TA0104A Datasheet, PDF (9/18 Pages) Tripath Technology Inc. – STEREO 500W (4Ω) CLASS-T DIGITAL AUDIO AMPLIFIER DRIVER USING DIGITAL POWER PROCESSING (DPPTM) TECHNOLOGY

Tripath Technology, Inc. - Technical Information
Overload
When logic low, the OVERLOADB pin indicates that the level of the input signal has overloaded the
amplifier and that the audio output signal is starting to distort. The OVERLOADB signal is active only
while an overload is present. The OVERLOADB signal can be used to control a distortion indicator
light or LED through a simple buffer circuit.
Mute
When a logic high signal is supplied to MUTE, both amplifier channels are muted (both high- and
low-side transistors are turned off) and a logic level high is output on the HMUTE pin. When a
logic level low is supplied to MUTE, both amplifiers are fully operational and a logic level low is
supplied on HMUTE. There is a delay of approximately 200 milliseconds between the de-
assertion of MUTE and the un-muting of the TA0104A.
Application Information
Amplifier Gain and Input Resistor Selection
The value of the input resistor, R_IN, is based on the required voltage gain, A_V, of the amplifier
according to:
A_V = 800 x10³/(R_IN + 5000)
where R_IN = Input resistor value in ohms.
Input Capacitor Selection
C_IN can be calculated once a value for R_IN has been determined. C_IN and R_IN determine the input low-
frequency pole. Typically this pole is set at 10 Hz. C_IN is calculated according to:
C_IN = 1/(2π x F_P)(R_IN + 5000)
where:
R_IN = Input resistor value in ohms.
F_P = Input low frequency pole (typically 10Hz).
DC Offset Adjust
While the DC offset voltages that appear at the speaker terminals of a TA0104A amplifier are typically
small, Tripath recommends that any offsets during operation be nulled out of the amplifier with a
circuit like the one shown connected to IN1 and IN2 in the Test/Application Circuit.
It should be noted that the DC voltage on the output of a TA0104A amplifier with no load in mute
mode is approximately 2.5V. This offset does not need to be nulled. The output impedance of the
amplifier in mute mode is approximately 10 KOhms. This means that the 2.5V drops to essentially
zero when a typical load is connected.
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TA104A – Rev. 3.1/06.00