User Manual
27
V 1.1
2022-09-12
User manual for MERUS™ audio amplifier configurato
r
MA2304DNS/MA2304PNS
DSP flows
Figure 39
Output 0 configuration
This setting scales the left and right input signals by two such that their sum results in unity gain.
Requirements 2, 3 and 4: output power limiting and P
VDD
voltage
The goal for these requirements is to keep the loudspeaker RMS and peak power under control. Continuously
driving 5 W into the speaker is small enough that a heatsink is not required to keep the IC temperature below
the temperature warning.
The peak and RMS limiters of the MA2304DNS will then be configured to keep loudspeaker power (and
temperature) under control.
The continuous and peak power handling specifications from a speaker manufacturer are typically derived
from bandwidth-limited pink noise tests played for a specified duration. For larger speaker systems it is
common to adjust the amplifier power supply voltage and/or amplifier gain setting to match the speaker power
rating. In smaller speaker systems, intelligibility and loudness become important and, therefore, additional
techniques such as limiting and compression may be used to achieve this purpose.
To select a power supply voltage and/or amplifier gain, we first calculate the equivalent RMS and peak voltages
expected when the speaker is driven near its rated power levels.
First, let’s calculate the equivalent RMS voltage, V
1
, that corresponds to the continuous power handling, P
1
, as
previously provided in
𝑉
1
= √𝑃
1
× 𝑍
𝑛𝑜𝑚
[𝑉
𝑟𝑚𝑠
]
In this example, P
1
= 5 W and Z
nom
is 4
Ω
. V
1
is then 4.5 V
rms
.
Similarly, V
2
, the desired peak voltage, is calculated as follows:
𝑉
2
= √2𝑃
2
× 𝑍
𝑛𝑜𝑚
[𝑉
𝑝𝑒𝑎𝑘
]
V
2
is then 12.6 V
pk
. To be able to reproduce this voltage, a power supply greater than this voltage level is
recommended.
Looking at the table below, a P
VDD
of 15 V seems like a good choice.
Table 4
Amplifier gain
Parameter Description
pvdd_scale Recommended P
VDD
Value
Unit
G
dB
Amplifier gain in dB (V
rms
/FS)
00
10 V
16.5
dBV/FS
01
12 V
19
dBV/FS
10
15 V
21.2
dBV/FS
11
18 V
22.5
dBV/FS
To calculate the RMS and peak limiter thresholds, we use the corresponding G
dB
from the table above:
𝑇ℎ
1
= 20 log(𝑉
1
) − 𝐺
𝑑𝐵
[𝑑𝐵𝐹𝑆]
