Datasheet

TAS5548

SLES270 –NOVEMBER 2012

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6.2 Programming Energy Manager

Energy Manager related registers are 0xBA to 0xBE. 0xB2 is a 16 byte averaging filter (alpha filter) for

both satellite and sub channel. The scaling coefficients are 0xB3 to 0xBA that multiplies energy of each

channel with a scaling factor. The threshold registers are (0xBB, 0xBC, 0xBD and 0xBE) and 0x10 for the

results register.

Table 6-1. Energy Manager Status Register (x10)

D3 D2 D1 D0 FUNCTION

– – – 0/1 Energy below the low threshold for satellite channels

– – 0/1 – Energy above the high threshold for satellite channels

– 0/1 – – Energy below the low threshold for sub-woofer

channel

0/1 – – – Energy above the high threshold for sub-woofer

channels

So provision to read the whole byte and a way to clear the 4 LSB’s (one by one)

6.3 AM Avoidance Strategies

6.3.1 Frequency Scaling AM Avoidance

The AM avoidance strategy exploits the presence of the ASRC. The APLL output frequency is directly

varied by varying the multiplier ratio in the PLL loop. The dividers to generate clocks from the APLL are

fixed at their nominal division factor, so the result is that the internal sampling rate is changing accordingly.

The ASRC will adapt with this changing output rate (the internal sampling rate) and convert the incoming

sampling rates to this rate accordingly. The rest of the circuit does not change and operates normally, but

since the APLL output frequency is varied while the clock dividers are fixed, the PWM carrier frequency

becomes varied also, which is the goal of this AM avoidance strategy.

This shift in processing rate will effect time-domain digital processing, such as the EQ's and DRC's decay

values by the value in Freq_Error below.

Table 6-2. APLL/DAP/ASRC Clock Frequencies with New AM Avoidance Strategy

Input Prescal Feedba Internal # cycles ASRC Freq_Erro

Mode XTAL DCLK DAP CLK PWM rate

FS e ck SR per FS CLK r

Normal 8 - 192k 12288 4 64 196608 96 131072 1365.33 98304 384 0.00%

AM#1 8 - 192k 12288 4 62 190464 93 126976 1365.33 95232 372 -3.13%

AM#2 8 - 192k 12288 4 60 184320 90 12288 1365.33 92160 360 -6.25%

AM#3 8 - 192k 12288 4 58 178176 87 118784 1365.33 89088 348 -9.38%

AM#4 8 - 192k 12288 4 56 172032 84 114688 1365.33 86016 336 -12.50%

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