PA4101 PROTEC [Protek Devices], PA4101 Datasheet - Page 4

• Manufacturer Part Number: PA4101
• Description: PUNK with ?P Supervisor
• Manufacturer: PROTEC [Protek Devices]

THEORY OF OPERATION Audio Muting
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.
Timing Diagram Supervisor
95000 Rev. 0. 01/08
NOT FOR USE IN LIFE SUPPORT SYSTEMS
ANALOG PRODUCTS DIVISION
561 E. Elliot Road #175 Chandler, AZ 85225 Tel: [phone]. Fax: [phone]
V
RESET
CC
t
RP
V
RST
t
RD
V
RSTH
www.protekanalog.com
t
RP
Figure 2: Shutdown Pop-Noise Reduction
Figure 1: Startup Pop-Noise Reduction
Figure 3: SOFT mute operation
PUNK with µP Supervisor
PA4101
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