|TPA3002D2||9-W STEREO CLASS-D AUDIO POWER AMPLFIER WITH DC VOLUME CONTROL|
|TPA3002D2 Datasheet PDF : 41 Pages |
SLOS402C − DECEMBER 2002 − REVISED JANUARY 2004
The TPA3002D2 employs a shutdown mode of operation designed to reduce supply current (ICC) to the
absolute minimum level during periods of nonuse for power conservation. The SD input terminal should be held
high (see specification table for trip point)during normal operation when the amplifier is in use. Pulling SD low
causes the outputs to mute and the amplifier to enter a low-current state, ICC(SD) = 10 µA. SD should never be
left unconnected, because amplifier operation would be unpredictable.
POWER-OFF POP REDUCTION
For the best power-off pop performance, the amplifier should be placed in the shutdown mode prior to removing
the power supply voltage.
Another method to reduce power-off pop can be implemented in the hardware. A 100-µF − 150-µF capacitor
can be added to the AVDD terminal in parallel with the 100-nF capacitor shown in Figure 29. The additional
capacitance holds up the regulator voltage for a longer period of time and results in smaller power-off pop.
USING LOW-ESR CAPACITORS
Low-ESR capacitors are recommended throughout this application section. A real (as opposed to ideal)
capacitor can be modeled simply as a resistor in series with an ideal capacitor. The voltage drop across this
resistor minimizes the beneficial effects of the capacitor in the circuit. The lower the equivalent value of this
resistance the more the real capacitor behaves like an ideal capacitor.
The TPA3002D2 has short circuit protection circuitry on the outputs that prevents damage to the device during
output-to-output shorts, output-to-GND shorts, and output-to-VCC shorts. When a short-circuit is detected on
the outputs, the part immediately disables the output drive. This is a latched fault and must be reset by cycling
the voltage on the SD pin to a logic low and back to the logic high state for normal operation. This will clear the
short-circuit flag and allow for normal operation if the short was removed. If the short was not removed, the
protection circuitry will again activate.
The trip-point for the short-circuit protection is nominally set at 8 A. However, this trip point can vary with PCB
layout and the separation of AVCC and PVCC. It is important to connect the AVCC pin as close as possible to
all of the PVCC pins with a wide (>20 mils) trace. This minimizes the inductance between the two pins and allows
the short-circuit protection to trip at the nominal current. If the inductance between these two pins is large, the
short-circuit protection may inadvertently trip when drive low impedance loads into heavy clipping.
Thermal protection on the TPA3002D2 prevents damage to the device when the internal die temperature
exceeds 150°C. There is a ±15 degree 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
20°C. The device begins normal operation at this point with no external system interaction.
THERMAL CONSIDERATIONS: OUTPUT POWER AND MAXIMUM AMBIENT TEMPERATURE
To calculate the maximum ambient temperature, the following equation may be used:
TAmax = TJmax – ΘJAPDissipated
where: TJmax = 150°C
ΘJA = 19°C/W
(2-Layer PCB, 5 sq. in. copper, see Figure 38)
To estimate the power dissipation, the following equation may be used:
PDissipated = PO(average) x ((1 / Efficiency) – 1)
Efficiency = ~85% for an 8-Ω load
= ~75% for a 4-Ω load
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