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TPS2121: Questions related to datasheet

Ryan Yuen
Intellectual 260 points
Part Number: TPS2121
Other Parts Discussed in Thread: TPS2120

Hello Ti,

I am designing a 2-input power mux circuit. I am studying the datasheet but I am confused on something.

This is the photo I captured from the EVM user manual (Pg. 9 of http://www.ti.com/lit/ug/slvubd2/slvubd2.pdf

  • 0
    Intellectual 260 points

    (Sorry some content is missing in the previous post)

    This photo is also captured from page 3 of the same datasheet.

    Refer to schematic, for setting PR1 in 12V, user should connect J3. However, why would table 4(second photo) suggest J5 & J6?

    Basically I want to achieve

    Vin1: 12V-DC +/- 2V

    VIn2: 12V-Bat +/- 2V

    Iout: 2A

    Is it possible to achieve that by using TPS2121? If possible, how to properly design the resistor divider in automatic switchover (without external VREF)? 

    Thanks

    Ryan

  • 0 in reply to Ryan Yuen
    Intellectual 260 points

    Hello 

    Is this possible to satisfy my requirement?

    Thanks 

    Ryan

  • 0 in reply to Ryan Yuen
    TI__Genius 10855 points

    Hi Ryan, 

    Thanks for reaching out on E2E!

    Good catch on the typo in Table 4, it should say "J1 sets 3.3V, J2 sets 5V, and J3 sets 12V". We are currently updating the EVM User's Guide so I will make this additional change as well.

    Switching between two 12V inputs @ 2A seems like a good fit for the TPS2121. If you look at the Applications Section of the TPS2121 datasheet, there's a few common configurations and steps on how to configure the device for each configuration. 

    Looking at your schematic, I don't see anything wrong with the configuration. The device will switch from IN1 to IN2 when IN1 drops below ~9.84V. If you want to add adjustable hysteresis, you can tie a resistor from the ST pin to PR1, similar to the configuration shown on page 27 of the datasheet.

    Let me know if you have any additional questions.

    Thanks,

    Arthur Huang

  • 0 in reply to Alpha H
    Intellectual 260 points

    Hello Arthur,

    Thanks for your reply. I have one more question.

    Is there any documentation shows the recommended land pattern for TPS2121 (VQFN)? I noticed only TPS2120 (YFP) is listed in the datasheet. 

    Thanks

    Ryan

  • 0 in reply to Ryan Yuen
    TI__Genius 10855 points

    Hi Ryan, 

    Please find the landing pattern for the TPS2121 attached. We are currently updating the TPS2121 datasheet, the next revision should have the landing pattern attached in the datasheet. 

    For reference, could you provide more details on your application? mpqf508.pdf

    Thanks,

    Arthur Huang

  • 0 in reply to Alpha H
    Intellectual 260 points

    Hello Arthur, 

    Thanks for the file. 

    I am designing a backup power system with 12V-DC and 12V-battery as a power source. In the normal operation, the system will draw power from 12V-DC. When the DC power is not available, it will automatically switch to 12V-battery. 

    Ryan