be the left amplifier. The voltage supply to the left amplifier is also responsible for internal start-up and bias circuitry of the device. Regardless of whether one or both amplifiers are used, the V_CC- pins of both amplifiers must always be at the same potential.

To power down the right channel amplifier, disconnect the V_CC+ pin from the power source.

The two independent power supplies can be tied together on the board to receive their power from the same source.

11.2 Power Supply Decoupling

As with any design, proper power supply decoupling is essential. Decoupling prevents noise from entering the device via the power traces and provides the extra power the device can sometimes require in a rapid fashion, preventing the device from being momentarily current-starved. Both of these functions serve to reduce distortion, leaving a clean, uninterrupted signal at the output.

Bulk decoupling capacitors should be used where the main power is brought to the board. Smaller capacitors should be placed as close as possible to the actual power pins of the device. Because the TPA6120A2 has four power pins, use four surface mount capacitors. Both types of capacitors should be low ESR.