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MSP432P401R: USB Powered Design w/ MSP432 using the FT232R chip by FTDI

Shane Yost
Prodigy 90 points

Part Number: MSP432P401R

I'm spinning a board where I'm essentially using a FT232R chip for a back channel uart interface and for powering my board. In the FT232R manual it mentions various concerns with how much current my application will draw. For example, below (see attachment) or page 23 of FT232R datasheet under section "USB Bus Powered Configuration (http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf) is the page describing some of these "Basic rules" as they call them. My questions specifically are...

1) How much current will a MSP432 draw (is it greater than 100mA)?

2) When sourcing power to the MSP432 can I come right off the Vcc connection shown below (also should it be before or after the Ferrite Bead)?

3) Should I use any additional caps on the Vcc line coming into the Vcc pins of the MSP432?

  • 0
    TI__Mastermind 22640 points
    Hello Shane,

    I have forwarded your post to one of my colleagues who has more knowledge about this topic.

    Thanks,
    Sai
  • 0 in reply to Sai Reddy
    TI__Expert 8510 points

    Shane,

     1.The max power will depend on your CPU acitivity and whether you are using the DCDC or LDO regulator (DCDC is less). The MSP432P401R datasheet has the max power drawn by the CPU as 8.4mA using the LDO.  The peripheral draw is relatively smaller (see Table 5.23 Current Consumption of Digital Peripherals for actual values). Collectively you can estimate this as < 2mA .  The (potentially) larger draw is from the IOs, whose power will be a function of frequency x load x  #IOs. (Standard CV^2F power calculation).

     2,3. Tap after the ferrite bead- it's there to filter out noise! See the MSP432P401R LaunchPad User's Guide for a schematic showing how the MSP432 should be connected to it's power grid (including bypass caps)

    -Bob

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