tda2075a Tripath Technology Inc., tda2075a Datasheet - Page 18

• Manufacturer Part Number: tda2075a
• Description: Stereo Class-t Digital Audio Amplifier Driver Using Digital Power Processingtm
• Manufacturer: Tripath Technology Inc.

T r i p a t h T e c h n o l o g y , I n c . - T e c h n i c a l I n f o r m a t i o n
DC Offset
While the DC offset voltages that appear at the speaker terminals of a TDA2075A amplifier are typically
small, Tripath recommends that all offsets be removed with the circuit shown in Figure 4. It should be
noted that the DC voltage on the output of a muted TDA2075A with no load is approximately 2.5V. This
offset does not need to be nulled. The output impedance of the amplifier in mute mode is approximately
10K: thus explaining why the DC voltage drops to essentially zero when a typical load is connected.
2.2uF, 25V
20.0k:
+
Input to TDA2075A
(DC Bias ~2.5V)
R
C
I
I
V5
470k:
470k:
10k:
0.1uF, 50V
Figure 4: Offset Adjustment
Mute
When a logic high signal is supplied to MUTE, both amplifier channels are muted (complementary
MOSFETs are turned off). When a logic level low is supplied to MUTE, both amplifiers are fully
operational. There is a delay of approximately 240 milliseconds between the de-assertion of MUTE and
the un-muting of the TDA2075A.
Turn-on & Turn-off Noise
If turn-on or turn-off noise is present in a TDA2075A amplifier, the cause is frequently due to other
circuitry external to the TDA2075A. The TDA2075A has additional circuitry, as compared to previous
Tripath amplifiers, which virtually eliminate any transients during power up and power down. While the
TDA2075A has sophisticated circuitry to suppress turn-on and turn-off transients, the combination of the
power supply and other audio circuitry with the TDA2075A in a particular application may exhibit audible
transients. It is recommended that MUTE is active (pulled high) during power up and power down to
minimize any audible transients caused by audio circuitry that precedes the TDA2075A.
Over-current Protection
The TDA2075A has over-current protection circuitry to protect itself and the output transistors from short-
circuit conditions. The TDA2075A senses the voltage across resistor R
to detect an over-current
S
condition. Resistor R
is in series with the load just after the low pass filter. The voltage is measured via
S
OCSP1 and OCSN1 for channel 1 and OCSP2 and OCSN2 for channel 2. The OCS* pins must be Kelvin
connected for proper operation. See “Circuit Board Layout” in Application Information for details.
When the voltage across R
becomes greater than V
(typically 0.5V), the TDA2075A will shut off the
S
TOC
output stages of its amplifiers. The occurrence of an over-current condition also causes the TDA2075A
Fault pin (pin 30) to go high. It is recommended that the Fault pin be connected externally to the mute pin
to mute the processor during an over-current condition. The Fault circuitry is an open drain configuration
and requires a pull-down resistor. The removal of the over-current condition returns the amplifier to
normal operation.
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