
TA2002F / FN
2002-10-30
5
Application Note
(1) PW SW
It is necessary to connect an external pull-down resistor with the terminal PW SW (pin (8)), in case that this IC
is turned on due to external noise etc.
(2) PW MUTE
The leak current flows through the terminal of PW MUTE (pin(9)), in
case that the terminal is connected with VCC line independently, even
though this IC is off-mode (the terminal of PW SW (pin(8)) is off-mode).
It is advised to connect R1 and C with the terminal of PW MUTE, to
reduce a pop sound in switchover between PW mute on / off. And it is
advised to connect R2, to shorten a switchover time from PW MUTE
off-mode to PW MUTE on-mode (see Fig.1). It is better that the
constants are R1≒R2≒100k, C≒1F at VCC = 3V.
As for the constants, select the optimum one depending on each a set
carefully.
Fig.1 PW mute circuit
reducing a pop
sound
(3) F / R SW
The terminal of F / R SW (pin(10)) should not be applied to higher voltage than V17 (RF OUT), because the
ripple filter circuit supplies the F / R SW circuit with power source. And in reverse mode, the terminal of F / R
SW should be connected with GND line through R3 (180~270k) , because the F / R SW circuit doesn't operate
normally. It is advised to connect an external capacitor (C3≒1F), in order to reduce a pop sound in switchover
between F / R mode (see Fig.2). As for the constants, select the optimum one depending on each a set carefully.
Fig.2 Internal equivalent circuit of F / R SW and PRE SW and the external circuits reducing a pop sound in
switchover.
9
VCC
R1
R2
C
24k
1k
100k
PRE
SW
18
330k
17
10
RF OUT
F / R SW
R4
C4
1k
48k
R3
C3