TPA3121D2

SLOS537B – MAY 2008 – REVISED JANUARY 2014

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THERMAL PROTECTION

Thermal protection on the TPA3121D2 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 30°C. The device

begins normal operation at this point with no external system interaction.

PRINTED-CIRCUIT BOARD (PCB) LAYOUT

Because the TPA3121D2 is a class-D amplifier that switches at a high frequency, the layout of the printed-circuit

board (PCB) should be optimized according to the following guidelines for the best possible performance.

•

Decoupling capacitors—The high-frequency 0.1-

μF decoupling capacitors should be placed as close to the

PVCC (pins 1, 3, 10, and 12) and AVCC (pins 19 and 20) terminals as possible. The VBYP (pin 7) capacitor

and VCLAMP (pin 11) capacitor should also be placed as close to the device as possible. Large (220-

μF or

greater) bulk power-supply decoupling capacitors should be placed near the TPA3121D2 on the PVCCL and

PVCCR terminals.

•

Grounding—The AVCC (pins 19 and 20) decoupling capacitor and VBYP (pin 7) capacitor should each be

grounded to analog ground (AGND, pins 8 and 9). The PVCCx decoupling capacitors and VCLAMP

capacitors should each be grounded to power ground (PGND, pins 13, 14, 23, and 24). Analog ground and

power ground should be connected at the thermal pad, which should be used as a central ground connection

or star ground for the TPA3121D2.

•

Output filter—The reconstruction filter (L1, L2, C9, and C16) should be placed as close to the output terminals

as possible for the best EMI performance. The capacitors should be grounded to power ground.

•

Thermal pad—The thermal pad must be soldered to the PCB for proper thermal performance and optimal

reliability. The dimensions of the thermal pad and thermal land are described in the mechanical section at the

back of the data sheet. See TI Technical Briefs SLMA002 and SLOA120 for more information about using the

thermal pad. For recommended PCB footprints, see figures at the end of this data sheet.

For an example layout, see the TPA3121D2 Evaluation Module (TPA3121D2EVM) User Manual, (SLOU189).

Both the EVM user manual and the thermal pad application note are available on the TI Web site at

http://www.ti.com.

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