RT5509 Datasheet, PDF (25/58 Pages) Richtek Technology Corporation – Speaker Amplifier with Speaker Protection

Volume Control
The volume control can be set from 127.5dB to 0dB,
with step = 0.5dB. The control timing is illustrated as in
Figure 18. When a new gain is set by I²C, the hardware
will change from the original setting in step of 0.5dB/∆T,
where ∆T is the step size with the following options :
∆T = 4, 8, 16, 32, 64 samples, or ∆T = 0 stands for no
RT5509
ramping up / down is applied.
When mute mode is set by I²C or detected by hardware,
the volume setting is overruled, but the original gain
setting is kept in hardware, allows to be recovered to
the original state.
Volume control can be bypassed by register.
Gain (dB)
G_new
G_old
0.5dB
Time (spls)
∆T
Figure 18. Volume Control Timing Graph
The threshold is normalized to 1 is passed to speaker
protection which equals to :
ClipThres (normalized) = ^{5 - (VBCPS - VBAT )  CPSLP}
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ClipThres (normalized) equals to 1 if signal is small and
never reaches to the threshold. When signal is large
and is clipped by this threshold, ClipThres (normalized)
will be sent to speaker protection block.
If battery voltage returns to a hysteresis level,
ClipThres will increase by a rate of CLIPRR to a certain
level which is defined by VBCPS, CPSLP and VBAT.
As ClipThres increases, speaker protection will also
increase its gain to let the signal return to its original
level. The battery voltage hysteresis can bet set via
BVHYS at register 0x0B.
Copyright © 2017 Richtek Technology Corporation. All rights reserved.
DS5509-00 August 2017
is a registered trademark of Richtek Technology Corporation
www.richtek.com
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