TA0105A Datasheet, PDF (15/29 Pages) Tripath Technology Inc. – STEREO CLASS-T DIGITAL AUDIO AMPLIFIER DRIVER USING DIGITAL POWER PROCESSING (DPPTM ) TECHNOLOGY

Tripath Technology, Inc. - Technical Information
connections are made to the TA0105A overcurrent sense pins or the traces, the overcurrent
sense circuit may prematurely trigger.
- 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. L_O. Please refer to the
RB-TA0105AThis was done on the RB-TA0105A for additional information.
- The output filter capacitor, C_O, and zobel capacitor, C_Z, should be star connected with the load
return. The output ground feedback signal should be taken from this star point.
- To minimize the possibility of any noise pickup, the trace lengths of IN1 and IN2 should be kept
as short as possible. This is most easily accomplished by locating the input resistors, R_I as
close to the TA0105A as possible. In addition, the offset trim resistor, R_OFB, which connects to
either IN1,or IN2, should be located close to the TA0105A input section.
TA0105A GROUNDING
Proper grounding techniques are required to maximize TA0105A 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 TA0105A as well as general “audio system”
design rules.
The TA0105A is divided into two sections: the input section, which spans pins 1-12 and pins 35-38 and
the output (high voltage) section, which spans pins 13 through pin 34. On the TA0105A 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 should not
be externally connected. They are already connected internally via a ferrite bead between pin 1 and pin
28. Additionally, any external input circuitry such as preamps, or active filters, should be referenced to
pin 1.
For the power section, Tripath has traditionally used a “star” grounding scheme. Thus, the load ground
returns and the power supply decoupling traces are routed separately back to the power supply. In
addition, any type of shield or chassis connection would be connected directly to the ground star located
at the power supply. These precautions will both minimize audible noise and enhance the crosstalk
performance of the TA0105A.
The TA0105A incorporates a differential feedback system to minimize the effects of ground bounce and
cancel out common mode ground noise. As such, the feedback from the output ground for each channel
needs to be properly sensed. This can be accomplished by connecting the output ground “sensing” trace
directly to the star formed by the output ground return, output capacitor, C_O, and the zobel capacitor, C_Z.
Refer to the Application / Test Circuit for a schematic description.
TA0105A THERMAL MANAGEMENT
The bottom of the TA0105A module is a metal plate and serves as a heat sink for the internal MOSFET
drivers. The temperature of this plate is directly related to the power dissipated in the output drivers. The
power dissipated is broken up into two main areas, the VN12 power, and the power needed to charge the
parasitic capacitances. These capacitances are internal to the MOSFET driver and the power to charge
these comes from VPP and flows to VNN. Thus, as the supply voltage difference VPP-VNN increases,
the amount of dissipation also increases.
Due to the increase in supply voltage, the TA0105A will run hotter than previous Tripath hybrids such as
the TA0104A. Thus, depending on system airflow, and the actual power supply voltages, it may be
necessary to attach an additional heat sink to the back plate or install a small fan to increase airflow
directly around the hybrid. Of note, the back plate has a high impedance connection to VNN.
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TA0105A – RW/ Rev. 2.2/05.05