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TPS61089: PFM Mode and Output Power

Ryan.Bishop
Expert 3900 points
Part Number: TPS61089
Other Parts Discussed in Thread: TPS61088, , TPS61178

Hello,

The customer is looking at TPS61088, TPS61089, and TPS61178 for the boost conversion in their system.

  1. We noticed that all three of those device have an option to enter PFM at light load to maintain efficiency. However, TPS61178 specifically mentions a "Power Save Mode" on page 15. Does that device do any extra to save more power than the other devices, or is Power Save Mode just lingo for PFM mode.

  2. Figure 10 of the TPS61178 datasheet show the switch current limit can be set to 15A. Is it okay to operate the device in that setting?

Here are the input/output conditions. What is the maximum output current we can safely supply? Do you recommend the TPS61178?
  1. Vin is Li-Ion cell, so potentially as low as 3V
  2. Vout is 12V
  3. The customer would like to supply 3A output, but we realize this might not be feasible.


Regards,
Ryan B.

  • 0
    TI__Mastermind 40080 points

    If the output is a continuous current, TPS61178's peak switch current limit can be set at maximum around 8A. For the 12V output, I suggest use TPS61088, which has bigger output current. But TPS61088 can only support 12V/2.2A maximum output current at Vin=3V condition.  Is 3A output a continuous current? If   it is a continuous current, suggest them use controller.

    By the way, could you please share the usage with us? We need to know the marketing requirements. I'll send a message to you.

  • 0 in reply to Helen chen
    TI__Expert 3900 points

    Thank for you the help!

    Any comments on question #1?

    I will recommend the customer focus on the TPS61088 since they will need as much output current as possible. The customer is currently looking to see if they can relax the load requirements to less than 3A. Maybe they can make 2.2A possible. How did you come up with that 2.2A number so I can explain to the customer?

    The problem with the controllers is that any device with Vin down to 3V has very high Iq. Since this is battery operated Iq is very important: www.ti.com/.../products.html

    If we can't make the TPS61088 work, I'm also proposing this design: http://www.ti.com/tool/PMP8921

    The heavy load is somewhat continuous, more than a few seconds but less than a minute.

    Thanks again!

    Ryan B.

  • 0 in reply to Ryan.Bishop
    TI__Mastermind 40080 points
    Yes, for the TPS61178, power save mode means PFM mode at light load. You can use PMP8921 , you can also use controller TPS5122.