TPS25751: TPS25751EVM + Bq25756EVM Power Path for PDO 1 PP3 Source Issue

Part Number: TPS25751
Other Parts Discussed in Thread: BQ25756, , BQ25756EVM, EV2400, BQSTUDIO, BQ25798

Tool/software:

Hi Everyone,

I already mention about the problem in here.

 RE: TPS25751: TPS25751EVM + Bq25756EVM Power Path for PDO 1 PP1 and PP3 Source Issue 

I used good boost converter for the supply DRV_SUP and PP5V from 1 Cell application. TPS25751 goes into hiccup mode since the switching sequence and PP5V supply to the VBUS was not managed well in my opinion.

Please check the attachment report which is in detail information about the setup, settings and oscilloscope SS.

I need to find how I will fix this problem. The aim is that use 5V generated from boost converter from 1 cell with limited current 500mA for PP5V connection. I want to supply for 5V/3A source VBUS from PP3.

{
  "questionnaire": {
    "device": "TPS25751",
    "toolBuildVersion": "1.1.1",
    "answers": [
      null,
      0,
      3,
      3,
      0,
      0,
      3,
      0,
      1,
      1,
      1,
      3,
      4,
      3,
      1.536,
      15,
      0.5,
      1,
      0
    ],
    "vendorId": "0000",
    "productId": "0000",
    "version": "1.0.0.2"
  },
  "configuration": {
    "data": {
      "selected_ace": [
        {
          "register": 6,
          "data": [
            84,
            121,
            97,
            66,
            48,
            46,
            49,
            86
          ]
        },
        {
          "register": 22,
          "data": [
            8,
            2,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            3
          ]
        },
        {
          "register": 40,
          "data": [
            2,
            1,
            63,
            79,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            1
          ]
        },
        {
          "register": 41,
          "data": [
            210,
            0,
            144,
            0
          ]
        },
        {
          "register": 50,
          "data": [
            5,
            170,
            42,
            44,
            145,
            49,
            32,
            44,
            209,
            50,
            0,
            44,
            177,
            52,
            0,
            44,
            65,
            182,
            45,
            44,
            177,
            148,
            237,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0
          ]
        },
        {
          "register": 51,
          "data": [
            4,
            44,
            145,
            1,
            16,
            44,
            209,
            2,
            0,
            44,
            177,
            4,
            0,
            44,
            65,
            6,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0
          ]
        },
        {
          "register": 55,
          "data": [
            118,
            192,
            18,
            5,
            144,
            145,
            193,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0
          ]
        },
        {
          "register": 66,
          "data": [
            10,
            0,
            8,
            0
          ]
        },
        {
          "register": 92,
          "data": [
            13,
            12,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            4,
            0,
            0,
            0,
            4,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            75,
            73,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0
          ]
        },
        {
          "register": 112,
          "data": [
            3
          ]
        },
        {
          "register": 119,
          "data": [
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            4,
            1,
            45,
            0
          ]
        },
        {
          "register": 120,
          "data": [
            0,
            0,
            0,
            128
          ]
        },
        {
          "register": 122,
          "data": [
            0,
            0,
            0,
            0
          ]
        },
        {
          "register": 123,
          "data": [
            0,
            2,
            255,
            255,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0
          ]
        },
        {
          "register": 125,
          "data": [
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0
          ]
        },
        {
          "register": 126,
          "data": [
            0,
            0,
            0,
            0,
            0,
            0,
            1,
            0,
            0,
            0,
            0,
            0,
            0,
            0
          ]
        },
        {
          "register": 152,
          "data": [
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            0
          ]
        }
      ]
    }
  }
}

Problem Detail 11092025.pdf

  • Hello,

    Thank you for the detailed report.  I have also reached out to the BQ team regarding why the 4.7V on DV_SUP works but 5.0V does not.  

    Regards,

    Chris

  • Hello,

        Do you have the ability to increase the capacitance on the DRV_SUP and also retest with the LDO replaced with a stronger 5V to see if the issue is with the DRV_SUP.

        Also, in the 5V case (vs the 4.7V) do you see anything from the PD controller writing to the BQ?  I am curious in the transition from PP5V to PPHV if the PD thinks there is a reverse current event and the 4.7V does not trigger.

