Datasheet Please read the Important Notice and Warnings at the end of this document V 1.0
www.infineon.com page 12 of 88 2018-07-17
8 Functional description
Multi-level modulation
The power stage of the MA12040P is a true multi-level switching topology. Each half-bridge is capable of delivering a
PWM output with three voltage levels, rather than the conventional two. The three-level half-bridges are each driven
with a two-phase PWM signal, so that the switching frequency seen at the PWM output is twice that of the individual
power MOSFET switching frequency.
For very low EMI in BTL configuration, the two half-bridges are operated in a complementary fashion (i.e. with 180⁰
phase shift), which removes common-mode PWM output content. This configuration is ideal for driving long speaker
cables without an output filter. Differentially, this modulation method drives the filter/load assembly with three PWM
levels.
For reduced power loss in the BTL configuration, the half-bridges can also be driven in a quadrature phase shifted
fashion (i.e. with 90⁰ phase shift). This provides a total of five PWM levels at the load, along with a quadrupling of
MOSFET switching frequency with respect to the differential PWM switching frequency. With this modulation scheme,
the MOSFET switching frequency can therefore be lowered, in order to decrease switching losses. The five-level
modulation scheme produces a common-mode voltage on the load wires, but with less high-frequency content
compared to conventional two-level BD modulation.
The multi-level switching topology of the MA12040P makes filterless operation viable, since the modulation schemes
ensure little or no idle losses in the speaker magnetic system.
For applications with stringent EMC requirements or long speaker cables, the MA12040P can operate with a very small
and inexpensive EMI/EMC output filter. This is enabled by the multiple PWM output levels and the frequency
multiplication seen on the PWM switching nodes. Notably, with the multi-level modulation of the MA12040P, there is
no tradeoff between idle power loss and inductor cost/size, which is due to the absence of inductor ripple current under
idle conditions in all configurations. Due to the high filter cutoff frequency, non-linearities of LC components have less
impact on audio performance than with a conventional amplifier. Therefore, the MA12040P can operate with
inexpensive iron-powder cored inductors and ceramic (X7R) filter capacitors with no significant audio performance
penalty.
Very low power consumption
The MA12040P achieves very low power loss under idle and near-idle operating conditions. This is due to the zero idle
ripple property of the multi-level PWM scheme, in combination with the programmable automatic reduction of
switching frequency at low modulation index levels; resulting in a state-of-the-art power efficiency at low and medium
output power levels.
For high output power levels, power efficiency is determined primarily by the on-resistance (Rds
on
) of the output
power MOSFETs. With music and music-like (e.g. pink noise) output signals with high crest factor, the reduced near-
idle losses of the MA12040P contribute to reducing power losses compared to a conventional amplifier with the same
Rds
on
. In most applications, this allows the MA12040P to run at high power levels without a heatsink.
Power Mode Management
The MA12040P is equipped with an intelligent power management algorithm which applies automatic power mode
selection during audio playback. In this state, the amplifier will seamlessly transition between three different power
modes depending on the audio level in order to achieve optimal performance in terms of power loss, audio performance
and EMI. Figure 8-1 shows an illustration of the basic power mode management. Alternatively, it is possible to manually
select the desired power mode for the MA12040P via the serial interface.
In both manual and automatic power mode selection, the power mode can be configured and set on-the-fly during
audio playback, with no audible artifacts. This makes it possible to optimize the target application to achieve the best
possible operating performance at all audio power levels.
During automatic power mode selection, the MA12040P can transition between power modes at programmable audio
level thresholds. The thresholds can be set via the serial control interface, by addressing the associated registers.