ADAU1761 output power to headphone
Hi ADI's
I have a question about the DAC TO HEADPHONE / EARPIECE OUTPUT power of the ADAU1761.
On page 8 of the datasheet, it is shown below.
(Po = 10.6 mW when AVDD = 3.3 V, 32ohm load)
And looking at Figure 9 on page 17, it looks like about 15mW. (when 32ohm load)
What is the difference between the two data?
Question 1. What is the maximum output power when using AVDD = 3.3V, 32ohm load?
2. How much is the output when using 41ohm output?
Thank you
Audio Signal Processors
SigmaDSP Audio Processors
adau1761
Hello Andrew,
The specifications in the tables are derived from a much more stringent requirements and to cover all silicon skews with a margin added as a guard band to assure all parts will meet the specifications. The graphs in the Typical Performance Characteristics section are not as precise and are to be used as an approximation to see what the general behavior may be. So refer to the table for the guaranteed specifications. From the graphs it appears that most devices will exceed the 10.6mW specification listed in the table.
I do not have any data for other loads. The characterization was done only with a few loads and this was done a long time ago. The power output at 32 ohms is roughly half of the output at 16 ohms. So it is reasonable to assume that the power output would be half again at 64 ohms of load.
So 10.6 mW at 32 ohms
I am estimating it would be 5.3mW at 64 ohms.
Since 41 ohms is ~1/3 of the difference between 32 and 64, It is reasonable to assume the power output would also be 1/3 of the difference. This would be 1.77 so I am estimating that the power out at 41 ohms would be expected to be around 10.6-1.77= 8.83mW approximately.
Dave T
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