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LM51772: Register setting

Roy Chou1
Genius 16055 points
Part Number: LM51772
Other Parts Discussed in Thread: LM251772

Tool/software:

Hi Team,

We would like to LM51772 via I2C setting. Currently, we used EVM to record the register value that we need. And my question is that how can we issue the setting before output voltage enable?

Do you have the recommended flow?

For example, 

1. Power on the LM51772(Vout = 0)

2. Issue the register setting(Set Vout = 20 and current limit = 5A)

3. Enable the Vout

Regards,

Roy

  • 0
    TI__Guru 58521 points

    HI Roy,

    if you hold EN/UVLO low during power on, you can set the register first and then release EN/UVLO to start operation.

    You can also check the LM251772 this will only start after enable is set via I2C  but it has a limited voltage range compared to the LM51772.

    Best regards,

     Stefan

  • 0 in reply to Stefan Schauer
    TI__Genius 16055 points

    Hi Stefan,

    Do you mean that register R/W is working when Vin has power? And we can set EN as low to set initial register setting, after issuing the initial setting, we can set EN as high to have output voltage. Is it correct?

    In addition, we monitor the I2C bus when we power on the LM51772EVM and use GUI. We see that we did some R/W cmd on 0xD4 and 0xD5. May you help comment the procedure meaning?

    Power on.csv

    Regards,

    Roy

  • 0 in reply to Roy Chou1
    TI__Guru 58521 points

    Hi Roy,

    you can access I2C if the device is powered VIN or BIAS, nRST is pulled high and VCC2 has powered up.

    So if EN/UVO is low you can access I2C (and the control registers) while the device is not enabled for DCDC operation.

    Please use the register deception in the datasheet get info on the registers and control bits.

    If something is not clear please highlight the section or ask dedicated question.

    Best regards,

     Stefan

  • 0 in reply to Stefan Schauer
    TI__Genius 16055 points

    Hi Stefan,

    I review the action from GUI and come out the setting for 20V/5A. Below is my setup. For 0xD3/0xD9, may you comment the cmd in detailed? Actually I am not sure why GUI set the kind of setting.

    Give Vin and EN set Lo
    Write below data
    Address Data
    0xD3 0x00 VDET_EN = 0
    0xD9 0x20 Select the lower voltage window threshold refered to VOUT for the PCM
    0x0D 0x03 20V
    0x0C 0xE8
    0x0A 0x64 5A
    EN set Hi

    Regards,

    Roy

  • 0 in reply to Roy Chou1
    TI__Guru 58521 points

    Hi Roy,

    really apologize but I have absolutely no idea what information or comment you would like to get.

    I may just miss understand something and think the wrong way but my understanding is that you ask comment to the different commands but you have already added this in the last column.

    Best regards,

     Stefan