    Regards,

    Chris

  • Hi Chris,

    I’m using programable psu 4.7V or 5V supply. I also dont see any dropout in the oscilloscope. I draws 30ma to 300ma. No dropout also in the ldo 3.3v.

    I will sniff Monday morning between bq and pd update in here. Actually the main problem in my opinion is that pd enable vbus before not the enable switching on bq. It cause immediate drops on the vbus then bq sense the vac drops (most probably short circuit or overload) pd goes into the hiccup mode.

    Why 4.7v not effected this situation, it might be usb pd protocol don’t allow the enable vbus since the uvp. When the transection is finished vbus supply coming from bq 5v pd on the vbus enabled.

    is it possible such a this scenario? Is it possible to setup and test it with 1cell with nominal 3.2v? Do you have facilities to simulate in your lab?

  • Hİ Chris,

    Here is the communication sniffer data for PP5V supply with 4.7V and 5.0V.

    During supply with the 4.7V the source is starting to charge successfully and here is the data;

    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 

    When I set supply with the 5V for PP5 the source is goes into the hiccup mode and here is the data;

    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x19 0x40 
    write to 0x6B ack data: 0x17 0xCC 
    write to 0x6B ack data: 0x0C 0x04 0x04 
    write to 0x6B ack data: 0x0A 0x4C 0x00 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x17 0xC8 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0C 0x10 0x04 
    write to 0x6B ack data: 0x19 0x01 
    write to 0x6B ack data: 0x0A 0x04 0x01 

  • Hello,

    I will reach out to the BQ team and recreate the setup on my end.

    Regards,
    Chris

  • Hello,

    I’m using programable psu 4.7V or 5V supply. I also dont see any dropout in the oscilloscope. I draws 30ma to 300ma. No dropout also in the ldo 3.3v.

    Can you provide some images?  with and without additional capacitance on DRV_SUP.  The testing on my side is a little more involved than i had planned and need to have some additional justification.

    Thanks for your patience.

    Chris

  • I added 470uF at DRV_SUP pin and here is the pictures with 4.5V supply (working) and 5V supply (hiccup) pictures. You can see there is no dropout at the DRV_SUP pin.

    CH1: VAC (yellow)

    CH2: DRV_SUP (Blue)

    CH3: VBUS (Purple)

    DRV_SUPP=4.5V No Cap

    DRV_SUPP=4.5V No Cap (Zoom)

    DRV_SUPP= 5V No CapDRV_SUPP= 5V No Cap

    DRV_SUPP= 5V, Cap=470uFDRV_SUPP= 4.5V, Cap=470uF

  • Thank you.  I am going through the modifications and noticed some differences.  Can you confirm what revision of the EVM you have?  I am looking at BMS042C in the upper right corner.

    Regards,
    Chris

  • BQ25756 EVM --> BMS042E4
    TPS25751EVM --> IPP009 Revision A1

  • Hello,

    Thanks.  I will see if i can find a detail of the differences in the EVM revisions.

    Regards,
    Chris

  •   is there any update? Did you test the same setup 1cell configuration with the TPS25751EVM? Is it working in your side?

  • Hello,

    I am still investigating.  It is not working on my side, but I am seeing a much more pronounced deviation on the 5V source and the resulting dip in VBUS.  I will work to see if I can clean that up with more capacitance and confirm that the PD is going through a disconnect sequence due to the UVLO threshold being crossed.

    Regards,
    Chris

  • Hi Chris,

    The graph that you mentioned, VBAT was increased even the DRV_SUP tries to switching. How possible? PP3 was selected for the PDO1 right? 

    Additionally, I found a supportive clues that the PD timing issue. When I checked the PD Status Register 0X40 during supplying the DRV_SUP=5V and PP3 for PDO1, during the hiccup mode, I get below massages.

    70 00 40 0B

    Hard Reset Details (bit21–16)

    • Byte2 bit5–0 ve Byte3 alt bitleri → 0x40 0B

    • Byte3: 0x0B → 00001011 → Hard Reset Details = 0x0BSourceOnTimeout

    This time interval is short and result as restart always. At that monent, When I disconnect the ribon cable between TPS25751EVM and BQ25756EVM the source mode is started successfully. Is there any way to increase this wait source on time not to trigger hard reset?

