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BQ24253: Heating issue on BQ24253

Muthu S
Intellectual 720 points
Part Number: BQ24253
Other Parts Discussed in Thread: BQ24266, LMR14030, BQ25606

Dear Sir/Madam,

We were using BQ24266 in our circuit, as it is NRND we have replaced the BQ24266 circuit using BQ24253. Attaching the schematic for the battery charger page.
The IC is heating when applied 8.2V@1A, and 8.2V@2A.
L2 Inductor part number is  SRP5030CA-1R0M

for testing we have not connected the battery. D+ and D- has not connected as it is not required for our applications. We need stand alone mode not IIC mode. Input 8.2V (+12v identifier name) is fed from LMR14030. But the actual input voltage is changed to +8.2V. Its not 12V.

Please help to identify the heating issue cause.

Regards,

Muthu SVST_Battery Charger.pdf

 

  • 0
    TI__Guru**** 152426 points
    Muthu,

    The BQ24266 was made NRND because we have a new standalone charger, the BQ25606, to replace it. We have not yet NRND'd the BQ24253 because of its unique shipmode feature but it will likely be NRND'd in the near future. As a reminder, even though a device is NRND, TI's current policy is to not obsolete the IC as long as there are orders for the IC.

    Regarding the BQ24253, the schematic looks okay except for the floating D+/D- lines. I suggest shorting them together. With regards to the heating issue, is the IC properly soldered to a ground plane? Can send a scope shot on 1us/div time scale of SW, SYS, VIN and BAT? Also what are the DC voltages at VDPM, ILIM and ISET?
  • 0 in reply to Jeff F
    Intellectual 720 points

    VST_Battery Charge1.pdfDear Jeff,

    Updated the schematic as per the inputs and we have tested the updated circuit.

    We have made few more modifications as per requirement. Please refer the schematic for updates.

    • R13 and R14 changed from 274K and 100K to 100K and 47K respectively.

    • Short circuited the DP and DM pins in board.

    • Changed Vin from 8.2V@2A to 6.3V@2A ( output of LMR14030, it acts as input buck from vehicle battery)

    We are using one 3.7V 1500mAh Li-Ion battery.

    After making above mentioned modifications

    • VDPM is 2.02V (measured on DMM).

    • I-Vbat is 3.99V - without battery.

    • VSYS is 3.99V without battery.

    • VSYS is 4.09V

    • I-Vbat is 4.09V

    Connected the battery with @ 3.59V for checking the charging. But the battery was not charging.

    • LED2 Is turned ON after power up, but gets off after a couple of minutes.

    • LED1 is turned off automatically after few minutes.

    • VDPM measured is 2.02V

    • VSYS is 3.67V

    • I-Vbat is 3.65V

    • VSW is 3.67 V

    • ViLIM is 1.3mV

    • VIset is 210mV

    Please help to address.

    Regards,

    Muthu S

  • 0 in reply to Muthu S
    Intellectual 720 points

    Dear Jeff,

    Can you please help to resolve this issue?

    Regards,

    Muthu S

  • 0 in reply to Muthu S
    TI__Guru**** 152426 points
    Muthu,

    Is the ICs powerpad properly soldered down to a ground plane, most likely through vias to the bottom of your board? The ground plane is required in order to properly heat sink the board.

    I do not understand the V(ILIM)=1.3mV measurement. ILIM is essentially at ground which means ILIM=2A but you have resistor to ground. What is the load on VSYS? Could it be so large that it is stealing all of the current from the battery? What is your inductor's saturation current spec?

    What are the voltages at TS pin and LDO pin?

    Is the charger's buck converter switching? If you use an oscilloscope to measure V(SW) do you see a squarish waveform? If you use an oscilloscope to measure VSYS when battery is not attached, does it show the battery detection waveform as shown in datasheet figures 1 and 2?

    Also, I am confused as to why /PG LED turns off but VDPM=2.02V. With VDPM that high, the input voltage should be high enough for the charger to report power good through the /PG pin.