Tripath Technology, Inc. - Technical Information
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To minimize noise pickup and minimize THD+N, RFBC should be located as close to the
TA2022 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.
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CB provides high frequency bypassing for the bootstrap supplies. Very high currents are
present on these supplies.
CSW provides high frequency bypassing for the VN10 generator circuit. Very high currents
are present on these supplies.
C
SWFB filters the feedback signal (VN10FDBK) for the hysteretic VN10 buck converter. The
feedback signal is noise sensitive and the trace from CSWFB to VNN should be kept short.
DSW is the flywheel diode for the VN10 buck converter and prevents VN10SW(pin 5) from
going more than one diode drop below VNN.
In general, to enable placement as close to the TA2022, and minimize PCB parasitics, the capacitors
listed above 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.
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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. This was done
on the EB-TA2022 board.
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. This is
suggested by the routing on the Application/Test schematic, but, for space/layout reasons,
this was not fully implemented on the EB-2022.
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The modulator feedback resistors, RFBA and RFBB 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-TA2022 evaluation board for more information.
TA2022 Grounding
Proper grounding techniques are required to maximize TA2022 functionality and performance.
Parametric parameters such as THD+N, Noise Floor and crosstalk can be adversely affected if proper
grounding techniques are not implemented on the PCB layout. The following discussion highlights
some recommendations about grounding both with respect to the TA2022 as well as general “audio
system” design rules.
The TA2022 is divided into two sections: the input section, which spans pin 15 through pin 32, and
the output (high power) section, which spans pin 1 through pin 14. On the TA2022 evaluation board,
the ground is also divided into distinct sections, one for the input and one for the output. To minimize
ground loops and keep the audio noise floor as low as possible, the input and output ground must be
only connected at a single point. Depending on the system design, the single point connection may
be in the form of a ferrite bead or a PCB trace.
The analog grounds, pin 15 and pin 20 must be connected locally at the TA2022 for proper device
functionality. On the TA2022 evaluation board, Tripath has used an analog ground plane to minimize
the impedances between pin 15 and pin 20 as well as the other analog ground connections, such as
V5 supply bypassing, and feedback divider networks. The ground for the V5 power supply should
connect directly to pin 20. Additionally, any external input circuitry such as preamps, or active filters,
should be referenced to pin 20.
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TA2022 – KLI/1.2/07-04
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