  • Hello,

    VBAT was increased even the DRV_SUP tries to switching. How possible?

    The BQ part is outside of my area of expertise.  I am using a power supply to provide the 3.2V.  

    PP3 was selected for the PDO1 right? 

    Correct.  I am using the configuration file you provided.

    Is there any way to increase this wait source on time not to trigger hard reset?

    I am looking into this.

    Regards,

    Chris

  • Hello,

    Can you test your system without the TPS25751?  Specifically, send the I2C commands to the BQ using an I2C tool and measure how long it takes for the 5V to turn on?

    Regards,

    Chris

  • Hi Chris,

    I disconnected the ribon cable and used the BQStudio with EV2400. I clicked "EN_REV" to ON of the VBUS. Here is the graph.

    Purple is the SMBUS SDA pins coming from the EV2400.

    Yellow is the VAC.

    Blue is the VBUS. 

    The time interval command to the VBUS 1.6sec and after VBUS high 100msec later VAC is activated. As you see from the graphs when the command is sent at the time curssor "a", the fist trying is failed and the second one is successfully set.

  • Hello,

    I will need to confer with the BQ team.  The PD spec requires to provide VBUS within 275ms, so waiting for 1.7 seconds is not feasible.  

    Regards,
    Chris

  • Hi Chris,

    I was saying at the begining of this thread. This is the sequence issue in my opinion. PP5V is already supplied on the TPS25751 even the less current limited. When we select Power Path for PDO 1 PP3 Source, the sequence is supplied from PP5V with short duration. The only things to do not activated the VBUS until the conversation is finished from BQ25756 side. When the PD see the voltage level 5V on the VAC, then activated the VBUS, then the source can cause immedialtely drop on the VBUS since the there is no switching.

    I think the TPS25751 must be check from BQ via communication switching started or not, not the voltage level of the VAC. This phenomena can explain why this system is also working 4.5V supply. When we supply 4.5V to the PP5V and DRV_SUP, TPS25751 not enabled the VBUS since the VBUS voltage under 4.75V, then the BQ25756 is started to switching 5V is seen  at the VBUS and TPS25751 is activated VBUS successfully.

  • Hello,

    I think the TPS25751 must be check from BQ via communication switching started or not, not the voltage level of the VAC. This phenomena can explain why this system is also working 4.5V supply. When we supply 4.5V to the PP5V and DRV_SUP, TPS25751 not enabled the VBUS since the VBUS voltage under 4.75V, then the BQ25756 is started to switching 5V is seen  at the VBUS and TPS25751 is activated VBUS successfully.

    But the VBUS is enabled when the supply is 4.5V.  You can see it is 4.5V here.

    Regards,
    Chris

  • There is a misunderstanding about the phenomenon, let me clarify it. I believe that PP3 and PP1 have a sequence order to supply PDO1.

    Under normal conditions, PP1 supplies the bus. We can observe that 4.5V and 5V VBUS are activated by PP5V. S1 remains closed and continues supplying until the required VBUS is enabled.

    While supplying 4.5V, if no voltage detection or protection is triggered on the VBUS, S1 stays closed and keeps supplying VBUS. This voltage level is less than 4.75V, which provides some time for the switching delay coming from PPHV. At that moment, the PPHV voltage level is also below 4.75V. Then, we can see a step-up at the VBUS level, and it starts successfully.

    When supplying 5V, at the initialization stage PP5V starts supplying VBUS, as already observed. Once initialization begins, PPHV immediately reaches 5V, and the TPS25751 causes S1 to open and S2 to close. As a result, the load consumption immediately decreases the voltage on the VBUS.

    If somehow S1 not closed imediately or wait a moment a little bit the problem will be solved. I research also why the S1 is closed, we may trigger RCP but I'm not sure about this.

    "If VVBUS - VPP5V > VPP_5V_RCP, then the PP_5V path is automatically disabled within tPP_5V_rcp. If the RCP condition clears, then the PP_5V path is automatically enabled within tON."

    PP5V = 4.5V

    PP5V = 5V

  • Hello Ali,

    Thanks for being patient with this.

    I'm rereading through your schematic and I saw you are using a single LFP cell with a max voltage of 3.2V. I misread your first post and thought you were using a 4.2V Li-Ion cell.

