max98089 Maxim Integrated Products, Inc., max98089 Datasheet - Page 105

• Manufacturer Part Number: max98089
• Description: Low-power, Stereo Audio Codec With Flexsound Technology
• Manufacturer: Maxim Integrated Products, Inc.

The IC’s power limiter tracks the continuous power deliv-
ered to the loudspeaker and briefly mutes the speaker
amplifier output if the speaker is at risk of sustaining
permanent damage.
Loudspeakers are typically damaged when the voice coil
overheats due to extended operation above the rated
power. During normal operation, heat generated in the
voice coil is transferred to the speaker’s magnet, which
transfers heat to the surrounding air. For the voice coil
to overheat, both the voice coil and the magnet must
overheat. The result is that a loudspeaker can operate
above its rated power for a significant time before it heats
sufficiently to cause damage.
Table 25. Power Limiter Registers
REGISTER
0x44
BIT
7
6
5
4
2
1
0
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PWRTH
NAME
PWRK
Power Limiter Threshold
If the continuous output power from the speaker amplifiers exceeds this threshold,
the output is briefly muted to protect the speaker. The threshold is measured in watts
assuming an 8I load. VBAT must correctly reflect the voltage of SPKLVDD/SP-
KRVDD to achieve accurate thresholds.
Power Limiter Weighting Factor
Determines the balance between time constant 1 and 2 to match the dominance of
each time constant in the loudspeaker.
Power Limiter
Low-Power, Stereo Audio Codec
VALUE
VALUE
0x0
0x1
0x2
0x3
0x4
0x5
0x6
0x7
000
001
010
011
100
101
110
111
with FlexSound Technology
The IC’s power limiter includes user-programmable time
constants and power thresholds to match a wide range
of loudspeakers. Program the power limiter’s threshold to
match the loudspeaker’s rated power handling. This can
be determined through measurement or the loudspeak-
er’s specification. Program time constant 1 to match the
voice coil’s thermal time constant. Program time constant
2 to match the magnet’s thermal time constant. The time
constants can be determined by plotting the voice coil’s
resistance vs. time as power is applied to the speaker.
THRESHOLD
Power limiter
disabled
0.05
0.06
0.09
0.11
0.13
0.18
0.22
DESCRIPTION
(W)
T1 (%)
37.5
62.5
87.5
12.5
100
50
75
25
VALUE
0xA
0xB
0xC
0xD
0x8
0x9
0xE
0xF
MAX98089
T2 (%)
37.5
12.5
87.5
62.5
THRESHOLD
50
25
75
0
0.27
0.35
0.48
0.72
1.00
1.43
1.57
1.80
(W)