• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 189 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM51770: Start into prebiased output

Nicolas Murguizur
Prodigy 210 points
Part Number: LM51770

Tool/software:

Hi,

While the datasheet indicates the device can be used for charging batteries, I haven't seen any mention into start into a prebiased output like it will be the case with a battery. Is there anything to consider or include in the circuit in that case?

Regards

  • 0
    TI__Guru 65170 points

    Hello Nicolas,

    The LM51770 starts in PSM to avoid current going back to the input during startup. If you want to be 100% sure to have no current flowing backwards during startup, I recommend keeping MODE pin low until the softstart voltage is above the reference voltage.

    For details on the application, please have a look at this app note: https://www.ti.com/lit/an/snvaa80/snvaa80.pdf

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 210 points

    Hi Brigitte,

    Thanks for the reference I read it carefully. In it, having the battery in the 'input port' is proposed. My schematic capture was already completed before reading this document, and I have placed the battery in the 'output port'. I don't require bidirectional operation, as the load is directly connected to the battery.

    I think your recommendation of having the converter in PSM still applies as the converter will work only in forward mode which should address my initial concern of having a very low output voltage reference due to soft start, which due to the high output voltage caused by the battery would require a large current from battery to converter input in order to get to the low output voltage reference. As per my understanding, this should be handled by having the PSM mode. 

    Is there anything else I should take care of? Is there any reason for me to use the architecture in the proposed document where the battery is in the input instead of the output port?

    Regards

  • +1 in reply to Nicolas Murguizur
    TI__Guru 65170 points

    Hello Nicolas,

    Sorry for the late response. You can have the battery attached to the output as well. The only point I have in mind is to have the part during startup in PSM. If you never want the battery to deliver energy to the input, you can even leave it in this mode. Everything else should be described in the datasheet, I think.

    Best regards,
    Brigitte