TA3020 Ver la hoja de datos (PDF) - Unspecified
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TA3020 Datasheet PDF : 27 Pages
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Tripath Technology, Inc. - Technical Information
Circuit Board Layout
The TA3020 is a power (high current) amplifier that operates at relatively high switching frequencies. The
output of the amplifier switches between VPP and VNN at high speeds while driving large 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 TA3020
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. Please refer to the TA3020 evaluation board document,
EB-TA3020, available on the Tripath website, at www.tripath.com.
The following components are important to place near either their associated TA3020 or output MOSFET pins.
The recommendations are ranked in order of layout importance, either for proper device operation or
performance considerations.
- The capacitors, CHBR, provide high frequency bypassing of the amplifier power supplies and will serve
to reduce spikes across the supply rails. Please note that both mosfet half-bridges must be
decoupled separately. In addition, the voltage rating for CHBR should be at least 150V as this
capacitor is exposed to the full supply range, VPP-VNN.
- CFB removes very high frequency components from the amplifier feedback signals and lowers the
output switching frequency by delaying the feedback signals. In addition, the value of CFB is different
for channel 1 and channel 2 to keep the average switching frequency difference greater than 40kHz.
This minimizes in-band audio noise. Locate these capacitors as close to their respective TA3020 pin
as possible.
- To minimize noise pickup and minimize THD+N, RFBC should be located as close to the TA3020 as
possible. Make sure that the routing of the high voltage feedback lines is kept far away from the
input op amps or significant noise coupling may occur. It is best to shield the high voltage feedback
lines by using a ground plane around these traces as well as the input section.
- CB, CSW provides high frequency bypassing for the VN10 and bootstrap supplies. Very high currents
are present on these supplies.
In general, to enable placement as close to the TA3020, and minimize PCB parasitics, the capacitors CFB, CB
and CSW should be surface mount types, located on the “solder” side of the board.
Some components are not sensitive to location but are very sensitive to layout and trace routing.
- To maximize the damping factor and reduce distortion and noise, the modulator feedback
connections should be routed directly to the pins of the output inductors. LO. Please refer to the EB-
TA3020This was done on the EB-TA3020 for additional information.
- The output filter capacitor, CO, and zobel capacitor, CZ, should be star connected with the load return.
The output ground feedback signal should be taken from this star point.
- The modulator feedback resistors, RFBA, RFBB, and RFBC, should all be grounded and attached to 5V
together. These connections will serve to minimize common mode noise via the differential
feedback. Please refer to the EB-TA3020 evaluation board for more information.
- The feedback signals that come directly from the output inductors are high voltage and high
frequency in nature. If they are routed close to the input nodes, INV1 and INV2, the high impedance
inverting opamp pins will pick up noise. This coupling will result in significant background noise,
especially when the input is AC coupled to ground, or an external source such as a CD player or
signal generator is connected. Thus, care should be taken such that the feedback lines are not
routed near any of the input section.
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TA3020 – KL Rev. 3.0/09.03
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