The TPA311 Audio Power Amplifier Evaluation Module
3.2.1TPA311 Audio Amplifier IC
The TPA311 audio amplifier IC is a CMOS device intended primarily for bridge-tied load (BTL) operation in battery-powered applications. It is supplied in a very small surface-mount package and has been designed to operate from low supply voltages (between approximately 2 V and 5.5 V) and deliver up to approximately 350 mW into an 8-Ω, BTL (Figure 3±4). Typical applications include portable phones, toys, games, and similar hand-held audio applications.
Figure 3±4. TPA311 Amplifier IC
| 4 | VDD/2 |
| _ |
| |
| IN | |
| | + |
| 2 | |
| Bypass | _ |
| |
| | + |
| 1 | |
| Shutdown | Bias |
| 3 | Control |
| SE/BTL | |
The IC includes two separate internal amplifiers and can operate in either the bridged-tied load (BTL) mode or the single-ended mode as selected by the SE/BTL pin. In the BTL mode, the two amplifiers operate 180° out-of-phase with each other for increased power. The speaker load is connected directly across VO+ and VO±, and neither line is connected to ground. BTL operation provides many benefits, including quadruple the output power of single-ended operation and no need for bulky output coupling capacitors. In the single-ended mode, one internal amplifier is turned off and the speaker load is connected between the VO+ terminal, through an output coupling capacitor, and system ground. For more information, see the TPA311 amplifier IC data sheet, TI Literature Number SLOS207.
3.2.2BTL Operation
To operate in the bridge-tied load output mode, the module SE/BTL control input terminal must be held low. The module output signal from OUT+ must go through the speaker load and be returned directly to OUT±, and NOT to system ground. This requires that the OUT± line be isolated not only from system ground, but also from the OUT± lines of any other amplifiers in the system. The platform provides such isolated output lines from the amplifier EVM sockets directly to separate left and right speaker connectors.
