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TLV320AIC33 strange output frequency

Other Parts Discussed in Thread: TLV320AIC33

Hi all, one of my customer is using the TLV320AIC33 to generat an audio signal at 48KHz from a 10MHz (using a PLL inside the Encoder).

at the HPROUT the signal is updated at 66KHz (it is possible to see the output of the DAC with signal steps at 66KHz).

The HPROUT is decoupled and then feeded in to amplifier.

Below the registers configuration.

Can you please help to understand the root source of the 66KHz ?

thanks,

Domenico

addr,value,mask
 0, x"00", x"01"
 1, x"00", x"80"
 2, x"44", x"FF"
 3, x"91", x"FF"
 4, x"24", x"FC"
 5, x"81", x"FF"
 6, x"C0", x"FC"
 7, x"0A", x"FF"
 8, x"D0", x"FF"
 9, x"40", x"FF"
10, x"00", x"FF"
11, x"01", x"0F"
12, x"00", x"FF"
13, x"00", x"9F"
14, x"00", x"C8"
15, x"30", x"FF"
16, x"30", x"FF"
17, x"FF", x"FF"
18, x"FF", x"FF"
19, x"FC", x"FF"
20, x"F8", x"FC"
21, x"80", x"F8"
22, x"FC", x"FF"
23, x"F8", x"FC"
24, x"F8", x"F8"
25, x"00", x"C0"
26, x"00", x"FF"
27, x"00", x"FF"
28, x"00", x"FF"
29, x"00", x"FF"
30, x"00", x"FF"
31, x"00", x"FF"
32, x"00", x"00"
33, x"00", x"00"
34, x"00", x"FF"
35, x"00", x"FF"
36, x"00", x"00"
37, x"C0", x"F8"
38, x"14", x"7E"
39, x"00", x"00"
40, x"00", x"FF"
41, x"00", x"FF"
42, x"00", x"FF"
43, x"50", x"FF"
44, x"50", x"FF"
45, x"00", x"FF"
46, x"00", x"FF"
47, x"00", x"FF"
48, x"00", x"FF"
49, x"00", x"FF"
50, x"00", x"FF"
51, x"09", x"FD"
52, x"00", x"FF"
53, x"00", x"FF"
54, x"00", x"FF"
55, x"00", x"FF"
56, x"00", x"FF"
57, x"00", x"FF"
58, x"00", x"FD"
59, x"00", x"FF"
60, x"00", x"FF"
61, x"E4", x"FF"
62, x"00", x"FF"
63, x"00", x"FF"
64, x"00", x"FF"
65, x"09", x"FD"
66, x"00", x"FF"
67, x"00", x"FF"
68, x"00", x"FF"
69, x"00", x"FF"
70, x"00", x"FF"
71, x"00", x"FF"
72, x"09", x"FD"
73, x"00", x"FF"
74, x"00", x"FF"
75, x"00", x"FF"
76, x"00", x"FF"
77, x"00", x"FF"
78, x"00", x"FF"
79, x"00", x"FD"
80, x"00", x"FF"
81, x"00", x"FF"
82, x"00", x"FF"
83, x"00", x"FF"
84, x"00", x"FF"
85, x"00", x"FF"
86, x"00", x"FD"
87, x"00", x"FF"
88, x"00", x"FF"
89, x"98", x"FF"
90, x"00", x"FF"
91, x"00", x"FF"
92, x"00", x"FF"
93, x"09", x"FD"
94, x"00", x"00"
95, x"00", x"00"
96, x"00", x"00"
97, x"00", x"00"
98, x"00", x"FD"
99, x"00", x"FB"
100, x"00", x"EE"
101, x"00", x"37"
102, x"02", x"FF"
103, x"00", x"00"
104, x"00", x"00"
105, x"00", x"00"
106, x"00", x"00"
107, x"00", x"00"
108, x"00", x"00"
109, x"00", x"00"
110, x"00", x"00"
111, x"00", x"00"
112, x"00", x"00"
113, x"00", x"00"
114, x"00", x"00"
115, x"00", x"00"
116, x"00", x"00"
117, x"00", x"00"
118, x"00", x"00"
119, x"00", x"00"
120, x"00", x"00"
121, x"00", x"00"
122, x"00", x"00"
123, x"00", x"00"
124, x"00", x"00"
125, x"00", x"00"
126, x"00", x"00"
127, x"00", x"00"
  • Hi, Domenyko,

    It is strange to have a 66KHz signal. But it could be related with the clock settings. I verified the registers configuration. The PLL values are configured as K = 9.8304, R = 1, P = 1. These values give a DAC_Fsref and ADC_Fsref = 48KHz. However, it seems that register 2 reduces the sampling rate (Fsref / 3). Could customer try configuring this register as 0x00?

    Thank you.

    Best regards,
    Luis Fernando Rodríguez S.
  • Hi Luis Fernando,

    the change of the value in the register 2 didn't produce any effect. The customer moreover requires the 8KHz data rate, the DAC receives samples from I2S at 8KHz.

    I've attached a screenshot of the scope which shows the strange stair behavior with steps at about 66KHz-70KHz update.

    It doesn't seem an absece of filter, the frequency update is odd.

    regards,

    Domenico

  • Hi, Domenico,

    Do you know if customer has the same issue with I2S samples at lower frequencies (1KHz for example)?

    If customer uses a lower sampling rate, then Fsref should be divided by 6 (48KHz / 6 = 8KHz). Could customer configure register 2 as 0xaa?

    Thank you.

    Best regards,
    Luis Fernando Rodríguez S.
  • Hi Luis Fernando,

    There wasn't any improvement changing the content of the register as per your suggestion.

    Now the customer is trying to use the direct R2 channel to start a debug and exclude error in the mixing portion.

    Any suggestions ?

    Regards,

    Domenyko

  • Hi, Domenico,

    I would recommend to try with I2S samples at different frequencies. Also, a constant I2S data could be useful to determine if this is related with the I2S data or the analog output.

    Best regards,
    Luis Fernando Rodríguez S.