Datasheet

L
P
L S
OUT
L
2
R
x V
R + 2 x R
P = for unclipped power
2 x R
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TPA3110D2PowerLimitFunction
Vin=1.13 Freq=1kHzRLoad=8WV
PP
PLIMIT =1.8VPout=5W
PLIMIT =3VPout=10W
PLIMIT =6.96VPout=11.8W
Vinput
TPA3110D2
www.ti.com SLOS528D –JULY 2009–REVISED JULY 2012
PLIMIT
The voltage at pin 10 can used to limit the power to levels below that which is possible based on the supply rail.
Add a resistor divider from GVDD to ground to set the voltage at the PLIMIT pin. An external reference may also
be used if tighter tolerance is required. Also add a 1μF capacitor from pin 10 to ground.
Figure 36. PLIMIT Circuit Operation
The PLIMIT circuit sets a limit on the output peak-to-peak voltage. The limiting is done by limiting the duty cycle
to fixed maximum value. This limit can be thought of as a "virtual" voltage rail which is lower than the supply
connected to PVCC. This "virtual" rail is 4 times the voltage at the PLIMIT pin. This output voltage can be used to
calculate the maximum output power for a given maximum input voltage and speaker impedance.
(1)
Where:
R
S
is the total series resistance including R
DS(on)
, and any resistance in the output filter.
R
L
is the load resistance.
V
P
is the peak amplitude of the output possible within the supply rail.
V
P
= 4 × PLIMIT voltage if PLIMIT < 4 × V
P
P
OUT
(10%THD) = 1.25 × P
OUT
(unclipped)
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