max98400a Maxim Integrated Products, Inc., max98400a Datasheet - Page 18

• Manufacturer Part Number: max98400a
• Description: Stereo, High-power, Class D Amplifiers
• Manufacturer: Maxim Integrated Products, Inc.

The ICs offer eight pin-selectable gain settings, select-
able through the G1 and G2 pins.
The ICs feature overcurrent protection and two types of
thermal protection: thermal foldback and overtempera-
ture protection.
The ICs feature thermal foldback that helps prevent
unwanted thermal-shutdown events. If activated, ther-
mal foldback attenuates the stereo output signal once
the internal junction temperature exceeds +130NC.
Attenuation is applied proportionally as the junction tem-
perature (T
thermal-foldback mode is controlled by the TEMPLOCK
pin.
The ICs feature an overtemperature protection that dis-
ables the amplifier if the junction temperature exceeds
+165NC. Once the amplifier is disabled and the die tem-
perature has cooled by 20NC, the devices enable again
and resume normal operation.
When the output current reaches the current limit, 5A
(typ), the ICs disable the outputs and initiate a recovering
Stereo, High-Power, Class D Amplifiers
Table 2. Gain Selection
18
J
) exceeds the fixed +130NC threshold. The
Unconnected
Unconnected
Unconnected
GND
GND
GND
G1
V
V
V
S
S
S
Preamplifier Gain Setting
Overtemperature Protection
Overcurrent Protection
Thermal Foldback
Protection
Unconnected
Unconnected
Unconnected
GND
GND
GND
G2
V
V
V
S
S
S
sequence. The shutdown and recovering sequence is
repeated until the output fault is removed.
Traditional Class D amplifiers require an output filter
to recover the audio signal from the amplifier’s output.
The filters add cost, increase the solution size of the
amplifier, and can decrease efficiency and THD+N
performance. The traditional PWM scheme uses large
differential output swings (2 x V
causes large ripple currents. Any parasitic resistance in
the filter components results in a loss of power, lowering
the efficiency.
These ICs do not require an output filter. The devices
rely on the inherent inductance of the speaker coil and
the natural filtering of both the speaker and the human
ear to recover the audio component of the square-wave
output. Eliminating the output filter results in a smaller,
lower cost solution.
Because the frequency of the ICs’ output is well beyond
the bandwidth of most speakers, voice coil movement
due to the square-wave frequency is very small. For
optimum results, use a speaker with a series inductance
> 10FH. Typical 8I speakers exhibit series inductances
in the 20FH to 100FH range.
Applications Information
Filterless Class D Operation
GAIN SETTING
Reserved
DD
(dB)
16.7
20.1
23.3
26.4
29.8
32.9
13
9
peak-to-peak) and