Texas Instruments TPA701 - Manual (Page 18)

The TPA701 MSOP Audio Power Amplifier Evaluation Module
3-4 Details
3.2.1 TPA701 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
5
OUT+
4
IN –
OUT–
8
3
IN+
_
_
+
+
7
2 VDD/2
VDD
GND
6
Bias Control
SHUTDOWN
1
BYPASS
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.
3.2.2 BTL 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.
3.2.3 Module 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 R
3:
Gain +
– R
3
R
2
2 for BTL