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Audio Amplifiers Forum
TAS5508C Fs change
My customer is using TAS5508C and Pre-Production stage now, and a qurious problem found.
1 They are sendng the initial register setting at every Power On,and no register setting done after the initial setting.
Note: /They use auto bank -- bank1( 32,44.1,48K) bank2( 88.2, 96K), bank3( 176.4,192K)
2 change the audio source ( CD 44.1K<=> DVD 48K) 10 times
3 PWM output (PWM8) does not come up 1time in the source change 10times.
I had suggested them to send " ALL OF the register setting "which is relative to fs change..( They did not send PWM8 setting because they don't
use biquad for PWM8)
4 Problem seems to resolved. They read- back register rom TAS5508C to compare the first( inital ) setting and the when problem found-.
The register 0x96~ 0x88 are changed. ( all zero not 00 80 00 00 00 00 )
< Question >
1 Please advise what is the cause of this issue. I think the change of 44.1K-48K is within same bank, and I believe i2c line of customer's set
is clean ( no glitch, noise found)
2 Do you think customer should set all of the register setting at the initial setting? Especially relative to fs?
Data sheet discribes as following..
3.5 Bank ControlsThe TAS5508C permits the user to specify and assign sample-rate-dependent parameters for biquad,loudness, DRC, and tone in one of three banks that can be manually selected or selected automaticallybased on the data sampling rate. Each bank can be enabled for one or more specific sample rates via I2Cbank control register 0x40. Each bank set holds the following values:• Coefficients for seven biquads (7 × 5 = 35 coefficients) for each of the eight channels (registers0x51–0x88)• Coefficients for one loudness biquad (register 0x95)• DRC1 energy and (1 – energy) values (register 0x98)• DRC1 attack, (1 – attack), decay, (1 – decay) values (register 0x9C)• DRC2 energy and (1 – energy) values (register 0x9D)• DRC2 attack, (1 – attack), decay, (1 – decay) values (register 0xA1)• Five bass filter-set selections (register 0xDA)• Five treble filter-set selections (register 0xDC)
Best Regads, and hope to hearing from you soon ( within 1week)
We should be getting you an answer soon!
Audio Applications Engineering Manager
Dallas, TX USA
I am sorry for the late response. I'll look at this first thing in the morning and get back with you.
Texas Instruments, Inc.
Q1 Please advise what is the cause of this issue. I think the change of 44.1K-48K is within same bank, and I believe i2c line of customer's set
Answer: I tried to duplicate the scenario you described above using an EVM and I could not get it to fail on PWM8.
When the source changes from CD to DVD, does the MCU write anything to TAS5508C? Does it mute and unmute? Even if the MCU does that, it should not cause the coefficients to change. It uses the same bank so it does not need to switch and bank switching does not change coefficients.
Was the register that read 00 00 00 00 ... changed to 00 80 00 00 ... before the Fs changed?
Does this happen to every unit or only a few?
Yes, the customer needs to set all the coefficients for each Fs for bank switching during initialization. The customer can update the coefficients later if it is needed.
Hello Tuan san,
Thank youfor your reply.
1 Thank you for your investigation. I will check customer's setting in detail again .
Please allow me to have a next question if necessary.
2 Thank you for your answer. I will tell to customer your advise.
Thanks and with my best regards
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