TAS5548: Modulation index limit register

user388725

Part Number: TAS5548
Other Parts Discussed in Thread: TAS5614A

Dear all,

If I select the lowest possible value for the modulation index (xFF in register x16, hence a modulation index of 87.40% for channels 1 and 2), can I expect a limitation of the output power and therefore of the THD?

If the question makes sense (I'm not sure it does), would you have any figures in the case where the power stage is a TAS5614A?

Thanks and regards,

Jean-Jacques

over 5 years ago

0 Shawn Zheng over 5 years ago

TI__Mastermind 24835 points

Hi Jean-Jacques,
The Modulation Limit Register is used to limit the duty-cycle on the output PWM. For class-d amplifier power stage, too high duty-cycle on the ouptut could cause the over-discharge on the bootstrap caps and then trigger the fault. Please find more explanation in this app note: www.ti.com/.../sloa259.pdf, which is for TPA31xx device but the principle is about the same.
It indeed limits the max linear output range a little, but the figure for THD is not available as far as I know.
Best regards,
Shawn Zheng

0 user388725 over 5 years ago in reply to Shawn Zheng

Prodigy 70 points

Thanks Shawn!
JJ

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TAS5548: Modulation index limit register