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BQ25713: questions regarding the pmp40441 VBUS input and also bq25710 compatibility

Part Number: BQ25713
Other Parts Discussed in Thread: PMP40441, TUSB422, MSP430BT5190, BQ40Z50, BQ40Z50-R2, MSP430FR5949, TPS2121, BQ25710,

I'm finishing a charger design to complement an already existing system (12V) and am using the pmp40441 as the main reference for this design. I need to know if this design is only compatible with usb-pd input or if i can run a dc barrel jack input (12V) to the VBUS line as well? The design needs the ability to charge/power the system from the USB-C port in the field (using a USB power bank), the USB-C input is mostly needed for a scenario in which someone forgets to recharge the device after using it and you're left with a low battery starting out a work day. For faster charging however, I'd like to implement a barrel jack input so the device can be charged in a more timely manner as the device is expected to discharge anywhere from 60-90% during the day and the battery isn't small(battery pack is 3S2P 18650 samsung-e35's ~6800mAh). I know the bq2571x can handle said input and the pmp40441 input block and bq25710EVM are extremely similar, so I'm under the impression this will work, but what changes would need to be made (if any) to the pmp40441 input design for this to work properly? Is it simply a matter of programming the MSP controlling the bq2571x to deal with this situation as a barrel jack would obviously not use USB-PD to select input voltage/current?

We don't foresee a situation in which the USB-C will work as an output, however the design does call for a 12V/300mA output for powering an external submeter GPS. In our current schematic this output is enabled/protected by a load switch which takes its' input from VSYS(if using the pmp40441 as reference). With that said our enclosure design necessitates having the IO ports(USB-C/barrel jack/USB-A/EXT12V) on a separate board which will be wired to the charger PCB, in the name of saving money and lowering the number of conductors in the ribbon cable connecting the IO-PCB to the charger-PCB, I'm wondering if I can tie said output to VBUS and use the OTG functionality to provide power? This will save me at least one conductor and I can get rid of a load switch.

As I'm sure you realized I haven't decided which bq2571x to use for this, the battery pack is designed around the bq40z50-r2 which is SMBus and the tusb422 is I2c, but this charging system is ultimately gonna be connected to an existing board which uses an msp430bt5190 as mcu, the sytem-PCB has unused I2C and SPI pins available without any modification. The system is designed to have always-on BT sourcing 3v3 from a second tps70933 on the charger-PCB (so it can be disabled when VSYS goes high, as there is already a 3v3 regulator on the system-PCB and I don't want the two regulators fighting each other) and will enable VSYS and load switches when the device is connected over BT, going into low-power and bringing down VSYS when disconnected.Once connected to BT the bt5190 will tell the fr5949 to bring up VSYS. The msp430fr5949 will be talking to the bq2571x, bq40z50, TUSB422, and instead of led's for charge capacity indication I have opted for an external LCD (I2C and only on for ~30 seconds after a display button is pressed) so I can provide more detailed information without being connected to BT. So thats 1-2 SMBus devices (depending on bq2571x selection) and 2 I2C devices on the same line while also reporting real-time (~1 second update) pack info to the bt5190 so it can be viewed by the user (android tablet running the accompanying app)  Do you have any suggestions here?

Since I'm gonna have to deal with SMBus using the bq40z50 and I2C using the tusb422 does it really matter which bq2571x I use?

Would it be a better idea to use SPI between the bt5190 and fr5949 since I2C/SMBus is already being used for everything else, whichever is used, which msp acts as master?

Should I use the bt5190 to control the LCD since it is already gonna have access to the pack information and also has more memory?  

  • Hey John,

    This is a multifaceted question that may likely require answers from multiple forums, including the MSP low-power microcontroller forum and the Interface forum. 

    I can speak to the BQ2571x portions of your post.

    Without knowing what is programmed into the MSP430 controller to perform the USB PD PPS function and/or detect the input type, the BQ2571x itself will work with a solid 12V input. A controller is still needed to program the charging parameters, input current limits, and any other extra features you want to utilize on the charger. 

    As far a changes, the MSP430 controller on this reference design communicates with the TUSB422 Type-C PD port controller and likely relays information back to the charger to program voltage and current settings. So the algorithm would be the first thing that likely needs some changes to work with a 12V barrel jack. 

    Because you also want to keep the USB Type-C input along with adding the 12V DC barrel jack connection, you will likely need a power muxing circuit; take a look at tte TPS2121 for this. There is a potential for two different inputs to be applied at the same time, so a device like this will effectively diode-OR between your two input source types.

    In regards to using OTG to drive a voltage on VBUS; that is possible. Just keep in mind that you cannot charge AND also use OTG mode. But with OTG mode, you can program the output voltage and current limit settings you want on VBUS. Also note that VBUS will be powered from the battery source.

    As far as communication, you may want to post another question to the MSP430 forum or Interfact forum I mentioned about to give you an idea about those two controllers. As far as the charger, if you want the Gauge to go through the Smart Battery protocol and automatically adjust the charging parameters, then use the SMBus version of the charger, BQ25710. If you don't care for that feature and prefer a fixed charging current and battery voltage regulation setting, then use the BQ25713, the I2C version. In reality, the SMBus data and clock lines can likely be shared with your I2C devices. However, the SMBus device will limit dictate the timing requirements of the bus.


    Joel H