Infineon MERUS MA12070P - Setting the Amplifier in PBTL Mode

User Manual 21 of 24 V 1.6
2021-11-09
MERUS™ audio amp HAT ZW
User manual - KIT_40W_AMP_HAT_ZW
Software setup
Table 3 shows suggested limiter threshold values according to the nominal speaker impedance and its
approximate DC resistance value using the official Raspberry Pi power supply. It is worth mentioning that these
values may vary, but they are a good starting point to know where the limiter threshold should be set.
Table 3 Suggested limiter threshold values vs. speaker impedance
Loudspeaker impedance
≈ DC resistance
Max. lim. threshold allowed
2 Ω
2 Ω
-16 dB
4 Ω
3.5 Ω
-13 dB
4 Ω
4 Ω
-11 dB
6 Ω
6 Ω
-9 dB
8 Ω
8 Ω
-7 dB
Optionally, if the audio source can’t reach full level for any reason, the volume can be increased accordingly.
However, in order to keep the booster output current below acceptable limits, the threshold should not be
modified.
4.6 Settng the amplifier in parallel bridge-tied load (PBTL) mode
The easiest way to set the board into PBTL mode is bu pulling down theRaspberry pi’s GPIO 8, which is
connected to the MESL0 pin of the MA12070P amplifier. To do this the following line should be added to the
config.txt file located at the root partition of the sd card:
gpio=8=op,dl
For more information on this functionality refer to the MA12070P datasheet.