
L
P
L
S
OUT
L
2
R
x V
R + 2 x R
P
=
for unclipped power
2 x R
÷
÷
÷
è
è
SLOS672 – OCTOBER 2010
www.ti.com
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:
RS is the total series resistance including RDS(on), and any resistance in the output filter.
RL is the load resistance.
VP is the peak amplitude of the output possible within the supply rail.
VP = 4 × PLIMIT voltage if PLIMIT < 4 × VP
POUT (10% THD) = 1.25 × POUT (unclipped)
REG_OUT Regulator
The TPA3117D2 has an integrated 5V regulator for driving external circuitry. Maximum output current is 30mA.
The regulator is always active when power is applied to the device. The SD pin does not disable operation.
Connect a series 10
Ω resister followed by a 2.2F capacitor to AGND before routing to the external circuitry.
When not used for powering external devices, a series 10
Ω resistor with 2.2 F of decoupling is still required.
PBTL Select
TPA3117D2 offers the feature of parallel BTL operation with two outputs of each channel connected directly. If
the PBTL pin (pin 11) is tied high, the positive and negative outputs of each channel (left and right) are
synchronized and in phase. To operate in this PBTL (mono) mode, apply the input signal to the RIGHT input and
place the speaker between the LEFT and RIGHT outputs. Connect the positive and negative output together for
best efficiency.
For normal BTL operation, connect the PBTL pin to local ground.
SHORT-CIRCUIT PROTECTION
TPA3117D2 has protection from overcurrent conditions caused by a short circuit on the output stage. Amplifier
outputs are switched to a Hi-Z state when the short circuit protection latch is engaged. After a typical delay of
250ms, the outputs will resume normal operation until another short occurs. It is not necessary to cycle pin SD to
restart the device operation after a short circuit event.
THERMAL PROTECTION
Thermal protection on the TPA3117D2 prevents damage to the device when the internal die temperature
exceeds 150°C. There is a ±15°C tolerance on this trip point from device to device. Once the die temperature
exceeds the thermal set point, the device enters into the shutdown state and the outputs are disabled. This is not
a latched fault. The thermal fault is cleared once the temperature of the die is reduced by 15°C. The device
begins normal operation at this point with no external system interaction.
It is not necessary to cycle SD terminal to restart device operation after a short circuit event.
FSEL FUNCTIONALITY
This terminal is used to select the switching frequency of the amplifier. In applications where more than one
device is needed, configure one device with FSEL = LOW (290kHz switching) and the other device with
FSEL = HIGH (390kHz switching).
16
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