SA1469XH
4) When the voltage of the mute pin is above 2V, the mute circuit is stopped and the output circuit is operated
normally.
5) If the chip temperature rises above 175°C, then the TSD (Thermal Shutdown) circuit is activated and the
output circuit is muted.
2. TSD (THERMAL SHUTDOWN)
VREF
Output Driver
Bias
R1
R2
Qn
1) The V
is the output voltage of the band-gap-referenced biasing circuit and acts as the input voltage of the
REF
TSD circuit.
2) The base-emitter voltage of the TR, Qn is designed to turn-on at below voltage.
V
BE
=V
* R2/(R1+R2)=460mV
REF
3) When the chip temperature rises up to 175°C, then the turn-on voltage of the Qn would drop down to 460mV.
(Hysteresis: 25°) and, the Qn would turn on so the output circuit will be muted.
3. OP-AMP
OP-Amp is integrated in the IC for user convenuence.
OPIN(+)
OPOUT
OPIN(-)
Pins 14, 15 and 16 may be left open when the operational amplifier is not used.
4. DRIVER
1) The voltage, V , is the reference voltage given by the BIAS voltage of the pin # 23.
REF
2) The input signal through the pin # 3 is amplified by 13K/10K times and then fed to the level shift.
3) The level shift produces the current due to the difference between the input signal and the arbitrary reference
signal. The current produced as +ΔV and -ΔV is fed into the driver buffer.
4) Driver buffer operates the power TR of the output stage according to the state of the input signal.
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
REV:1.4
2008.07.23
Http://www.silan.com.cn
Page 5 of 11
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