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TPS7A78: Load greater than 120mA - parallel outputs?

Prodigy 160 points

Replies: 4

Views: 187

Part Number: TPS7A78

Hello,

I need to supply a load with 5V/0.3A. I see in the datasheet that the maximum allowed is 120mA.

  1. Is it allowed to connect 3 units of TPS7A78 in parallel?
  2. Can I share the Cs capacitor with all the units?
  3. Do TI have a smaller solution for this (no need of isolation)?

Thanks

  • Hi Avihai,

    You can parallel 3 of the TPS7A78 to enable current sharing, however you would need to add discrete circuitry in order to balance the load across all three. What type of system would you be powering: Digital, analog signal chain, ADC/DAC?

    If you need smaller size and can work with DC/DC converters you can look at our selection of power designs that can help you get a small size. The TPS7A78 at 120mA will consume a bit of board space vs a flyback or a DC/DC converter.

    Here are some examples:

    http://www.ti.com/reference-designs/index.html#search?iout=0.3,1&vout=5&intype=AC&famid=64 

    Best Regards
    Jose G. Gonzalez Torres | Product Marketing | LDO and Linear Regulators

  • Hi Avihai,

    For your questions 1 & 2, I have to do some bench testing to accurately answer the questions since the answers will be referenced for similar future questions from other customers as well, I will get back to you by Monday June 10th.

    for question number 3, TI has UC288xx converters that can support your application requirements.

    BR,

    Haidar

  • In reply to Haidar Hamoo:

    Hi Avihai,

    As promised in my previous post, so for your #1 question; I have bench tested two parallel TPS7A78 devices to support 240 mA after adding a Ballast resistors before the load to overcome the difference in the output voltages between the two TPS7A78 devices as Jose mentioned in his post. You can find more information on connecting LDO in parallel in the link below:

    A special consideration for TPS7A78 device is that all the parallel devices must share the same GND ether floating of connected to earth-GND. 

    As for #2, you can connect three TPS7A78 devices that share the same Cs capacitor by connecting Cs to one of the devices while tying SCIN pins and GND pins for the three devices together respectively as shown in the attached plot;

    But keep in mind that Cs need to be sized for your load which will result in very large Cs cap size, i.e. expensive and maybe not available.

    BR,

    Haidar

        

  • Thank you for the answers!

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