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LM48310: Does this part implement B-D modulation ?

Mike Burke1
Prodigy 20 points
Part Number: LM48310

The data sheet describes the output  uses a modulation scheme that provides for filter-less operation, but the modulation method is not described or identified. The data sheet does not show the time domain relationship between the two h-bridge outputs  in the way that higher TI power amplifiers do. It would be helpful to know this information for this part in particular and any filter-less audio amps TI produces, and to that end can it be assumed the filter-less Class-D is in general Class D with BD modulation in regards to TI offerings?

  • 0
    TI__Mastermind 18545 points

    Hello Mike, 

    Our team is looking into this thread and will respond as soon as possible. 

    Best Regards, 

    Justin Beigel

  • 0
    TI__Mastermind 19845 points

    Hi Mike,

    This part does use BD modulation. the "General Amplifier Function" section of the datasheet describes this modulations

    "With no signal applied, the outputs (VOUTA and VOUTB) switch between VDD and GND with a 50% duty cycle, in phase, causing the two outputs to cancel. This cancellation results in no net voltage across the speaker, thus there is no current to the load in the idle state. With the input signal applied, the duty cycle (pulse width) of the LM48310 outputs changes. For increasing output voltage, the duty cycle of VOUTAincreases, while the duty cycle of VOUTB decreases. For decreasing output voltages, the converse occurs. The difference between the two pulse widths yields the differential output voltage." 

    The time domain relationships of the outputs are shown in section 2.2 of this appnote https://www.ti.com/lit/an/slaa701a/slaa701a.pdf

    Best Regards,

    Arthur Brown