TS4984 Datasheet, PDF (18/29 Pages) STMicroelectronics – 2 x 1W Stereo audio power amplifier with active low standby mode

TS4984
Application Information
4 Application Information
The TS4984 integrates two monolithic power amplifiers with a BTL (Bridge Tied Load) output type
(explained in more detail in Section 4.1). For this discussion, only the left-channel amplifier will be
referred to.
Referring to the schematic in Figure 64, we assign the following variables and values:
V_in = IN-L
V_out1 = VO-L, V_out2 = VO+R
R_in = Rin-L, R_feed = Rfeed-L
C_feed = Cfeed-L
Figure 64: Typical application schematic - left channel
Cfeed = Cfeed-L
VCC
Rfeed = Rfeed-L
Cs
1u
Input L Cin = Cin-L
Vin- = IN-L
-
Rin = Rin-L
GND
Vin+= IN+L ₊
Standby
Bypass
Cb
1u
Bias
TS4984
-
AV = -1
+
Vout 1= VO-L
RL
Vout 2 = VO+L
4.1 BTL configuration principle
BTL (Bridge Tied Load) means that each end of the load is connected to two single-ended output
amplifiers. Thus, we have:
Single-ended output 1 = V_out1 = V_out (V),
Single-ended output 2 = V_out2 = -V_out (V), V_out1 - V_out2 = 2V_out (V)
The output power is:
P_out
=
(_{---2----V----o---u----t--R----M----S----})_---2-
R_L
For the same power supply voltage, the output power in a BTL configuration is four times higher than the
output power in a single-ended configuration.
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