• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 238 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

LM61460: Datasheet Section 9.2.4 - Achieving 20V output from a 20V input

Obinna Ezeilo
Intellectual 2385 points
Part Number: LM61460

Hi team, 

For a USB PD application my customer  is trying to get a 20V output from a 20V input with the LM61460. In section 9.2.4 of the datasheet , figure 94 shows an exact typical application achieving such.

However there is no detailed design procedure attached to the circuit. The detailed design procedure link in section 9.2.4.2 applies to figure 30 ( 13.5Vin & 5Vout). 

Hence my questions: 

1. Can the requirement of 20Vin to 20Vout be achieved with this IC? 

2. Is there a detailed design procedure for the typical application in figure 94? Can you please share? 

Thanks, 

Obinna. 

  • 0
    TI__Guru 50120 points

    Hi Obinna,

    1. I don't think you can operate this part at 100% duty cycle. This will result in dropout condition where the output will trail the input by a diode drop. Also WEBENCH doesn't allow this power conversion. It is possible to do a 24Vin|20Vout|5A power conversion if the customer wanted.

    2. Let me contact the previous apps engineer who wrote the datasheet and get back to you on how this was typical application circuit was created. In the mean time if you weren't aware, there is an online calculator tool "LM61460 Design Tool" in the (Design & development) tab of the product folder. This should help customers get started on picking the appropriate BOM components. As for PCB layout, it is recommended to follow Section 11.1 Layout guidelines in the datasheet.

    Regards,

    Jimmy  

  • 0 in reply to Jimmy Hua
    TI__Guru 50120 points

    Update- I was able to get ahold of the previous apps engineer.

    For USB Type C application with dynamically adjusted output voltage, the top and bottom resistor should be picked such that the small signal loop response results (crossover frequency and phase margin) are good. The design calculator tool should help provide some guidance with the bode plot simulation results.

    The voltage injection resistor is picked such that current can only be sinked into the FB and not sourced out of it. 

    Figure 94 schematic has been tested to work and should be the recommended BOM selection for customers that want to implement the LM61460 circuit for USB Type-C power supply applications. 

  • 0 in reply to Jimmy Hua
    TI__Intellectual 2385 points

    Hi Jimmy, 

    If this part can't operate at a 100% duty cycle (as you mentioned previously), how will figure 94 schematic work? 

    Thanks. 

    Obinna. 

  • 0 in reply to Obinna Ezeilo
    TI__Guru 50120 points

    Hi Obinna,

    Thanks for pointing that out. I was still ramping up on this device and had to talk to the previous apps engineer on this to understand TypeC application and so I would like to retract that point 1 statement.

    Figure 94 should be applicable for your customer design.

    Regards,

    Jimmy