TA2021-100 ETC1 [List of Unclassifed Manufacturers], TA2021-100 Datasheet - Page 18

• Manufacturer Part Number: TA2021-100
• Description: STEREO 100W (4-ohm) CLASS-T DIGITAL AUDIO AMPLIFIER DRIVER USING DPP-TM TECHNOLOGY
• Manufacturer: ETC1 [List of Unclassifed Manufacturers]

T E C H N I C A L I N F O R M A T I O N
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 TA2021-100 would need to be implemented to detect these failures.
Output Filter Design
One advantage of Tripath amplifiers over PWM solutions is the ability to use higher-cutoff-
frequency filters. This means any load-dependent peaking/droop in the 20kHz audio band
potentially caused by the filter can be made negligible.
This is especially important for
applications where the user may select a 4-Ohm or 8-Ohm speaker. Furthermore, speakers are
not purely resistive loads and the impedance they present changes over frequency and from
speaker model to speaker model.
Tripath recommends designing the filter as a 2nd order, 80kHz LC filter. Tripath has obtained
good results with L
= 18uH and C
= 0.22uF.
F
F
The core material of the output filter inductor has an effect on the distortion levels produced
by a TA2021-100 amplifier. Tripath recommends low-mu type-2 iron powder cores because of
their low loss and high linearity.
Tripath also recommends that an RC damper be used after the LC low-pass filter. No-load
operation of a TA2021-100 amplifier can create significant peaking in the LC filter, which
produces strong resonant currents that can overheat the output MOSFETs and/or other
components. The RC dampens the peaking and prevents problems. Tripath has obtained good
results with R
= 33
and C
= 0.1uF.
D
D
It is highly recommended that the design process for a TA2021-100 amplifier include an analysis
of the interaction of intended speaker(s) with the LC filter and RC damper to ensure the
desired frequency response is attained. Component values for the LC filter and RC damper may
need to be altered from the Tripath suggestions to achieve the required response.
Grounding
To Be Supplied
Circuit Board Layout
Considerable care needs to be taken in the layout of the circuit board for a TA2021-100
amplifier. The high currents flowing through PCB traces and the inductive effects due to the
switching frequencies involved can cause large overshoot and undershoot voltages if care is not
taken. A general rule to follow is to keep the PCB trace of each signal path to/from each lead
of each output MOSFET as short as physically possible.
Certain circuit functions in a TA2021-100 amplifier cannot share PCB return paths with other
functions because of the resistive and inductive effects of the switching currents and
frequencies used. These so-called ‘Kelvin’ paths must each have a dedicated PCB trace from the
TA2021-100 to their destination. GNDKELVIN1 and GNDKELVIN2 should be treated as Kelvin
paths.
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