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LM5157-Q1: Maximum voltage in/out

Part Number: LM5157-Q1
Other Parts Discussed in Thread: LM5158-Q1, LM5156-Q1, LM5157, LM5158, LM5156, LM5156EVM-BST, LM5158EVM-BST

Hi Team,

Our customer is considering using LM5157-Q1 in his project and would like to use an EVM to evaluate the device. However, the 3 available EVM only allows Vout up to 12V~20V. 

The customer has a solar cell having 42V input with 0.4A current output. and would like to know if the evaluation board for this particular IC can take this input and produce more than 40V.

Is there a workaround to do this? or can you give any alternate IC with available EVM that can accommodate?

Thanks in advance.

Regards,

Marvin

  • Hello Marvin, 

    Thanks for reaching out. What topology does the customer want to use (boost, SEPIC, Flyback)? The switch node rating for this device is 50 V abs max and should not be violated. In this case the LM5158-Q1 might be a better fit as the switch node rating is 85 V (https://www.ti.com/product/LM5158-Q1 ). Another option would be the LM5156-Q1 which has an external MOSFET and therefore the customer has the possibility to have a higher voltage on the SW node. Let me know if you need further support. 

    Kind regards,
    EM 

  • Hi EM,

    Thanks for helping. 

    The customer is looking for an EVM which can take 35V - 50V and 0.4 A supply input from a solar cell and can result in 40V to 54V with current output up to 0.4A. I think LM5157 boost converter evaluation module will be suitable for the use case of thew customer.

    Do you agree? can you suggest otherwise?

    Regards,

    Marvin

  • Hello Marvin, 

    Thank you for your message. I would not recommend the LM5157 because for this device the highest recommended value for the input voltage is 45 V and the maximum output voltage is 48 V (page 6 7.3 Recommended Operating Conditions). In this case I would recommend the LM5158 (integrated switch) or the LM5156 (external switch). 

    Kind regards,
    EM 

  • Hi EM,

    Thank you for the response. However, upon checking, the LM5158 (integrated switch) or the LM5156 (external switch) EVM only allow 3-9v/12v. This is beyond what the customer is looking for in an EVM.

    Does this mean that the way these EVMs were designed could not meet the customer requirements?

    Kind regards,

    Marvin

  • Hi Marvin, 

    Let me clarify my previous message. The LM5157-Q1 Boost EVM has the same configuration as the other two mentioned by you (Input voltage range: 3 V to 9 V) and in addition the IC itself has a lower voltage rating. To use the LM5158EVM-BST or the LM5156EVM-BST the customer needs to modify the PCB accordingly, but the IC are the right fit for this application. Let me know if you need further help. 

    Kind regards,
    EM 

  • Hi EM,

    Thank you for your clarification. In regard to PCB modification, can you guide us on how/what to modify to values to make it suitable to match the required input specification?

    Again, thanks for the help.

    Regards,

    Marvin

  • Hello Marvin,

    Let me step in for the moment.

    For changing the input voltage, you need to update the voltage rating on any external components connected to the input voltage.

    For changing the output voltage, you need to update the voltage rating on any external components connected to the output voltage.

    For calculating the external components necessary I recommend using the Excel calculator for the selected device. It can be found in the product folder.

    Best regards,
    Brigitte