I came upon this nice calculator which seems very helpful if someone understands how to use it:
Power Dissipation vs Die Temp | Design Center | Analog Devices
unfortunately I don't clearly understand all of the parameters that need to be entered:
VOUT Load voltage? does it mean Vrms??
VGND Load ground? isn't that always "0" ??
RL Load resistance? talking about an amp's output BJTs or FETs do I have to enter speaker's load??
Power Dissipation vs Die Temp | Design Center | Analog Devices
unfortunately I don't clearly understand all of the parameters that need to be entered:
VOUT Load voltage? does it mean Vrms??
VGND Load ground? isn't that always "0" ??
RL Load resistance? talking about an amp's output BJTs or FETs do I have to enter speaker's load??
The load is assumed to be between the output to some other point 'load ground'. Normally it would be ground, 0V, but if the load is returned to some non-zero voltage, you can enter it here.
The rest should be self-explanatory. This is not about audio per sé, think of the load as anything loading the amp output. It should be in ohms. Output voltage should be in Vrms because RMS determines the power dissipation.
You could also have taken the time to read the instructions:
Instructions
This calculator computes die power dissipation and temperature for a linearly regulated output from quantities specified under "Parameters". It also computes power dissipated in an external load.
The model is of a linear push-pull output driving an external resistive load. Two common examples would be a digital bipolar output or a Class A amplifier. The voltage across the resistor, VOUT-VGND determines the current, IL, supplied by the output, which requires the internal driver dissipate IL * (V+-VOUT) or IL * (VOUT-V-) to supply the current linearly. Which rail supplies the current depends on whether the load current is positive or negative.
Total on-chip power, PTOTAL, is the sum of the power dissipated driving the load, plus the quiescent power, IQ * (V+-V-). The on-chip rise is equal to TA + thetaJA*PTOTAL. ThetaJA = ThetaJP (junction-to-package) + ThetaPA (package-to-ambient).
To use this calculator, simply enter the appropriate quantities in the parameter fields and then click "Calculate" or tab from field to field.
Jan
The rest should be self-explanatory. This is not about audio per sé, think of the load as anything loading the amp output. It should be in ohms. Output voltage should be in Vrms because RMS determines the power dissipation.
You could also have taken the time to read the instructions:
Instructions
This calculator computes die power dissipation and temperature for a linearly regulated output from quantities specified under "Parameters". It also computes power dissipated in an external load.
The model is of a linear push-pull output driving an external resistive load. Two common examples would be a digital bipolar output or a Class A amplifier. The voltage across the resistor, VOUT-VGND determines the current, IL, supplied by the output, which requires the internal driver dissipate IL * (V+-VOUT) or IL * (VOUT-V-) to supply the current linearly. Which rail supplies the current depends on whether the load current is positive or negative.
Total on-chip power, PTOTAL, is the sum of the power dissipated driving the load, plus the quiescent power, IQ * (V+-V-). The on-chip rise is equal to TA + thetaJA*PTOTAL. ThetaJA = ThetaJP (junction-to-package) + ThetaPA (package-to-ambient).
To use this calculator, simply enter the appropriate quantities in the parameter fields and then click "Calculate" or tab from field to field.
Jan
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I have read the instructions and the tutorial but still wasn't clear to me, I'm an amateur not even an experienced hobbyist.
Thanks a lot for the info.
Thanks a lot for the info.
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That calculator is for DC output only. The phrase "linearly regulated output" is the clue, together with the need for
a load voltage indicating DC coupling.
a load voltage indicating DC coupling.