• State Resolved
  • Locked Locked
  • Replies 9 replies
  • Subscribers 63 subscribers
  • Views 181 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

LP2954A: Output Isolation

Ascheri Guillaume
Prodigy 10 points
Part Number: LP2954A
Other Parts Discussed in Thread: LP2954, TPS7B86-Q1, LM5069

Dear Power Management Team,

I have some questions about the output Isolation feature et some charateristics of the LP2954 : 

- Is the output stage a bipolar transistor as shown in the block diagram of the datasheet ?

- What is the value of the Reverse Output Current ? (e.g. with the input grounded and the output set at a specific voltage)

- What is the maximum voltage that could be applied at the ouput when the input is grounded ? Absolute maximum rating of the Output pin voltage does not appear in the datasheet.

- Is there a reverse current protection when the ouput is connected to an active voltage source and when the input is set to a specific inferior voltage ? e.g. active voltage source at output=20V and input=15V.

For information, I plan to use two LP2954AIM (adjustable) with their outputs tied together to act as an ‘OR’ function.

BR,
Guillaume

  • +1
    TI__Mastermind 23361 points

    Hi Guillaume, 

    Is the output stage a bipolar transistor as shown in the block diagram of the datasheet ?

    -- Yes. 

    - What is the value of the Reverse Output Current ? (e.g. with the input grounded and the output set at a specific voltage)

    -- The reverse current at this situation is not controlled, and the LDO will need to be protected using external diode. 

    - What is the maximum voltage that could be applied at the ouput when the input is grounded ? Absolute maximum rating of the Output pin voltage does not appear in the datasheet.

    --Reverse battery protection is provided for the IN pin as shown in the absolute maximum voltage table. 

    - Is there a reverse current protection when the ouput is connected to an active voltage source and when the input is set to a specific inferior voltage ? e.g. active voltage source at output=20V and input=15V.

    -You will need to implement external protection for reverse current. 

    Regards, 
    Jason Song

  • 0 in reply to Jason Song
    Prodigy 10 points

    Hi Jason,

    Thank you very much for your quick and complete answer.

    I have one last question : does TI have a LDO regulator that includes a reverse current protection that could fit my application ?

    Regards,

    Guillaume

  • +1 in reply to Ascheri Guillaume
    TI__Mastermind 23361 points

    Hi Guillaume, 

    We do have LDO that has reverse current protection built-in, but most of them are targetting for automotive appliations. To get you the best part, will you help to reconfirm your Vin, Vout and load current in the application? 

    Regards, 
    Jason Song

  • 0 in reply to Jason Song
    Prodigy 10 points

    HI Jason,

    Again, thank you for your answer. 

    Here are the parameters : Vin = 19V to 21V, Vout = close as possible to Vin (drop-out voltage is crucial), Iout = 200mA max.

    (Availability, lead time and life cycle  are also critical).

    BR,

    Guillaume

  • +1 in reply to Ascheri Guillaume
    TI__Mastermind 23361 points

    Hi Guillaume, 

    There is a global IC shortage, and to help with lead time, would you let us know your targetted production time and volume? Any preferences on the package size? 

    Regards, 
    Jason Song

  • 0 in reply to Jason Song
    Prodigy 10 points

    Hi Jason,

    Thank you for your reply.

    QFN package are not allowed in our designs. Production time for the first batch is 30 weeks and total estimated volume is 40 000 over 15 years.

    BR,

    Guillaume

  • 0 in reply to Ascheri Guillaume
    TI__Mastermind 23361 points

    Please allow 1 day for us to investigate for you. Will update here soon.

  • +1 in reply to Jason Song
    TI__Mastermind 23361 points

    Please take a look at TPS7B86-Q1 and this is probably the best option for now that will meet your needs. 

  • 0 in reply to Jason Song
    Prodigy 10 points

    Hi Jason,

    Thank you again for your reply.

    Unfortunatly, Vout max=18V which is far from the P20V input. Here is a  clarification about Vout : Vout=18.5V min and 20.5V max.

    Finally, a LDO is not needed anymore as a design with a LM5069 current limiter and a some of diodes will perform this 'OR' function.

    Thank you again for your help on this topic,

    BR,

    Guillaume