Datasheet

TAS5112A
SLES094B - OCTOBER 2003 - REVISED JUNE 2008
www.ti.com
21
LAND PATTERN
PCB THERMAL
RESISTANCE
7 × 13 vias (5 × 10 mm) 2.2°C/W
5 × 11 vias (4 × 8 mm) 3.6°C/W
Thermal
Pad
8,20 mm
7,20 mm
3,90 mm
2,98 mm
Figure 17. Thermal Pad Dimensions for DCA
Package
CLICK AND POP REDUCTION
TI modulators feature a pop and click reduction system
that controls the timing when switching starts and stops.
Going from nonswitching to switching operation causes a
spectral energy burst to occur within the audio bandwidth,
which is heard in the speaker as an audible click, for
instance, after having asserted RESET LH during a
system start-up.
To make this system work properly, the following design
rules must be followed when using the TAS5112A back
end:
D The relative timing between the PWM_AP/M_x
signals and their corresponding VALID_x signal
should not be skewed by inserting delays,
because this increases the audible amplitude
level of the click.
D The output stage must start switching from a
fully discharged output filter capacitor. Because
the output stage prior to operation is in the
high-impedance state, this is done by having a
passive pulldown resistor on each speaker
output to GND (see System Configuration Used
for Characterization).
Other things that can affect the audible click level:
D The spectrum of the click seems to follow the
speaker impedance vs. frequency curve—the
higher the impedance, the higher the click
energy.
D Crossover filters used between woofer and
tweeter in a speaker can have high impedance
in the audio band, which should be avoided if
possible.
Another way to look at it is that the speaker impulse
response is a major contributor to how the click energy is
shaped in the audio band and how audible the click will be.
The following mode transitions feature click and pop
reduction.
STATE
CLICK AND
POP REDUCED
Normal
(1)
→ Mute Yes
Mute → Normal
(1)
Yes
Normal
(1)
→
Error recovery
(ERRCVY)
Yes
Error recovery → Normal
(1)
Yes
Normal
(1)
→ Hard reset No
Hard reset → Normal
(1)
Yes
(1)
Normal = switching