TA8155FNG 데이터 시트보기 (PDF) - Toshiba
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TA8155FNG Datasheet PDF : 17 Pages
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TA8155FG/FNG
Application Note
(1) PW SW
It is necessary to connect an external pull−down resistor with the terminal PW SW (pin(12)), in case that this IC
is turned on due to external noise etc.
(2) Mode SW
IC mode is determined by switch condition
of RED SW (pin(11)) and LINE SW (pin(15))
(Table.1)
H level: Bias current should be applied
to switch terminal more than 5µA.
L level: Bias voltage should be applied to
switch terminal from 0V to 0.3V.
Table.1 IC mode
REC SW
L
LINE SW
L
PB mode
(PB)
H
Radio mode
(BUF)
( ) : Operating amplifier.
H
MIC−REC
(BUF,MIC,REC)
Radio−REC mode
(BUF,REC)
The leak current flows through the terminal of REC SW (pin(11)) or LINE SW (pin(15)), in case that the
terminals connected with VCC line independently, even though this IC is off−mode (the terminal of PW SW
(pin(12)) is off−mode).
And it is necessary to connect an external pull−down resistor with the terminal REC SW (pin(11)) and LINE SW
(pin(15)), in case that this IC is turned on due to external noise etc.
(3) Playback amplifier
Output voltage of playback amplifier is determined by an external resistor R1 and Rf.
VO
(PRE)
=
VREF−∆V−Rf
(
∆V
R1
−
IB(NF)
)
∆V is an off−set voltage which is designed to 18mV.
In case that β of transistor is assumed 100, IB(NF) is flowed 0.2µA in Fig.1. And output voltage of playback
amplifier (pin (8),(9)) in Fig.1 is
VO (PRE) = 0.85V−0.018V− (330kΩ+13kΩ)
x ( 0.018V - 0.2µA) = 0.56(V)
18kΩ
Output voltage of playback amplifier should be fixed VCC / 2,
because playback amplifier get a enough dynamic range.
And current source of 20µA is operated except playback
mode, in order to reduce a pop sound in
swichover between playback on / off mode (Fig.2).
Fig.1 DC output voltage of
playback amplifier.
5
2006-04-12
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