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TAS2781EVM: TAS2781 Frequency Reponse of PWR_MODE3

Simon Yuh
Prodigy 80 points
Part Number: TAS2781EVM
Other Parts Discussed in Thread: TAS2781

Dear sirs, 

I'm using the TAS2781 EVM, there is a question about ultrasound mode. (PWR_MODE3)

The frequency reponse of 20Hz ~ 40kHz with PWR_MODE3, Fs = 96k, show as below (Which is capture from TAS2781 Datasheet)

But I measure TAS2781 EVM with APx525 + AUX0025 as the same condition in datasheet, I can not get the same result as above , please check the picture my measurement as below.

The frequency response in 20kHz ~ 40kHz seems something setting issue ?

PVDDH=18V, PVDDL=5V, Power=1W, Fs=96kHz

I'm using the PurePath Console direct I2C to settle up the TAS2781, the command what I use are getting from TAS2781 datasheet 10.5 Initial Device Configuration - PWR_MODE3

Is there anything else I need to configure for this mode?

  • 0
    TI__Guru* 95175 points

    Hi Simon,

    Perhaps this is due to the filter you're using? AUX0025 has passband of 20-20kHz. You may need something like AUX-0040: https://www.ap.com/analyzers-accessories/accessories/aux-family-switching-amplifier-measurement-filters/

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 80 points

    Hi Ivan, 

    Thank you for your support.

    I try to use another Audio Precision, and measure the above condition again, I still can not get the datasheet's frequency response. (overthan +/-1dBrA, 20Hz~40kHz)

    Please check my TAS2781's FR result as below :

    In order to figure out the root cacuse, I pick up another amplifier (not TAS2781), and use the same AP's setting, I can get the frequency responce like below diagram (+/-0.6dBrA, 20Hz ~ 40kHz), so I don't think the AP's filter or my test condition was wrong. Can you help to figure it out ? 

  • 0 in reply to Simon Yuh
    TI__Guru* 95175 points

    Hi Simon,

    I'll double check on my side and give you a step-by-step procedure on how to configure the device for this test. I may have updates later today or by tomorrow.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    TI__Guru* 95175 points

    Hi Simon,

    I think I could replicate the same result as yours. I'm checking this along with the rest of our team to better understand if the limitation comes from the I2C script provided in the D/S.
    I'll let you know of any progress as soon as possible.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 80 points

    Hi Ivan, 

    Thank you for your support !!! 

    If any update about this topic, please let me know. Thanks.

  • 0 in reply to Simon Yuh
    TI__Guru* 95175 points

    Hi Simon,

    I was double checking my test setup from yesterday and noticed that I was using the incorrect low-pass filter setting in the AP, I corrected it and got the following results:

    I tried 2 different configurations with the same results, using the script suggested from data sheet and also using the GUI by selecting PWR_MODE3.
    Attached are both scripts. You may try these and check if you can get similar results as I did.

    DS_script.txt 
    w 70 0E C4 #TDM TX vsns transmit enable with slot 4
w 70 0F 40 #TDM TX isns transmit enable with slot 0
### Run the script from Section 10.1
###### Pre-Reset Configuration #########
w 70 00 01 #Page 0x01
w 70 37 3A #Bypass
w 70 00 FD #Page 0xFD
w 70 0D 0D #Access page
w 70 06 C1 #Set Dmin
w 70 00 01 #Page 0x01
w 70 19 E0 #Force modulation
w 70 00 FD #Page 0xFD
w 70 0D 0D #Access page
w 70 06 D5 #Set Dmin
###### Software Reset #########
w 70 00 00 #Page 0x00
w 70 7F 00 #Book 0x00
w 70 01 01 #Software Reset
d 01 #1 ms Delay
###### Post-Reset Configuration #########
w 70 00 01 #Page 0x01
w 70 37 3A #Bypass
w 70 00 FD #Page 0xFD
w 70 0D 0D #Access page
w 70 06 C1 #Set Dmin
w 70 06 D5 #Set Dmin