    The BQ25756 will have difficulty starting reverse mode if the battery voltage is 3.8V. We recommend that the battery should be above 3.8V before starting reverse mode. I am working to update the BQ25756 datasheet to reflect this.

    I have a few recommendations to get around this behavior:

    • I don't recommend this, but you can start reverse mode with a battery voltage below 3.8V by applying a 5V voltage to REGN.

    • Can you swap the LFP cell for a Li-Ion cell?

    • Can you use 2 LFP cells in series?

    • Could you use the BQ25798? This part will be better suited to charge a 3.2V battery.

    Once again, thanks for being patient with this.

    Best Regards,
    Ethan Galloway

  • Hi Ethan,

    First of all I can't use BQ25798 since the current 5A is not enough for this project. We aim the get 60W USB PD power.

    Only 1S LFP will be used size,current and wh requirements. 

    Actually the BQ25756 is starting within the interval 2seconds. If I used PP1 for PDO1 there woouldnt any problem. Is somehow I can change SourceOnTimeout parameter or sequence swittching architecture modification as written at the above side S1 and S2, the problem will be solved.

    Could you please share with me in detail how the TPS25751 working when we select PP3 source for PDO1. PP5V and PPHV which exact time open and close. What is the parameter and decision variable to set PP5V open then PPHV closed? If I find work around solution I may implement it. 

    Additionally, the BQ25756 there is no direct supply from VBAT. The only connection is VFB. It should not be a problem for 1 cell application to supply DRV_SUP and the REGN does not used in my design.

    The only consideration is VAC sense at the initialization, before switch, the IC is only checking the Vov,Vcuv or shortage.

    I will try in my board with 2S option and inform you how will effect.

  • Hi Chris and Ethan,

    I tried 7.2V VBAT and it was worked. When atteachment on the load SW1 is starting imediately switching before VBUS enabled. If we supply 3.3V VBAT, there is no switching at the SW1 :( Why it's not switching, why is not starting whats the real reason?

    Yellow VAC

    Blue VBUS

    Purple SW1

    At VBAT=7.2V

    At VBAT = 3.3V

  • Hello Ali,

    Additionally, the BQ25756 there is no direct supply from VBAT. The only connection is VFB. It should not be a problem for 1 cell application to supply DRV_SUP and the REGN does not used in my design.

    The BQ25756 gets initial power from SRN (which is tied to the battery voltage) when starting reverse mode.

    REGN is used to power the internals of the BQ25756.

    DRV_SUP provides power to the gate drivers.

    Why it's not switching, why is not starting whats the real reason?

    The IC doesn't have enough voltage to start switching with only a 3.3V battery source.

    I'll let Chris respond to the questions for the charging characteristics.

    Best Regards,
    Ethan Galloway

  • Hi Ethan,

    I see in the block diagram. The last question for this issue. What happens if I supply REGN with external 5V? Is the LDO have reverse protection diode for the supply side(Vac and Vsrn)?

  • Hello,

    There are no hooks or parameters made available to change or control the power path timing.  These are set in the device to comply with the USBC-PD specification.

    Please refer to the following for your reference:

    PDO1 is set to PP3.

    Time from connection to presentation of VBUS(PP5V) ~3.6ms

    Time from connection to switch from PP5V(PP1) to PPHV(PP3) ~100ms

    Regads,

    Chris

  • Hello Ali,

    What happens if I supply REGN with external 5V? Is the LDO have reverse protection diode for the supply side(Vac and Vsrn)?

    The IC should have reverse protection to the supply side (VAC and VSRN) from REGN.

    I think you can make the circuit work by only applying 5V to REGN when starting reverse mode and then disabling the external 5V afterwards. Let me know if this will work for your system.

    Best Regards,
    Ethan Galloway

  • Hi Ethan,

    I added load switch circuit as can be seen from the below picture

    CH1-Yellow: VAC

    CH2- Blue: SW1

    CH3-Pink: VBUS

    CH4-Green: REGN

    With this circuitry, PP3 Source for PDO1 was worked successfully. The only consideration about applying DRV_SUP during VAC is less than 5V can cause any damage or is this have any disadvantages?
    whats your opinion?