T E C H N I C A L I N F O R M A T I O N
The modulator feedback resistors are:
R
R
FBA User specified, typically 1K
=
Ω
R
FBA * VPP
FBB
=
(VPP - 4)
R
FBA * VPP
R
A
FBC
=
4
R
FBC * (RFBA
R
FBB
)
+
V - MODULATOR
1
≈
+
R
FBA * RFBB
The above equations assume that VPP=|VNN|.
For example, in a system with VPPMAX=52V and VNNMAX=-52V,
FBA = 1kΩ, 1%
R
RFBB = 1.08kΩ, use 1.07kΩ, 1%
FBC = 13.0kΩ, use 13.3kΩ, 1%
R
The resultant modulator gain is:
13.3k Ω * (1.0k Ω 1.07k
)
+
Ω
A
V - MODULATOR
1 26.73V/V
+ =
≈
1.0k Ω * 1.07k Ω
Mute
When a logic high signal is supplied to MUTE, both amplifier channels are muted (both high- and
low-side transistors are turned off). When a logic level low is supplied to MUTE, both amplifiers are
fully operational. There is a delay of approximately 200 milliseconds between the de-assertion of
MUTE and the un-muting of the TA3020.
Turn-on & Turn-off Noise
If turn-on or turn-off noise is present in a TA3020 amplifier, the cause is frequently due to other
circuitry external to the TA3020. While the TA3020 has circuitry to suppress turn-on and turn-off
transients, the combination of the power supply and other audio circuitry with the TA3020 in a
particular application may exhibit audible transients. One solution that will completely eliminate turn-
on and turn-off pops and clicks is to use a relay to connect/disconnect the amplifier from the
speakers with the appropriate timing at power on/off. The relay can also be used to protect the
speakers from a component failure (e.g. shorted output MOSFET), which is a protection mechanism
that some amplifiers have. Circuitry external to the TA3020 would need to be implemented to detect
these failures.
DC Offset
While the DC offset voltages that appear at the speaker terminals of a TA3020 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.
20
TA3020, Rev 2.1, 01.01
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
