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TPS2595: Power switches inquiries

Danilo A.
Mastermind 28740 points
Part Number: TPS2595
Other Parts Discussed in Thread: TPS61089, TPS62132, TPS62130, , TPS25947, TPS25940-Q1, TPS22810, TPS1H100-Q1, TPS1HC100-Q1, TPS1HB16-Q1, TPS1HB08-Q1

Hi Team,

We would like to ask your help regarding our customer's inquiry below.

Hello, in our prototype design, we are using your DC/DC converters (TPS62132, TPS62130,TPS61089). Obviously they are isolated from each other since they output different voltages, but they share the same source (which is the battery pack).

I am reading thru your "Basics of Power Switches" application report and I am interested on how to use your power switches to protect the input and output of the DC/DC converters.

For the input side, the report shows using an efuse. Could you please guide me in designing which efuse to use if I will use your 3 converters (they still share the same battery pack)? For example, will the current limit of each 3 efuses be the maximum battery pack current output?

For the output side, your report shows separately using a load switch and a high-side switch. While I understand the benefits of each power switch topology, I am still at a loss at picking the most comprehensive protection for my circuit. I am inclined to use 2 or more power switches together on a single line to get the protection I want. I have 2 combos I thought of:

  1. load switch and efuse, sequentially
  2. efuse and smart high-side switches, vice versa

Are these combos suitable? Were these power switches tested together in this manner by TI in the past? Were they viable for automotive applications?

The protection I am seeking is comprehensively covering all the functions found in Table 1 of the report. The circuit will be flown in a cube satellite therefore "extraordinary" protection is needed for my circuit.

Please advise and thank you for your patience and guidance.

Regards,

Danilo

  • 0
    TI__Guru* 79181 points

    Hi Danilo,

    1. What is battery operating voltage?

    2. How much is max current draw by each dc/dc converter?

    3. What is the load at output of dc-dc converter? 

    4. What is the output voltage of each dc-dc converter?

    If there is some block diagram that will help. 

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    TI__Mastermind 28740 points

    Hi Kunal,

    Our customer shared the schematic diagram and battery specs below. According to him,

    Our battery pack has a minimum voltage of 6V and a maximum voltage of 8.4V. This comes from a 2S2P configuration of a Li battery.

    As for the load, there are a lot of loads connected to different converters so I cannot say that there is only 1 type of load. Regardless, I would need protection for these loads and the converters themselves.

    7026.NCR18650B.pdf

    Regards,

    Danilo

  • 0 in reply to Danilo A.
    TI__Guru* 79181 points

    Hi Danilo,

    Thanks for all info. What I meant is , in steady state how much is max current that each converter would be taking from battery? This way we will decide what should be current limit of efuse and which efuse to use .

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    TI__Mastermind 28740 points

    Hi Kunal,

    According to our customer,

    I'm not sure what is the maximum recommended input current of each converter based from the datasheets. But I guess we can assume a steady state max current is the maximum operable input current for each converter.

    I think this would be reasonable.

    Regards,

    Danilo

  • 0 in reply to Danilo A.
    TI__Guru* 79181 points

    Hi Danilo,

    Let me discuss with team on this. 

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    TI__Guru* 79181 points

    Hi Danilo,

    I will get back with response today. Can you check if they only need automotive grade parts?

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    TI__Mastermind 28740 points

    Hi Kunal,

    The customer application is for cube satellite.

    Regards,

    Danilo

  • 0 in reply to Danilo A.
    TI__Guru* 79181 points

    Hi Danilo,

    On the input side they can use eFuse on each path. On the output side they can use efuse ->load switch or efuse->HSS depending on type of load. For the onboard load like microcontroller they can use load switch and for off the board load such as inductive load , HSS can be used. 

    each eFuse current limit has to be slightly higher than the total max steady state current of load on each converter rail. 

    efuse recommendation: TPS2595,TPS25947,TPS25210

    To learn more about driving load from HSS customer can refer this app note:https://www.ti.com/lit/an/slvae30e/slvae30e.pdf?ts=1640258498529&ref_url=https%253A%252F%252Fwww.google.com%252F

    I understand application is satellite but customer asked in first question were power switches viable in automotive so I thought they are asking parts that are automotive qualified like TPS25940-Q1, so automotive qualified parts are not a necessity ,right? 

    Regards

    Kunal Goel

  • +1 in reply to Kunal Goel
    TI__Mastermind 32650 points

    Hi Danilo,

    In addition to the eFuse recommendations, what are the protection features required on the output side?

    If the protection required is minimal, then a load switch like TPS22810 could work. If more features like ability to drive external inductive loads and current limiting is required, then a high side switch is preferred. For the lower current loads, I would recommend looking at TPS1H100-Q1 and TPS1HC100-Q1.

    For high current loads, devices like TPS1HB08-Q1 and TPS1HB16-Q1 have no problem supporting 7A DC.

    Thanks,

    Shreyas