bq24190 - Sharing D+/D- USB lines with host

Hi,

I have the same question.  It is unclear if the device is suitable for daisy-chaining the DP/DM lines.  For example, PORT <--> BQ24190 <-->TUSB1210.  There is an I2C controllable parameter, DPDM_EN (REG07[7]), but the datasheet lacks guidance on the impedance of the DP/DM pins in the 2 modes.  I looked into ordering the EVM, but it did not support a pass-through connection scheme.  I guess I could tap into JP6 and carry the connection forward just as a test to see if maybe LS or FS USB communication can occur.  I suspect HS is out due to signal integrity issues because of the effective stub length on the EVM leading to the BQ24190.

I see a few alternate scenarios:

-- (3-package solution) Add a USB switch with charger detection (TI sells some) and shift to the BQ24192/BQ24193.  The 2nd port of the switch would be empty or you can use it for some other 'feature'.  The BQ24192 should still start up in the DC-only power situation (battery undervoltage or battery disconnected scenarios) with PSEL and OTG controlling the initial current.  What you connect these pins to is dependent on the IC you use because the pins names vary.  Is this resonable, TI?

-- (3-package solution) Add a USB switch without charger detection and use the switch to change between the BQ24190 and your transceiver.

-- (2-package solution) Use TUSB1211 + BQ24192/BQ24193 instead, but this may require more information than is posted in the available TUSB1211 datasheet and may require an active operation from your microprocessor to configure the charger detection routines.  This is how the SMSC parts with RapidCharge do it (all via the ULPI bus and the charger detection needs to be disabled for USB data).  (Also, usually TI includes a note that a more complete datasheet is available, but that is not the the case in that one.  I did not know additional information was available until there was an E2E post on the part.)

I reached more or less the same conclusions ; the datasheet does not specify much regarding the D+/D- pins, not even the parasitic capacitances. Like you do, I suspect it would probably work in practice for Full-Speed mode, but since it is not specified I wouldn't rely on it (and it would probably be a problem if you wanted to apply for the official USB certification, anyways).

I ended up choosing the first alternative you mention ; one advantage is that there is a much wider choice of power management ICs if the charger detection is handled separately.  In particular, some PMICs have one or several integrated buck (or even buck-boost) converters, whereas the bq2419x is boost-only (which is not very useful if you need regulated 3.3V, for example).

USB switches, some of them with charger detection : TI Home > Switches and Multiplexers > USB Switch

Power management ICs : TI Home > Power Management > Power Management Multi-Channel IC (PMIC) Solutions

The topic was started on Feb 25 and still no reply from TI.

I have the same question about suitable solution for daisy-chaining the DP/DN lines of BQ24190 and MC with embedded USB, for example, MSP430F5659 with USB Full Speed (12MHz).

This is something I would also like to know.

The datasheet could also be clearer. In particular, better description of the I2C options in the register tables, rather than having to dig through the next 14 or so pages to find out what exactly a particular bit does.

The D+/D- lines are used by the charger IC in the first 100ms of applied 5V power to determine if the D+/D- lines are shorted or biased as a high power port, and if so sets the input source as an adapter, otherwise it is treated as a USB source.  The charger IC does not enumerate with the host.

The lines can be used in parallel for our IC and a USB transciever in the device, for lower communication speeds, but may be an issue at the high speed communication.  As you probably know, at high speeds unless the impedance of the lines is matched, with good layout techniques, one will get reflections that will be an issue. I am not an expert in this field, but do know that the communication lines are disconnected in the IC after the detection test is finished and possibly using some series resistance will help terminate the line through the capacitance of the disconnect FETs.  I can't be much more help, but would like to know what your application is and how the process developes.

Since each customers board is different, TI has left this testing to the developer. 

Most applications use a power path charger that powers the device's tranceiver on application of the 5V source so the IC with D+/D- is not needed.  For very low end designs with no USB communication, that want to use the USB port as just a power source, this part works well.

Let me know your thoughts.

