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TLVM23625: Tlvm23625

Noam Tal
Prodigy 30 points
Part Number: TLVM23625

Hello,

I want to use tlvm23625 in my design.

In my design I have voltage selector (ltc4359).

If I have 5V in the first input of the voltage selector and 0v in the second input I will get 5v in its output.

If I have 5V in the first input of the voltage selector and 19v in the second input I will get 19v in its output.

So when I have 19v I want to use tlvm23625 to get 5v.

The question is when i do not have 19v and have only 5v in the tlvm32625 input, and the FB is designed to output 5v, does this buck will output the input voltage?

Assuming tlvm23625 will pass the 5v input to the output, when i will switch to 19V it will output the 5v without the soft start?

Thabnk you. 

  • 0
    TI__Mastermind 23795 points

    Hi Noam,

    Yes. tlvm23625 will output as close to 5V as possible when VIN is 5V. This is what we refer to as Drop out mode.

    When VIN = 19V, then it should pass 5V to the output. VOUT is only a function of Rfbt and Rfbb. It does not depend on VIN.

    Thanks,

    Andrew

  • 0
    Prodigy 30 points

    Thank you for your assistance,

    I missed that one.

    However I cant find the typical value of VDROP in the datasheet.

  • 0 in reply to Noam Tal
    TI__Mastermind 23795 points

    Hi Noam,

    We are looking into this. I'm ordering an EVM, and it should arrive next week. I appreciate your patience. 

    Thanks,
    Andrew

  • 0
    TI__Prodigy 490 points

    Hi Noam,

    Thank you for your patience. We tested this on the EVM and it appears that for a desired output voltage of 5V, an input voltage greater than 5V is required. When applying 5V to the input of TLVM23625 in this configuration, the device is not able to regulate and Vout remains at 0V. 

    For your application, we would suggest using a different device. Let us know if you have any additional questions or would like assistance in choosing a different part. 

    Regards,
    Carol 

  • 0 in reply to Carol Zhang
    TI__Prodigy 490 points

    Hi Noam,

    We revisited this and found that the reason the TLVM23625EVM required an input voltage greater than 5V to operate at 5V out was due to a resistor divider network on the EVM. When R4 is populated (which it is by default), the input voltage required to set enable high is 7.7V. Schematic is shown below:

    In order to enable the part with an input voltage lower than 7.7V, R4 must either be modified or removed. We removed R4 and found that with an input of 5V, the TLVM23625 is able to output 5V when the device is not loaded. However, the device is unable to maintain 5V out when it is loaded, as the input voltage is too low to maintain regulation. See section 8.4.3.5 Dropout in the datasheet for further explanation. At full load (2.5A), the device operates at 3.8V out (but this drops over time due to device heating. To maintain the 3.8V, a heatsink is required). This was consistent across the switching frequency options available on the EVM. 

    If your TLVM23625 is loaded and 5Vout is required, we would still recommend using a different device. 

    Regards,
    Carol