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User manual for MA evaluation boards
MA2304DNS/MA2304PNS
Measurement methods
4
Measurement methods
Setting up a reliable measurement configuration for the MA2304DNS or the MA2304PNS takes a little more
effort than for linear amplifiers, and even "regular" switching amplifiers. This is mainly because the MA2304xNS
is a filterless amplifier, which means it does not require an external (usually expensive and bulky) LC filter to
remove switching residuals. The filterless application is enabled by the MERUS™ audio multilevel technique,
which ensures the switching residual is orders lower compared to "regular" switching amplifiers. For more
information on the multilevel switching technique, please refer to the datasheet.
To obtain reliable measurement results, the MA2304xNS devices require a separate external LPF in front of the
input stage of the audio analyzer. Most audio analyzers are bandwidth-limited at their input stage, which
means they cannot follow the rapid changes of the amplifier's output stage. This can result in inaccurate and
high THD+N measurements.
Figure 11
shows the recommended measurement setup. The setup shows a LPF stage (AUX-0025) in front of
the audio analyzer (APx525 with the serial interface I/O option installed). In this case the measurement setup
has been built around Audio Precision hardware, but this can also be some other audio analyzer hardware.
Please note that it is recommended to use a balanced input measurement configuration.
Audio Analyzer
Digital Serial
Bit Clock
Frame Clock
Data Out
Analog Input
ChA IN
ChB IN
Audio Precision APx525
Figure 11
Recommended audio measurement setup
User Manual
External Class-D Filter
ChA OUT
ChA IN
ChB OUT
ChB IN
Audio Precision AUX-0025
14
Device Under Test (DUT)
Serial I/O
I2S_SCK
I2S_WS
I2S_DI
BTL Ch0
22µH
OUT+
OUT-
BTL Ch1
OUT-
OUT+
22µH
MA2304xNS
V 1.0
2022-08-26
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