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YMU757B
-22-
AP3
It is the bit that the power-down the reversal amplifier side of the speaker output part decline.
A reversal amplifier side is started after a VREF circuit and a non-reversal amplifier are started.
And, it depends, and pop noise occurrence can be restrained.
AP4
It is the bit that power-down DAC and the HP Volume part.
The attention point when the power-down moves.
Move from the condition that pronunciation surely stops for the power-down.
It is possible that the power-down a digital and an analog decline at the same time.
Be sure to mute FM Volume and HP Volume.
It is to restrain the noise when power going down.
The register which a digital part can't access during the power going down is as the following.
Index
Register functions
$00h
Note data
$10-2Fh
Tone data
$30h
Timbre allotment
$31h
Tempo data
$34h
IRQ Control
The attention point to cancel the power-down.
1 The time of 64×CLK_I is necessary before a digital part reverts to the normality after it is set
up in DP=0.
Be sure to do register access after you wait for this time.
2 The following are procedure that revert from the condition in analog whole power-down and
analog power supply off.
AP1 is set to 0. VREF stands up at the time of maximum 50ms.
Until VREF stands up, don’t set “0” to AP2-AP4.
AP2 is set to 0.
AP3, AP4 are set to 0 after minimum 10s.
An analog part becomes possible it moves.
AP4 is set to 1 when used only a speaker amplifier part(hands free phone)
AP2,3 are set to 1 when a speaker amplifier isn't used and only head phone is used.
And it is possible that electric current is further restrained.
Analog power supply OFF mode
Only while pronunciation stops, it is possible that an analog power supply is turned off.
Turn off an analog power supply after AP1, AP2, AP3 and AP4 are set to 1.
It has the possibility that pop noise occurs if it doesn't do so.