IRF IRAUDAMP6, User Manual, Page: 21 / 47

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IRAUDAMP6 REV 1
.0
For startup sequencing, +/-B supplies startup at different intervals. As +/-B supplies reach +5 V
and -5 V respectively, the analog supplies (+/-5 V) start charging and, once +B reaches ~16 V, V
CC
charges. Once –B reaches -20 V, the UVP is released and CSD and CStart start charging. Once
+/-5 V is established, the click-noise reduction circuit is activated through the SP MUTE control
signal. As CSD reaches two-thirds V
DD
, the Class D stage starts oscillating. Once the startup
transient has passed, SP MUTE is released (CStart reaches Ref1). The Class D amplifier is now
operational, but the preamp output remains muted until CStart reaches Ref2. At this point, normal
operation begins. The entire process takes less than three seconds.
Fig 14, Conceptual Shutdown Sequencing of Power Supplies and Audio Section Timing
Shutdown sequencing is initiated once UVP is activated. As long as the supplies do not discharge
too quickly, the shutdown sequence can be completed before the IRS20957 trips UVP. Once UVP
is activated, CSD and CStart are discharged at different rates. In this case, threshold Ref2 is
reached first and the preamp audio output is muted. Once CStart reaches threshold Ref1, the
click-noise reduction circuit is activated (SP MUTE). It is then possible to shutdown the Class D
stage (CSD reaches two-thirds V
DD
). This process takes less than 200 ms.
V
CC
-B
+B
+5 V
-5 V
CStart
CSD
UVP@-20 V
CSD= 2/3V
DD
CStart Ref1
CStart Ref2
Audio MUTE
SP MUTE
CHx_O
Class D shutdown
Time
Music shutdown