an5270 Panasonic Corporation of North America, an5270 Datasheet - Page 8

• Manufacturer Part Number: an5270
• Description: 4.3 W X 1 8ohm Power Amplifier With Volume Control And Tone Control
• Manufacturer: Panasonic Corporation of North America

AN5270
8
Power-on/off pop-noise elimination
Technical Information (continued)
In most TV applications, it is observed that there is a short period of delay from power-on to the onset of sound. The
purpose of power-on mute is to eliminate any unpleasant 'pop' noise (caused by transients) by effectively muting the
power amplifier. In this IC, an internal mute is incorporated at the instant of power-on and power-off. The length of
mute time depends on the value of the ripple filter condenser at Pin6. In the following diagram, the value of the
condenser connected to RF pin (Pin6) is 47 F.
(The above timing diagram is based on the evaluation circuit that is given in the product specification. Actual chasis
performance may differ due to differences in power supply and external components.)
The internal mute pulse will force the volume to minimum by grounding Pin4 momentarily. In most chasis, it is also
common to implement externally the audio defeat feature by forcing Pin4 to ground momentarily, for the purpose of
power-on/off as well as during channel switching. Should the internal mute be insufficient, it is recommended that
the external audio defeat be used.
V
Pin9
V
Pin1
Internal
mute-pulse
Volume
Pin4
Output
Pin8
CC2
CC1
170 ms
Fig. Power on/off typical timing characteristics of AN5270
470 ms
18 V
12 V
5 V
270 ms
220 ms
ICs for Audio Common Use
1.2 s