Tripath Technology, Inc. - Technical Information
Mute
The mute pin must be driven to a logic low or logic high state for proper operation. The state of the
mute pin is “latched in” to minimize the effects of noise on this pin, which could cause the TA2022 to
switch state unintentionally. Controlling the mute pin with a push-pull output from a microcontroller, or
a physical switch between V5 and AGND, works well as both solutions have low impedance drive
capability. In some cases, it may be desirable to drive the mute pin with an alternative approach.
When the device is in mute, the pin must be “pulled low” via approximately 1kohm to overcome the
internal latch and change the TA2022 state (i.e. out of mute). When the device is not in mute, the
mute pin must be “pulled high” via approximately 2kohm to overcome the internal latch and change
the TA2022 state (i.e. into mute). Figure 3 shows a simple control circuit that buffers a Mute Control
signal that is not capable of driving the Mute pin of the TA2022 directly. When the Mute Control signal
is high, the Mute pin will be driven low and the TA2022 will be on. If the Mute Control signal is low,
the 2k resistor will pull the Mute pin high and the TA2022 will be muted.
V5
2k
TO MUTE
(Pin 24)
10k
MUTE
CONTROL
AGND
Figure 3: Low impedance drive for Mute Pin
To ensure proper device operation, including minimization of turn on/off transients that can result in
undesirable audio artifacts, Tripath recommends that the TA2022 device be muted prior to power up
or power down of the 5V supply. The “sensing” of the V5 supply can be easily accomplished by using
a “microcontroller supervisor” or equivalent to drive the TA2022 mute pin high when the V5 voltage is
below 4.5V. This will ensure proper operation of the TA2022 input circuitry. A micro-controller
supervisor such as the MCP101-450 from Microchip Corporation has been used by Tripath to
implement clean power up/down operation.
If turn-on and/or turn-off noise is still present with a TA2022 amplifier, the cause may be other circuitry
external to the TA2022. While the TA2022 has circuitry to suppress turn-on and turn-off transients,
the combination of power supply and other audio circuitry with the TA2022 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 that amplifier from the speakers with the appropriate
timing during power on/off.
TA2022 Output Capability
The TA2022 can output two channels at 100 watts each into a 4ohm load at 1% THD+N. The
maximum amplifier output power is determined by a number of factors including the TA2022 junction
temperature, the load impedance and the power supply voltage.
Tripath does not recommend driving loads below 4 ohm single ended as the amplifier efficiency will
be seriously reduced and the amplifier may prematurely current limit.
18
TA2022 – KLI/1.2/07-04
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