w 70 00 01 #Page 0x01
w 70 17 C8 #SARBurstMask=0
w 70 19 20 #LSR
w 70 00 04 #Page 0x04
w 70 30 00 00 00 01 #Merge Limiter and Thermal Foldback gains
w 70 00 08 #Page 0x08
w 70 18 00 00 00 00 #0dB volume
w 70 28 40 00 00 00 #Unmute
w 70 00 0A #Page 0x0A
w 70 48 00 00 00 00 #0dB volume
w 70 58 40 00 00 00 #Unmute
w 70 00 00 #Page 0x00
w 70 03 68 #PVDDL only mode
w 70 73 E0 #DEM dither disabled
w 70 02 00 #play audio, power up with playback, IV enabled

    GUI_script.txt 
    w 70 00 00
w 70 7f 00
w 70 00 00
r 70 02 01
w 70 00 00 
w 70 7f 00 
w 70 00 00 
w 70 02 01 
w 70 00 00
w 70 7f 00
w 70 00 00
r 70 02 01
w 70 00 00 
w 70 7f 00 
w 70 00 00 
w 70 02 02 
w 70 00 00 
w 70 7f 00 
w 70 01 01 
d 01 
i i2cfast 
w 70 00 00 
w 70 7f 00 
w 70 00 01 
w 70 21 00 
w 70 17 c0 
w 70 00 00 
w 70 7f 00 
w 70 00 00 
w 70 02 02 
w 70 08 09 
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w 70 16 40 
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w 70 60 21 
w 70 00 00 
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w 70 10 c4 
w 70 13 08 
w 70 14 0a 
w 70 16 40 
w 70 00 00 
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w 70 02 02 
w 70 03 68 
w 70 04 21 
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w 70 1a 00 
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w 70 1c 36 
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w 70 14 14 00 00 00 
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w 70 18 2b 33 33 33 
w 70 00 00
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w 70 1c 10 00 00 00 
w 70 00 00
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w 70 20 0b 99 99 9a 
w 70 00 00
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w 70 24 0a cc cc cd 
w 70 00 00
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w 70 14 6c cc cc cd 
w 70 00 00
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w 70 4c 39 80 00 00 
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w 70 50 2d 6a 86 6f 
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w 70 54 33 96 51 31 
w 70 00 00
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w 70 58 33 96 51 31 
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w 70 5c 2b d0 52 fc 
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w 70 60 2b d0 52 fc 
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w 70 64 24 0a 54 c7 
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w 70 34 c0 00 00 00 
w 70 00 00
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w 70 38 e0 00 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 3c f0 00 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 40 f8 00 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 44 fc 00 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 48 fe 00 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 4c ff 00 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 50 ff 80 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 54 ff c0 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 58 ff e0 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 5c ff f0 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 60 ff f0 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 64 ff f0 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 68 ff f0 00 00 
w 70 00 00
w 70 7f 00
w 70 00 06
w 70 6c ff f0 00 00 
w 70 00 00 
w 70 7f 00 
w 70 00 00 
w 70 04 21 
w 70 0d 03 
w 70 38 00 
w 70 00 00 
w 70 7f 00 
w 70 00 00 
w 70 5c 19 
w 70 00 00
w 70 7f 00
w 70 00 01
r 70 17 01
w 70 00 00
w 70 7f 00
w 70 00 00
r 70 73 01
w 70 00 00 
w 70 7f 00 
w 70 00 01 
w 70 17 c8 
w 70 00 08 
w 70 18 00 00 00 00 
w 70 28 40 00 00 00 
w 70 00 0a 
w 70 48 00 00 00 00 
w 70 58 40 00 00 00 
w 70 00 00 
w 70 73 e8 
w 70 00 00
w 70 7f 00
w 70 00 00
r 70 02 01
w 70 00 00 
w 70 7f 00 
w 70 00 00 
w 70 02 00 
w 70 00 00
w 70 7f 00
w 70 00 00
r 70 02 01
w 70 00 00
w 70 7f 00
w 70 00 00
r 70 02 01

    Best regards,
    -Ivan Salazar
    Applications Engineer