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TAS2557EVM: Boost Mode Control on RomMode2

SeungKyu Joo
Prodigy 60 points
Part Number: TAS2557EVM
Other Parts Discussed in Thread: TAS2557, TAS2563, TAS2562

Dear Expert,

I have some question of Boost Mode on Rom Mode2.

In the datesheet, boost mode is automatically enabled by the TAS2557 internal algorithm.

9.3.11.1 Boost Mode
The TAS2557 internal processing algorithm automatically enables the boost when needed. A look-ahead
algorithm monitors the battery voltage and the digital audio stream. When the speaker output approaches the
battery voltage the boost is enabled in-time to supply the required speaker output voltage. When the boost is no
longer required it is disabled and bypassed to maximize efficiency. The boost can be configured in one of two
modes. The first is low in-rush (Class-G) supporting only boost on-off and has the lowest in-rush current. The
second is high-efficiency (Class-H) where the boost voltage level is adjusted to a value just above what is
needed. This mode is more efficient but has a higher in-rush current to quickly transition the levels. This can be
configured using Table 8.

1. How can we check whether boost mode is enabled or not?

2. Is boost mode automatically enabled on Rom Mode1 and Rom Mode2?

3. Is there a way to check boost mode enable by the register?

4. Is there a way to control boost mode enable by the register?

Thanks,

SeungKyu Joo

  • +1
    TI__Guru** 102155 points

    Hi SeungKyu,

    1. How can we check whether boost mode is enabled or not?
      1. You may read Book 0 Page 0 Register 0x64
        1. Bit 5 toggles depending on the Boost state, which depends on Book 0 Page 0 Register 0x02 Bit 5
        2. Bit 4 toggles depending on the pass-through action. Pass-through means PVDD/VBST is the same level as VBAT, this happens when input signal is low such that higher voltage is not required.
    2. Is boost mode automatically enabled on Rom Mode1 and Rom Mode2?
      1. As you may notice on Book 0 Page 0 Register 0x05, the boost is disabled by default (as many other features). This has to be enabled as part of the initialization script. Also by default the boost, if enabled, operates in Class-H mode.
    3. Is there a way to check boost mode enable by the register?
      1. If you refer to whether the boost is operating or not, regardless of the boost enable control, you may inspect Book 0 Page 0 Register 0x64 Bit 4
    4. Is there a way to control boost mode enable by the register?
      1. If you refer to force the boost to be always on or always off, that option is not available on this device

    As follow up questions:

    • Can I ask how you selected TAS2557 for your application? What features, power range, voltage rails are you looking for?
    • Perhaps you can consider some newer devices like TAS2562 and TAS2563

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 60 points

    Hi Ivan Salazar,

    Thank you for your support.

    We just want to measure how Boost Voltage (VBST) is changed in Class-H Mode.

    Before measure it, I just want to check some information about Boost Mode control.

    I'll open new question if we need more.

    Thanks,

    SeungKyu Joo

  • 0 in reply to Ivan Salazar
    Prodigy 60 points

    Hi Ivan Salazar,

    I'm Sorry but one more question.

    I set Class-G Mode and when I checked VBST is changed about 8V on Rom Mode2.

    But when I check "Book 0 Page 0 Register 0x02", the value is 0x00.

    Does it means that the boost is disabled?

    But I want to know why VBST is changed.

    Thanks,

    SeungKyu Joo

    =====================================================
    <Direct I2C Control for Class-G Setting>
    # w 98 00 00
    # w 98 7f 00
    # r 98 09 01

    <Direct I2C Control for Read Register>
    - I2C Control
    w 98 00 00
    w 98 7f 00
    r 98 64 01

    w 98 00 00
    w 98 7f 00
    r 98 02 01

    - Output
    # Write command at line 21
    Successfully written
    # Write command at line 22
    Successfully written
    # Read command at line 23 : r 98 64 01
    fc
    # Write command at line 30
    Successfully written
    # Write command at line 31
    Successfully written
    # Read command at line 32 : r 98 02 01
    00
    =====================================================

  • +1 in reply to SeungKyu Joo
    TI__Guru** 102155 points

    Hi SeungKyu,

    Sorry I did a mistake in my last post. Register 0x02 from Book 0 Page 0 is not used, actually it is not listed in the data sheet register map.
    It is Book 0 Page 0 Register 0x05 instead. I'm making some changes on my last post to show the correct information:

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 60 points

    Hi Ivan,

    I'm sorry but I have more question.

    As I commented, I measured VBST on Rom Mode2.

    I use "1Khz Fade In (-Infinite to 0 db) " Content to check boost voltage level change on Class-H like below.

    But VBST is directly changed from about 5V to about 8.5V even though Boost Mode is set Class-H or Class-G both case.

    Below is the register control for setting Class-H.

    # BOOST_CTRL_1
    # [0] BST_Mode
    # Class-H operation using Multi-level (0)
    # Class-G operation using one level turned on and off as needed (1)
    w 98 00 00
    w 98 7f 00
    w 98 09 24
    r 98 09 01

    Are there anything more?

    Thanks,

    SeungKyu Joo

  • 0 in reply to SeungKyu Joo
    TI__Mastermind 33285 points

    Hi SeungKyu,

    Today is a TI Holiday and our experts are out of office. Please give us another day to look at and answer your question. For record keeping purposes please do not reply to this message unless 48 hours have passed without a response.

    Thank you for your patience,

    Jeff

  • 0 in reply to SeungKyu Joo
    TI__Guru** 102155 points

    Hi SeungKyu,

    Class-G is enabled by default after POR. PPC3 is not modifying this register value.
    Boost is controlled by register 0x09 from book 0 page 0, its default value is 0x25.
    In order to enable Class-H you would need to write 0x00 to this register, you should be able to notice a longer ramp when boost is going up, although headroom is most likely powering up the boost all the way to the max value. Please notice that boost controller on TAS2557 is a previous version of TAS2563 which has better envelope tracking.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Prodigy 60 points

    Hi Ivan,

    Thank you for your update.

    By the way, VBST is stiil directly going up from about 5V to about 8.5V even I change 0x00 value by  register 0x09 from book 0 page using Direct I2C on PPC3.

    w 98 00 00
    w 98 7f 00
    w 98 09 00 #Class-H
    r 98 09 01

     

    Test Content is "1Khz Fade In (-infinite to 0db)" during 1 minute.

    I don't know it is normal operation or not.

    Thanks

    SeungKyu Joo

  • 0 in reply to SeungKyu Joo
    TI__Guru** 102155 points

    Hi SeungKyu,

    Based on previous observations, that may be the expected results, you may need to change to a newer device like TAS2563 for a more define Class-H control.

    Best regards,
    -Ivan Salazar
    Applications Engineer