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MSP430F5504 USB and Battery Charger

Other Parts Discussed in Thread: MSP430F2274, MSP430F5504, BQ24072

Hi,

I currently have a rechargeable battery application using the msp430f2274 and the BQ24072 power path management. I need to move to the msp430f5504 for future firmware upgrades. What I am trying to figure out is how to manage the Vbus. The charging circuit through the BQ24072 and voltage regulator limits the voltage to 3.3V, which then runs to the current system(msp430f2274). It appears that the msp430f5504 USB Vbus requires at minimum 3.76V for proper operation. Is it possible to use the USB functionality for firmware updates at 3.3V?

Thank you,

  • cody lohse said:
    Is it possible to use the USB functionality for firmware updates at 3.3V?

    How and why? If the device is connected to a PC (which it needs to be able to receive new firmware) then there is 5V VBUS available. And the PC will require 5V signal levels for communication. 3.76V is already a very tolerant low limit.

    The 5504 cannot act as USB host, so if you were thinking of accessing an USB device by the MSP, it won't work.

  • Currently my setup is using the USB only for charging the battery, I need to be able to update the MSP430 firmware, so I need the USB for charging and updating. I currently use the BQ24072 which uses the 5V Vbus as input from the PC and charges the battery, the BQ24072 regulates the output voltage to ~3.4V which then goes out to the MSP430. I was asking if I could use this current setup at 3.3V and still have the functionality to update the MSP430F5504 without having 5V present for the USB on the MSP side. 

    Basically I am trying to avoid adding additional wires (one to power the msp430 Vbus input at 5V and one to power the rest of the system at 3.3V). I have very very limited space.

    I believe what I can do is change the power path management chip to another with a higher Vout and regulate that down to 3.3V later down the line.

  • Hi,

    You can save space using the USB-LDO to power your system and at the same time charge the battery.

    Best Regards,

    AES

  • cody lohse said:
    I was asking if I could use this current setup at 3.3V and still have the functionality to update the MSP430F5504 without having 5V present for the USB on the MSP side. 

    The USB part of the MSP will require 5V Vbus to work. Independently of the rest of the MSP. And if 5V Vbus are present, the internal LDO can be used for generating the 3.3V required for the MSP. However, charging a battery by the LDO is likely not an option due to current limitations.

    So 5V are required for the BQ and for the USB part of the MSP, 3.3V for the CPU part of the MSP, coming either from the MSPs internal Vusb->3.3V LDO, or (in your setup the more likely option) form the BQ/the battery.

    Th eonly thing that's important is that if Vusb is applied to the USB part, the MSP also needs its 3.3V (no matter where they come from)