Output Power of LTM2884CY#PBF

Hello,

   Unfortunately, I'm not aware of a single part/module solution which will provide isolated USB with 500mA @ 5V output when supplied from 5V input.  The LTM2884 can generate your desired output, but only with a higher input supply voltage.  Therefore, I see two possible solutions for your use case:

  1. What you are presently doing which is to use an external supply to either support or replace entirely the isolated supply of the LTM2884.  If the external supply is sized to provide the entire isolated load, then perhaps instead of using the LTM2884 you might consider the ADuM3160 which will provide similar USB isolation performance, but without the duplicate power supply.  Unfortunately, this does result in two items spanning the isolation barrier and doesn't meet your goal of a single module.

2. Another option would be to add a boost power supply to generate a higher input supply voltage for the LTM2884 which would then allow it to provide the desired output power.  There are a number of different boost converters listed here which you might consider: 5V to 12V Boost Converters.  This solution still has an extra supply, but since its not crossing the isolation barrier, you have more flexibility for its placement on the board and it may also be lower cost than the isolated supply of option 1 above. See this link for additional information about the 5V to 12V Boost Converters: https://www.analog.com/en/parametricsearch/11389#/p5362=Boost|Buck-Boost&p5573=min|4.5&p5574=5.5|max&p5357=12|max&p5358=1.77|3.54&p5349=0.4|4&qsfv=vinmin|4.5_vinmax|5.5_vout|12_iout|400m_button|_vout2|_iout2|_vout3|_iout3| 

Eric

Hello,

   Unfortunately, I'm not aware of a single part/module solution which will provide isolated USB with 500mA @ 5V output when supplied from 5V input.  The LTM2884 can generate your desired output, but only with a higher input supply voltage.  Therefore, I see two possible solutions for your use case:

  1. What you are presently doing which is to use an external supply to either support or replace entirely the isolated supply of the LTM2884.  If the external supply is sized to provide the entire isolated load, then perhaps instead of using the LTM2884 you might consider the ADuM3160 which will provide similar USB isolation performance, but without the duplicate power supply.  Unfortunately, this does result in two items spanning the isolation barrier and doesn't meet your goal of a single module.

2. Another option would be to add a boost power supply to generate a higher input supply voltage for the LTM2884 which would then allow it to provide the desired output power.  There are a number of different boost converters listed here which you might consider: 5V to 12V Boost Converters.  This solution still has an extra supply, but since its not crossing the isolation barrier, you have more flexibility for its placement on the board and it may also be lower cost than the isolated supply of option 1 above. See this link for additional information about the 5V to 12V Boost Converters: https://www.analog.com/en/parametricsearch/11389#/p5362=Boost|Buck-Boost&p5573=min|4.5&p5574=5.5|max&p5357=12|max&p5358=1.77|3.54&p5349=0.4|4&qsfv=vinmin|4.5_vinmax|5.5_vout|12_iout|400m_button|_vout2|_iout2|_vout3|_iout3| 

Eric

Thank you Eric for the solution idea and quick response.