• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 407 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.

TPS73801: Alternate Solution?

Vishal A1
Intellectual 540 points
Part Number: TPS73801
Other Parts Discussed in Thread: LM317

Hi ,

We are using "TPS73801" for battery charging at 11.5V@1A . We assumed that the LDO would limit the charging current beyond 1A  and maintains @1A current. But the LDO is supplying beyond the rated current of 1A.As we checked the datasheet ,the internal current limit is 1.6A. Our requirement is to charge the battery @1A constant current and with this solution we cannot attain it.Please share us a suitable battery charging solution that can charge @1A and the output voltage is adjustable to 11.5V.

Also please let us know if there is any part that is footprint and pin to pin compatible to TPS73801 and has rated current @1.5A or greater.

  • 0
    TI__Guru 50090 points

    Hi Vishal,

    Most LDO's have the current limit set well above the actual recommended limit. There are a couple of reasons for this.

    1. We want to guarantee that we can deliver the rated current. 

    2. The current limit is not extremely precise

    3. The LDO's primary goal is to regulate current. The over current and over temperature limits are there to protect the LDO. 

    One Idea to make an LDO work as a linear charger might be to use the current to lower the LDO's regulation voltage as a function of current. Here is an example of doing that with a DC/DC converter (this one actually raises the voltage to compensate for IR losses in the power path, but should be able to be modified for lowering the LDO's regulation voltage when the current exceeds the desired threshold).

    I hope this helps.

  • 0 in reply to JCHK
    Intellectual 540 points

    Hi John Cummings,

    Thanks for the information.

    Please let us know if there is any part that is footprint and pin to pin compatible to TPS73801 and has rated current @1.5A or greater. Also please suggest any part that closely matches the same.

  • 0 in reply to Vishal A1
    TI__Guru 50090 points

    HI Vishasl,

    Unfortunately, there is no pin to pin. The pinout of the TPS738 is unique and the 6 pin SOT-223 is not a very popular package. 

    One regulator that has been historically popular for this type of application is the LM317. A very simple example is shown below:

    One of the unique features of the LM317 is the implementation of its overload protection. The Darlington output stage self regulates to protect the device. Meaning, If the product (VIN-VOUT)*ILOAD is causing the device to get too hot, it automatically throttles back the load current to keep it working. This should mitigate the issue you are seeing. 

    I hope this helps.