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TPS544C20: VREF_TRIM setting

Katsu Matsunaga
Expert 7730 points
Part Number: TPS544C20

Hello,

My customer would like to use the trim of output voltage with VREF_TRIM setting.

Please let me know how to set and effect the VREF_TRIM.

For example: make offset as -46mV. VREF_TRIM value should be -23

In this case, what is value in hex/bin set to VREF_TRIM?

Below programming procedure is correct?

1. write trim value into VREF_TRIM

2. write 0x17 to VOUT_MODE

Best regards,

Katsu

  • 0
    TI__Guru 56825 points

     

    VOUT_MODE is read-only and fixed at 0x17, so there is no need to write to it, you would only need to write to VREF_TRIM.

    VREF_TRIM - (Command Code D4h) uses the Write Word (16-bit) format with 2s compliment formatting to represent numbers from -60 to +30 (0xFFC4 - 0x001E) with a 2mV LSB to adjust the reference voltage. 

    To reduce the reference voltage by 46mV from 600mV to 554mV, you would write a value of -23 (FFE9h) to command code D4.

    Because the SMBus transaction byte order for a Write Word places the low-byte first, followed by the high-byte, the byte order would be:

    Start - 7-bit Slave Address + Wr / A / Command Code = 0xD4 / A / Low-byte = 0xE9 / A / High-byte 0xFF / A /  - Stop

  • 0 in reply to Peter James Miller
    TI__Expert 7730 points

    Hi Peter-san,

    Thank you for your support.

    My customer got correct operation with VREF_TRIM.

    About datasheet description of the VREF_TRIM, some bits are read-only. I think it make some conflict for user.

    Best regards,

    Katsu

  • 0 in reply to Katsu Matsunaga
    TI__Guru 56825 points

     

    Sorry about the confusion

    Yes, Bits [14:6] are listed as "Read Only" because the IC ignores them during a write, as they must match Bit 15.

    For negative values, Bits [15:6] equal 1 and bits [5:0] carry the value.

    For positive values, Bits [15:6] equal 0, and bits [5:0] care the value