PA4201_09 PROTEC [Protek Devices], PA4201_09 Datasheet - Page 5

• Manufacturer Part Number: PA4201_09
• Description: Pop-Up-Noise Killer
• Manufacturer: PROTEC [Protek Devices]

THEORY OF OPERATION
STARTUP
During Startup, the Power supply ramps from 0V to VCC. This
time is usually in excess of 20ms. As soon
as this change in voltage is sensed, PUNK latches the Mute
Controller outputs to HIGH, thus “muting” the lines. This is the
Startup Operation (figure 1). The duration for which the
controller outputs are latched
HIGH can be controlled by an external RC circuit. When
the voltage at this RC pin reaches a certain threshold, the
mute controller releases the lines (Gate voltage is LOW)
and Normal Operation starts.
SHUTDOWN
During Shutdown, the reverse process happens. As the power
supply reaches the threshold on its way down, the mute
controller again latches the outputs to HIGH, thus “muting” the
lines (figure 2). This muting prevents unwanted signal spikes
from getting to the power amplifiers. However, for optimal
performance, it is suggested to mute the lines using the
MUTECONT signal before power down. This process will
ensure that the pop noise involved during shutdown is
diminished
SOFTMUTE
During normal operation, PUNK is in OFF state. But if there
arises a situation when the audio lines need
to be muted, the designer can do this by asserting the
MUTECONT signal to HIGH. This will initiate a
SOFTMUTE sequence (figure 3). When the MUTECONT
signal is asserted, the mute controller gradually ramps the
control voltages in a “SOFT” fashion so as to provide a soft
mute operation. The mute delay is fully controllable by the
designer by using an external capacitor at CEXT. Typical
values of CEXT are between 0.1μF and 0.5μF. The reverse
happens when the MUTECONT signal is released. This
operation is explained in detail in the Application Circuit
section.
95020 Rev.1. 06/09 PATENT PENDING
NOT FOR USE IN LIFE SUPPORT SYSTEMS
ANALOG PRODUCTS DIVISION
561 E. Elliot Road #175 Chandler, AZ 85225 Tel: [phone]. Fax: [phone]
www.protekanalog.com
Figure 2: Shutdown Pop-Noise Reduction
Figure 1: Startup Pop-Noise Reduction
Figure 3: SOFT mute operation
Pop-Up-Noise Killer
PA4201