TECHNICAL INFORMATION

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TA2020-020, Rev. 4.0, 09.00

Application Information

Circuit Board Layout

The TA2020-020 is a power (high current) amplifier that operates at relatively high switching

frequencies. The outputs of the amplifier switch between the supply voltage and ground at high

speeds while driving high currents. This high-frequency digital signal is passed through an LC low-

pass filter to recover the amplified audio signal. Since the amplifier must drive the inductive LC

output filter and speaker loads, the amplifier outputs can be pulled above the supply voltage and

below ground by the energy in the output inductance. To avoid subjecting the TA2020-020 to

potentially damaging voltage stress, it is critical to have a good printed circuit board layout. It is

recommended that Tripath’s layout and application circuit be used for all applications and only be

deviated from after careful analysis of the effects of any changes.

The figures below are the Tripath TA2020-020 evaluation board.

Some of the most critical

components on the board are the power supply decoupling capacitors. C674 and C451 must be

placed right next to pins 22 and 19 as shown. C673 and C451B must be placed right next to pins

25 and 28 as shown. These power supply decoupling capacitors from the output stage not only

help reject power supply noise, but they also absorb voltage spikes on the VDD pins caused by

overshoots of the outputs of the amplifiers. Voltage overshoots can also be caused by output

inductor flyback during high current switching events such as shorted outputs or driving low

impedances at high levels.

If these capacitors are not close enough to the pins, electrical

overstress to the part can occur, possibly resulting in permanent damage to the TA2020-020.

B