TPS65988: About leakage voltage between PP_HV2 and VBUS2 on source setting.

Hi Uchida,

With VIN_3V3 open, the dead battery flag cannot be really cleared, cause PD cannot get power from VIN_3V3; if VIN_3V3 is powered by 3.3 V supply, the clearing of dead battery can have the VBUS2 to 0V.

Hi Bing,

Thank you for your reply.

I clear the dead battery flag by 4CC command DBfg.

Is there risk damage to the TPS65988 and connecting sink devices by leakage voltage?

Hi Bing,

I am concerning very much that my system is VIN_3V3 open.

I have additional questions about “the dead battery cannot be really cleared”.

Q1:Is there risk damage to the TPS65988 by leakage voltage?(same as a previous question)

Q2:Could you tell me all of limited things on “the dead battery cannot be really cleared” ?

Q3:My system clear dead battery flag by 4CC command DBfg. VIN_3V3 is opened.

      Source port of my system have the load switch. Please see the attached figure.

      In my system, the leakage voltage does not occur to TypeC2 port.

      Must I connect VIN_3V3 to 3.3V power supply in my system?

Hi Yasuhide,

Q1:No, this leakage will not damage TPS65988;

Q2: When the device is in dead battery, 1. PD device is powered from VBUS pins; 2.The other port cannot source high-voltage contract to the far-end device. These two points are the mainly impacts from dead battery mode.

Please note that, actually, dead battery flag is used to notice that the system is only powered from Type-C port, although the flag can be cleared by DBfg, however, if VIN_3V3 is not powered by an 3.3V power rail, the powered supply for 988 is still powered from VBUS side.

Q3: As the description from Q2, I recommend add 3.3V supply on VIN_3V3 pin, cause this pin is the only way PD determines the logic of Dead Battery Mode.

If you want to clear Dead Battery Flag, you should set the PD into the situation where it is really in battery-have-state (or PD thinks it is really in battery-have-mode), that is to power the VIN_3V3 pin; otherwise you don't put PD into battery-have-mode and then push it into Dead Battery Mode by using DBfg, I don't think it is reasonable.

Thank you for your great cooperation.

I have additional questions.

Q2: About ”2.The other port cannot source high-voltage contract to the far-end device. ”

      (1)What is high-voltage? Over 5V? (example 9V, 15V, 20V  PD voltage ?)

      (2)Is this limitation only source port?

      (3)Must I clear dead battery flag(4cc or VIN_3V3 connected) for sink port? Are there limited things of sink port in dead battery mode?

Q3: Source port of my system outputs only 5V 3A. Please see the attached FW tool source capabilities setting.

       In this case, Must I connect VIN_3V3 to 3.3V power supply?

Q2: About ”2.The other port cannot source high-voltage contract to the far-end device. ”

      (1)What is high-voltage? Over 5V? (example 9V, 15V, 20V  PD voltage ?)

         In Dead Battery Mode, it can only output 5V/ 0.9A;

      (2)Is this limitation only source port?

        Only on source port. The logic is this: now that the system is in Dead Battery Mode, which means no unconstrained power or battery, so the system should not output high power because which may cause the system cannot get enough power used by itself.

      (3)Must I clear dead battery flag(4cc or VIN_3V3 connected) for sink port? Are there limited things of sink port in dead battery mode?

         If you want to output high power contract you must clear dead battery flag.

        What is the use case for your product? One port used as Sink and the other port used as Source, and I don't see other interface on your design, I could not understand why don't you charge device directly?

Q3: Source port of my system outputs only 5V 3A. Please see the attached FW tool source capabilities setting.

      Your setting is right.

       In this case, Must I connect VIN_3V3 to 3.3V power supply?

     Yes, I suggest that. Because you need to clear the Dead Battery flag.

Thanks.

Bing

Hi Bing,

Thank you.

I am understanding dead battery mode.

But I’m not confident in my understanding is correct or not.

I describe my understanding as below.

Is my understanding correct ?

(1)In dead battery mode, the source port has limitations, the sink port doesn’t have limitations.

(2)In dead battery mode, the source port can output up to 5V 900mA, cannot output high voltage(over 5V) and high current(1.5A, 3A, 5A).

(3)When the dead battery flag is cleared by 4CC command DBfg(VIN_3V3 open), the source port can output up to 5V 3A, but cannot high voltage.

(4)When VIN_3V3 is connected to 3.3V power supply, the source port can output high voltage and high current(20V 5A).

Bing is out of the office for Chineese New Year.  He will address this when he returns.

Hi Bing

Thank you for your great support.

If you have the document about limitations in dead battery mode, I would like to get it.

Please inform me the document about limitations in dead battery mode.

I already read the TPS6598x Dead Battery Application Note(SLVAE65).

But I could not find the detail of limitations in dead battery mode.

Hi Yasuhide,

Actually PD has not many limitations in Dead Battery Mode. What I've described are all.

The reason PD needs to limit source capability in Dead Battery Mode is that: When the system in Dead Battery Mode, we think there is no additional power on the system, thus the only power supply is Type-C.

So in Dead Battery Mode, source capability needs to be limited to ensure that enough power can be provided to system itself to have it work well firstly, and then a little power can be supply to other device through Type-C port. So this is why we limit the source capability in Dead Battery Mode.

Thanks.

Bing