PA4201 PROTEC [Protek Devices], PA4201 Datasheet - Page 4

• Manufacturer Part Number: PA4201
• Description: PUNK POP-UP NOISE KILLER
• Manufacturer: PROTEC [Protek Devices]

PA4201-PUNK POP-UP NOISE KILLER -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 for which the
controller outputs are latched HIGH can be controlled by an external RC circuit. When the voltage
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 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.
SOFT Mute
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 SOFT mute 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 0.1 micro F and 0.5 µF. The reverse happens when the
MUTECONT signal is released. This operation is explained in detail in the Application Circuit section.
95020 REV.0 08/07
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