STAC9721 Datasheet, PDF (33/48 Pages) List of Unclassifed Manufacturers – Stereo AC 97 Codec With Multi-Codec Option

SigmaTel, Inc.
Data Sheet
STAC9721
8. EXTENDED CODEC FUNCTIONALITY
8.1 Anti-Pop Circuitry
The STAC9721/23 provides an integrated output signal (APOP on pin 34) to aid in low-component-count
anti-pop implementations. An audible speaker "pop" can occur when the main power is applied to, or
removed from, the codec or audio output amplifier. In ac coupled systems, the speaker sided of the ac
coupling capacitor is shunted to ground through a transistor or FET; this prevents audible pops when the
system is powering on and off. A 10 µF capacitor on CAP1 provides a delay to hold-off power to the
output stages on power up. A 22 µF capacitor provides reserve power to sustain the output shunting
action until the power has been fully removed on power down. APOP is active logic high during shunting
operations; APOP is at logic low during normal operations.
9. AC TIMING CHARACTERISTICS (T_ambient = 25 °C, AVdd = DVdd = 5.0V or 3.3V ± 5%,
AVss=DVss+0V; 50pF external load)
9.1 Cold Reset
Figure 13. Cold Reset
RESET#
BIT_CLK
Tres_low
Trst2clk
Table 23. Cold Reset
Parameter
RESET# active low pulse width
RESET# inactive to BIT_CLK startup delay
Symbol Min Typ
Tres_low 1.0
-
Trst2clk 162.8 -
# denotes active low.
Max
-
-
Units
us
ns
33
04/07/00
04/07/00