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Original question:

LM5177: C-code driver for I2C

LM51772: Configuration

? ?
Prodigy 10 points
Part Number: LM51772

Tool/software:

Hello TI,

I am using LM51772 with internal FB, want to get a min. output of 1v. Thus I clear SEL_FB_DIV20 in MFR_SPECIFIC_D8 register, but still the min. Vout is 3.3v. any value less than 0x014A witten to VOUT_TARGET1_LSB and VOUT_TARGET1_MSB does not work. 

Is there any other configuration required to switch to DIV10 range to get min. 1v output?

Thanks in advance.

Tony

  • 0
    TI__Mastermind 22215 points

    Hi Tony,

    It is a bank holiday today. Please expect a reply by Tuesday.

    Best Regards,
    Feng

  • 0 in reply to Feng Ji
    TI__Guru 58361 points

    Hi Tony,

    no, there is no other setting for the output voltage beside the SEL_FB_DIV20 and the VOUT_TARGET Registers.

    Note: the min voltage you can adjust with I2C is 1.65V as the settings are internally limited to 3.3V or 1.65V (depending of the setting of SEL_FB_DIV20).

    Best regards,

     Stefan

     

  • 0
    Prodigy 10 points

    Hi Stefan,

    Thanks for your feedback, but that is not what I saw.

    During the init, I cleared teh SEL_FB_DIV20, but still I could not set the VOUT below 3.3v.

    Below is the dumpped register value after init.
    LM51772 ILIM Threshold:64
    LM51772 Vout LSB:4A
    LM51772 Vout MSB:01
    LM51772 USB_PD Status:00, CC_OPR:0
    LM51772 Reg Status:00,ON,UV no fault
    LM51772 USB PD Control0:01, CONV_EN2:1
    LM51772 MFR D0:32, CONV_EN:0
    LM51772 MFR D1:09
    LM51772 MFR D2:46
    LM51772 MFR D3:80, VDET_EN:0
    LM51772 MFR D4:03
    LM51772 MFR D5:3F
    LM51772 MFR D6:95
    LM51772 MFR D7:36
    LM51772 MFR D8:00, DIV20:0
    LM51772 MFR D9:00, ISET:0
    LM51772 IVP VOL:FF

    Afterwards, i start to set VOUT from 1650mv, but the read out value from VOUT is always 0x014A, actual output voltage is also 3.3v, till the set value is greater than 0x014A.

    LM51772 Vout set:1650mV
    LM51772 Vout Write:0x00A5

    LM51772 ILIM Threshold:64
    LM51772 Vout LSB:4A
    LM51772 Vout MSB:01
    LM51772 USB_PD Status:00, CC_OPR:0
    LM51772 Reg Status:00,ON,UV no fault
    LM51772 USB PD Control0:01, CONV_EN2:1
    LM51772 MFR D0:33, CONV_EN:1
    LM51772 MFR D1:09
    LM51772 MFR D2:46
    LM51772 MFR D3:80, VDET_EN:0
    LM51772 MFR D4:03
    LM51772 MFR D5:3F
    LM51772 MFR D6:95
    LM51772 MFR D7:36
    LM51772 MFR D8:00, DIV20:0
    LM51772 MFR D9:00, ISET:0
    LM51772 IVP VOL:FF

    LM51772 Vout set:1660mV
    LM51772 Vout Write:0x00A6

    LM51772 ILIM Threshold:64
    LM51772 Vout LSB:4A
    LM51772 Vout MSB:01
    LM51772 USB_PD Status:00, CC_OPR:0
    LM51772 Reg Status:00,ON,UV no fault
    LM51772 USB PD Control0:01, CONV_EN2:1
    LM51772 MFR D0:33, CONV_EN:1
    LM51772 MFR D1:09
    LM51772 MFR D2:46
    LM51772 MFR D3:80, VDET_EN:0
    LM51772 MFR D4:03
    LM51772 MFR D5:3F
    LM51772 MFR D6:95
    LM51772 MFR D7:36
    LM51772 MFR D8:00, DIV20:0
    LM51772 MFR D9:00, ISET:0
    LM51772 IVP VOL:FF

    And in datasheet, it was mentioned the minimum output could be 1v, in 2nd item of features on page1, also in description to register 0x0C and 0x0D.

    Please help to check.

    Looking forward to your feedback.

    Tony

  • 0 in reply to ? ?
    TI__Guru 58361 points

    Hi Tony,

    sorry, may last reply was not fully accurate.

    With the current version of the GUI you cannot set the output voltage to a value below 3.3V as the GUI is blocking to write lower values.

    Are you using the GUI or an own software to set the values for VOUT?

    Note: when writing VOUT you need to write both registers to get the value accepted by the controller.

    Best regards,

     Stefan

  • 0 in reply to Stefan Schauer
    Expert 2580 points

    Hi Stefan,

    Can the LM51772 achieve an output of 1-30V?

    Are there any particularly suitable products that can be recommended?

    Thanks~

  • 0 in reply to Rhea Gao
    TI__Guru 58361 points

    HI Rhea,

    yes, with the VOUT and SEL_FB_DIV20 the output voltage can be set between 1V and 48V.

    Note: with SEL_FB_DIV20 the output voltage will jump between the two voltage defined by SEL_FB_DIV20 and VOUT register while with VOUT you can change it with 10/20mV steps

    Best regards,

     Stefan

  • 0 in reply to Stefan Schauer
    Expert 2580 points

    Hi Stefan,

    At present, there are still two problems. Please help solve them:

    1. Currently, the lowest output voltage in the 10mV file is 3.3V. The data describes that it can reach 1V. Please help confirm whether it can reach 1V or 1.65V again.

    2. Currently, the constant current mode cannot be entered. How should it be operated? Now the constant current mode needs to be used. It can be set to be lower than 3.3V, but once set, it cannot be changed. As soon as the register output is changed, it becomes 3.3V. The reason is unknown.

    Thanks!

  • 0 in reply to Rhea Gao
    TI__Guru 58361 points

    Hi Rhea,

    1. as already mentioned the current GUI does not support setting the output voltage lower then 3.3 V. If you send the I2C command via another tool you can sent the output voltage with SEL_FB_DIV20 bit set to 0 also down to 1.0V.

    2.Also the current control works on the low input voltage but accuracy gets very low.

    How have you configured your system (R on ISNS and components on ILIM ?

    Best regards,

     Stefan