• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 486 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25886: Low Power During Charging

user6310179
Prodigy 180 points
Part Number: BQ25886
Other Parts Discussed in Thread: , BQ25887, BQ25883

Hello, 

We have developed a 2 Cell BMS multilayer board design and have assembled 3 working prototypes shown in the picture below. I have also attached our schematics of the project. The middle schematic is where the BQ25886 comes in. We integrated it into our design with the same design that the datasheet shows and also have the PCB routes as wide as possible near the power path of the BQ25886 chip. When we plug it into a 5V source it only outputs 150mA. I am wondering why it will not go into CC CV mode. 5V @ 150mA is not enough power to charge the battery in a reasonable time. 

How long do you have to wait for it to go from precharge/trickle charge/CC/CV? Can TI see any error in our design why this thing is not charging when it is plugged into 5V.

Thank You

  • 0
    TI__Genius 11850 points

    Hi,

     

    Please refer to the schematic checklist document below. In particular, your schematic is missing capacitance on SYS and BAT. This is required even if you don't have a load connected to SYS.

     

    0005.BQ2588x Schematic Checklist.pdf

     

    Also, note that with the D+ and D- pins floating, the BQ25886 will detect an unknown adapter and set the input current limit to 500 mA. Please see Section 8.3.3.2 in the datasheet for more information about the input source type detection.

     

    Finally, the BQ25886 will not begin fast charging until VBAT rises above VBATLOWV (typical value of 6V). Before that, the BQ25886 will pre-charge the battery with only 1/10 of the fast charge current setting.

     

    Best regards,

    Angelo

  • 0 in reply to Angelo Zhang87
    Prodigy 180 points

    Thank you for the helpful information. We will incorporate that into our next design for this charger. Can you explain why it will not take an input current higher than 150mA at the moment? 

  • 0 in reply to user6310179
    TI__Genius 10240 points

    Hi there,

    This needs debugging of the board to find the charger status and operation mode. The ideal case would to have a evaluation module (EVM) for comparison. 

    Best regards,

    Eric 

  • 0 in reply to ezhao
    Prodigy 180 points

    Thank you. We do not have a BQ25886EVM but we have a BQ25887 EVM. 

    On another note: How do you program the charger using the D+ and D- pins. I see the tables near 8.3.3.3 on the data sheet. How would you program in divider 1-->2.1 amp input current? 

    Thank You,

    Brendan

  • 0 in reply to user6310179
    TI__Genius 11850 points

    Hi Brendan,

     

    The non-standard adapters (such as Divider 1, which has an input current limit of 2.1 A) have proprietary divider values which set specific D+ and D- voltages during the charger's input source type detection. These dividers are on the adapter side, and this isn't something that you would program into the charger.

     

    If you would like to set an input current limit of 2.1 A with the BQ25886, then I suggest connecting a 529 Ω resistor from the ILIM pin to GND, and shorting the D+ and D- pins together so that the BQ25886 detects a DCP. The actual input current limit is set by the lower value between the ILIM pin and the input source type detection. In this case, the ILIM pin limits the input current to 2.1 A. The ILIM pin equation is IINMAX = KILIM/RILIM, as described in Section 8.3.9.

     

    Alternatively, if you use a host-controlled charger such as the BQ25883, this provides the flexibility to change parameters such as the input current limit on the fly via I2C register writes.

     

    Best regards,

    Angelo

  • 0 in reply to Angelo Zhang87
    Prodigy 180 points

    Hi Angelo, 

    I have attached an updated schematic with the changes made to the BQ25886. Do you think when plugged in this module will now provide the maximum current of 3A @ 5v? 

    Thank You,

    Brendan 

  • +1 in reply to user6310179
    TI__Genius 11850 points

    Hi Brendan,

     

    Yes, your circuit should allow 3A of input current. The D+ and D- pins are shorted together to indicate a DCP, and the ILIM pin is shorted to GND, which sets the input current limit to the maximum.

     

    Best regards,

    Angelo