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Q: The AGC and Limiter related questions of TPA2051
A customer raised some questions about TPA2051D3. Could you please help? Thank you.
There is description on page22 of TPA2051 datasheet. "Table 4 shows the selectable limiter levels for the Class-D amplifier when SPK_Gain (Register 5, bit 7) is LOW(6 dB)." Does it means that the limiter could only work when the SPK_Gain = 6dB? Could it work when SPK_Gain = 12dB?
Just would like to confirm that Limiter could apply on HP and SPK. And the AGC is only for SPK not HP, right? Thank you.
A: Re: The AGC and Limiter related questions of TPA2051
The speaker limiter works at both SPK_GAIN = 6 dB and SPK_GAIN = 12 dB. The limiter values are the same regardless of the SPK_GAIN setting. However, as noted in the datasheet the HP limiter values change with HP gain (see Table 5 "Typical Headphone Output Limiter Levels")
In the TPA2051D3 the AGC is a limiter-only function. The attack and release times for the limiter apply to both the HP limiter and the speaker limiter, so the AGC applies to both outputs. If both the speaker and HP outputs are enabled, the AGC determines output gain based on the speaker's limiter settings. If only the HP output is enabled, the AGC determines output gain based upon the HP output channel with the largest amplitude output.
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