BM28723AMUV
13 Protection Function – continued
13.3 DC Voltage Protection for Speaker
When the DC voltage is applied to the speaker unintentionally, the embedded DC Voltage Protection circuit mute the
PWM output circuit for preventing the speaker from destruction.
Detecting condition - It will detect when MUTEX pin is set to high and PWM output Duty ratio=0% or 100% over
42ms (fs=48kHz). The PWM output immediately transition to the state of High-Z_low if detected,
and LSI does the latch.
Releasing method - Set MUTEX pin to low once for more than PWM stop time (Refer to P.19) and then return it back
to high.
Abnormal state release
PWM out locked duty=100% abnormal state.
OUT1P (25pin)
OUT1N (21pin)
OUT2P (20pin)
OUT2N (16pin)
PWM out: IC latches with High -Z_low state
t
.
Normal operation after released latch state
Speaker
BTL Output
(After LC Filter)
t
Soft start
Protection starts by a DC
voltage having been
applied to a speaker
more than 42ms
PWM stop time
ERRORX(13pin)
t
MUTEX(30pin)
Latch release
t
Figure 47. DC Voltage Protection in the Speaker Sequence
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