KA3030D
Application Information
1. REFERENCE INPUT & MUTE CIRCUITS
Pin 23 can be used as a reference input terminal and a mute terminal.
• Reference input circuit
An external allowable reference voltage to pin 23 is normally 2.5V.
In general conditions, pin 23 is used as the reference input terminal and is good to be used between about
2V-6.5V.
• Mute circuit
The following represents the conditions when the external mute is permitted to pin 23.
Mute voltage
Min.
Mute on voltage[V]
-
Mute off voltage[V]
2
Typ.
Max.
Device condition
-
0.5
Mute
-
-
Operate
2. THERMAL SHUT-DOWN CIRCUIT
VREF BG
R1
R2
Mute control
Q
The setting voltage of VBE
VBE = VREF BG × R2 / (R1 + R2) = 400mV
Because the thermal coefficient of VBE(Q) is −2mV / 1°C and if TR Q reaches 175°C from its normal off state
(at 25°C), VBE for turning on Q becomes 400mV, and then Q turns on and the mute control circuit operates.
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