STA304

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5.0 DDX OUTPUT SWITCHING

The 5 DDX output (L,R,SL,SR,LFE) are ternary modulated PWM, designed to drive directly STA50X power

bridge ICs or any custom discrete power. The PWM output frame is delayed from channel to channel in order

to reduce the crosstalk at the stereo STA50X device at low audio dynamics. The PWM order in the STA304 is:

–L

–LS

–R

–RS

with 32 ticks (of master clock) or ~640ns between the beginning of each PWM frame (frame period is ~2.6usec).

The LFE PWM signal is independently generated (synchronous with LS PWM output), because it is intended to

be used alone on a mono-configured STA50x IC (no crosstalk issues).

In this way the low-modulated level PWM signal of different channels switches when the others are at zero level,

so when the output power is in dump state (both terminals of the speaker loads are connected to ground), caus-

ing no noise cross-injection.

Best performances are obtained when only front channels (L/R) or rear channels (SL/SR) are fed to a single

STA50X device, because the PWM frames of L an R have the maximum distance of ~1.3usec (same for SL and

SR).

Of course crosstalk is anyway removed with a good power supply design/layout for STA50x ICs (low impedance

stage and low inductance loop between powerVDD and GND). See application notes for more details