Charles,

Thanks for reply.

I designed a couple of dozen devices with full and high USB sped and know how to do it.

The question is about using (or limitations) the bq24190RGER (or other TI's chargers) with charging current up to 1.5A from USB ( USB Battery Charging Rev. 1.1 and 1.2) and FULL speed USB communication between a PC and MC in the device simultaneously (or shearing / splitting D+/D-).

Of course I can prototype the device and make a decision. It will take time and efforts of hardware and software engineers. I think, the reliable, easiest and fastest way to discuss the question with engineers. Also I have another option: to use another company ICs and discuss this question with that company engineers.

Best regards,

Myron

The USB detection is to decide what input current limit the IC should set on power up as per table 2 in the data sheet.

At any time a host can program the input current limit from 100mA to 3A.  The output current is basically the input voltage divided by the battery voltage times the efficiency so it will be somewhat higher than the input current limit.

I am not sure what you concern is about the 1.5A from USB??  From the point of view from the power supply , the charger is capable of delivering all the input power to the output at a good efficiency, assuming the IC is programmed correctly.  The TI part also have may safety and protection features that seamlessly keep the system powered either by the input source or the battery.

As far as the D+D- communication line design, you seem to have good experience and would expect you to pick the best part for your application.  I do not have any high speed USB communication application "eye' charts, with our charger's D+D- pins connected or I would share it with you. 

Does your application have a USB tranceiver? Is it powered from the SYS output?  Can the tranceiver communicate with the USB host? Do you need the D+D- detection?

Will the bq24192 work for you?

Charles,

CM: The USB detection is to decide what input current limit the IC should set on power up as per table 2 in the data sheet.

MS >> I know it and I did not ask about it.

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CM: At any time a host can program the input current limit from 100mA to 3A.  The output current is basically the input voltage divided by the battery voltage times the efficiency so it will be somewhat higher than the input current limit.

MS >> I know it and I did not ask about it.

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CM: I am not sure what you concern is about the 1.5A from USB??

MS >> This is not my concern and I did not ask about it.

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CM: From the point of view from the power supply , the charger is capable of delivering all the input power to the output at a good efficiency, assuming the IC is programmed correctly.  The TI part also have may safety and protection features that seamlessly keep the system powered either by the input source or the battery.

MS >> I know it and I did not ask about it.

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CM: I do not have any high speed USB communication application "eye' charts, with our charger's D+D- pins connected or I would share it with you.

MS >> My question was about FULL speed USB communication (not about HIGH speed) with a charger and USB host connected together to the same USB port (D+/D-).

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CM: Does your application have a USB transceiver? Is it powered from the SYS output?  Can the transceiver communicate with the USB host? Do you need the D+D- detection?

MS >> Yes, it has a USB transceiver. Yes, it is powered from SYS output.  Yes, the transceiver communicate with the USB host (ideally using the same USB port as a charger). Yes, I need the D+D- detection.

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CM: Will the bq24192 work for you?

MS: This is my question. The DS does not say anything about using this charger with a USB host connected to the same USB port. My USB host is MSP430F5659IPZR.

Thanks,

Myron

The TI chargers without D+/D- detection, 98% of them, are basically power stages that work as programmed.  There are parts with hardward components that program and ones with I2C that can program them.

In the case of the bq24192, it has I2C communication and in your case you would use the device's tranceiver to try and communicate with the 5V souce when it is plugged in and determine what source was applied and then the tranceiver/process would tell the charger IC via GPIO to PSEL and OTG pin if it is an adapter or USB and use I2C to program the desired features...input/output current and voltages.

I must have read more into your question than you were asking since people for years have been using the power souce from USB and eithernet without using the communicaiton portion of the cable.

All of our ICs for years are just power conversion device that take input power and charge a battery safely.  A USB power source is no different than any other input source (as far as the charger is concerned), other than it has a different set of programmed threshold to operate within than other power sources.

This basic information is easy to find in any TI charger DS. Thanks for the useless answer.

Thank you for you kind response.