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LP8758-E3: LP8758-E3 Start-up and part number for order

tony tran
Prodigy 40 points
Part Number: LP8758-E3
Other Parts Discussed in Thread: LP8758-E0, LP8758-EA

Tool/software:

Hello,

I'm looking at the LP8758-E3 to use as a quad output module. I need 1.2V, 1.8V, 2.5V, and 3.3V with Vin at 4V. Max current is approximately 3.2A on one rail, with the others at 2A. Can TI factory program this configuration onto the IC or do I need to program it at start-up? Also, is it possible to run this IC without I2C connected and only use the NRST and enable pins to start the device? I think all variants of this I2C support programming, but I would like to know any specific differences between the -E models other than voltage differences. If TI has a simple model number chart with output voltages, that would be much appreciated. 

I intend to use the eval. board before final implementation, but these are questions I wanted to ask upfront.

Thanks, 

Tony

  • 0
    TI__Genius 9587 points

    Hi Tony, 

    You would need to program the IC at start-up, when nRST is asserted, and before any of the enable pins are set high. 
    We currently do not have any configurations with your desired voltage levels, so these will need to be configured upon startup with I2C. 

    To operate without using I2C, and just the NRST / Enable pins, the default values would have to be preprogrammed into the IC at the factory. 
    We are only able to support custom factory configurations for a certain business case. 
    If you believe you have a large enough business case to warrant a custom configuration, then please reach out to your marketing representative. 

    Else, you would have to use I2C to write your desired settings over the existing configuration.

    Here is a brief summary of the different -E device variants and their default settings:

      VOUT SHUTDOWN_DELAY STARTUP_DELAY ILIM
    LP8758-E0 1000 mV 5 ms 0 ms 2.5 A
    2500 mV 5 ms 0 ms 4.5 A
    1200 mV 0 ms 5 ms 3.5 A
    1800 mV 5 ms 0 ms 4.5 A
    LP8758-E3 900 mV 0 ms 2 ms 4.5 A
    1200 mV 0 ms 3 ms 3.0 A
    1800 mV 0 ms 3 ms 3.0 A
    2700 mV 0 ms 4 ms 4.0 A
    LP8758-EA 800 mV 0 ms 0 ms 4.5 A
    800 mV 0 ms 0 ms 4.5 A
    800 mV 0 ms 0 ms 4.5 A
    800 mV 0 ms 0 ms 4.5 A

    See the respective datasheets for more information on the specific settings like slew rate, mode, EN pin assignment, and masking.

    Best Regards, 
    Sarah

  • 0 in reply to Sarah Lao
    Prodigy 40 points

    Hi Sarah,

    Understood and thank you for the information. I think our business case wouldn't be large enough to support a custom TI configuration. One last question, is there a ILIM setting based on the output voltage. For example, the 1.2V/1.8V rail cannot run at 4a or 4.5A for PN LP8758-E3 in your table. I assume this is just a default setting since the datasheet shows otherwise. Is it also related to thermal limits?

    Best Regards,

    Tony  

  • 0 in reply to tony tran
    TI__Genius 9587 points

    Hi Tony, 

    Correct, the ILIM values I listed above are the default programmed values, but these can be reconfigured via I2C upon startup, before enable. 
    The programmable value can be set higher,  but the total current for all four bucks must not exceed 16 A.

    Same with the voltage levels, these can be reconfigured with I2C upon startup once nRST is asserted high

    This will follow similar steps to the LP8756x family: https://www.ti.com/lit/pdf/SNVU590

    When nRST is high, before any EN pins are high, changes can be made to the setting registers over I2C.

    Let me know if there's any questions or help needed with this process.

    Best Regards, 
    Sarah