ICs for Audio Common Use
s
Technical Information (continued)
2.Application Note (continued)
AN5278
6) Internal DC mute pulse (during power OFF)
During power OFF, the decay response of the RF pin is being made use of internally, to generate an internal DC
mute pulse. The output DC level is made to fall quickly. As the output level falls, any transient noise that happens
prior to the input pin is effectively cut off from the IC. The residual electric charge in the large output capacitor (at
Pin8) is discharged into the IC internal path. By this manner, at the next start-up, the output will start from almost
0 V, and reduce the occurrence of shock noise.
Condition : V
CC
=
18 V, C
RF
=
100
µF,
C
NF
=
10
µF,
C
VCC
=
1000
µF.
Output
Pin8
Internal
DC mute
pulse
300 ms
7) Shock noise precaution
During power ON, to reduce the occurence of
“Shock”
noise, please be careful when selecting suitable capacitor
values for RF (Pin5) and NF (Pin6).
Recommendation :
−
1. NF
=
10
µF
*
2. NF
=
22
µF
*
RF
=
100
µF
to 330
µF
RF
=
220
µF
to 330
µF
* : Due to small NF capacitor, the low frequency cut-off is about 50 Hz.
* : Due to larger RF capacitor, the start-up time is longer, about 1 second.
9
PANASONIC [ PANASONIC SEMICONDUCTOR ]
