1 TPA701 Audio Amplifier IC, BTL Operation

The TPA701 MSOP Audio Power Amplifier Evaluation Module

3.2.1TPA701 Audio Amplifier IC

The TPA701 audio amplifier IC is a CMOS device intended 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 2.5 V and 5.5 V) and deliver up to approximately 700 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. TPA701 Amplifier IC

4	_
	_	5
IN ±		5
3	+	OUT+
IN+	+
IN+
6
VDD
2	VDD/2
BYPASS	_	8
BYPASS
7
7	+	OUT±
		OUT±
GND
GND
1	Bias Control
SHUTDOWN	Bias Control
SHUTDOWN

The IC includes two separate internal amplifiers. The two amplifiers operate as mirror images of each other for increased power. BTL operation provides many benefits, including quadruple the output power of single-ended operation and no need for bulky output coupling capacitors. For more information, see the TPA701 amplifier IC data sheet, TI Literature Number SLOS229.

3.2.2BTL Operation

The 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.

3.2.3Module Gain

The TPA701 MSOP evaluation module has a set gain of 2. However, the gain can be adjusted to a maximum of 22 by changing the value of resistor R3 (Figure 3±3). Use the following equation to determine value of R3:

Gain +	±R3	2 for BTL

	R2

3-4

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