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[FAQ] TAS2563: How can I read the resistance of the speaker, Re, from the devices registers?

Part Number: TAS2563

I wish to use the Re value measured by TAS2563 externally. How can I get this value from the device?

where is Re located In the devices registers?

how do I read the value of Re from the device?

once the data has been read how to I convert it into a decimal ohm value?

what is the expected value of Re after the device is powered up? what is its value in tuning mode?

how does this value change while playing audio? how does it change when playing silence?

Regards,

Arthur Brown

• Hi,

The value of Re is located in device Book 100, page 2, registers 72 to 75.

The data in these registers can be read using the following script.

To convert this 32 bit hexadecimal value into a decimal ohm value you must

1) Transform 32 bit value from Hex to Dec

2) Then take value as floating point by dividing by 2^31

3) Finally take into 5.X format by multiplying by 16

Alternatively the attached excel document can perform this calculation

Re_calculator.xlsx

After device is powered up the value for register 72 to 75 will be 00 00 00 00. After entering tuning mode the Re value will be the Hex equivalent of the Re found during speaker characterization.

While playing audio the Re value will change. Most of the change in Re occurs due to heating of the voice coil.
During silence the Re value will remain unchanged as the device is not measuring Re. It is saved as the last value measured while playing audio. Unlike the impedance measured during speaker characterization there will be no peak in Re at the characterized resonance frequency of the speaker. Re is measured in such a way that only the DC resistance is observed.

For additional information on how TAS2563 measures Re please see section 4.1 in: SmartPA Speaker Protection Algorithm

Regards,

Arthur Brown