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BQ24192I: BQ24192I / BQ24192 can seem to achieve 4A charge

Andy Long68
Prodigy 40 points
Part Number: BQ24192I
Other Parts Discussed in Thread: BQ24192

Hi TI guys,

I wondered of if you can shed light on a couple of questions regarding problems I have. Firstly, can you explain what the difference is between the BQ24192  and BQ24192I. From what I can see reading the data sheet, it's the default values being different and the pre-charge current on the BQ24192I is limited to 640mA max. Other than that, can I assume that the BQ24192I can be configured to deliver a charge current of up to 4.5A?

OK so here is my main issue. I am using the BQ24192I in a configuration as per the application note design within the datasheet whereby the input ILIM is set externally to limit to 3A (177R) as is the  charge control register. I have disabled the watchdog for now, so custom I2C settings do not revert back to defaults. The input source is an adapter capable of delivering 4A @ 5V, so this I feel is more than adequate, however, if the batteries (Li-ion single cell 4 in parallel, totalling 13,400mAh) are taken down to just below 3V, say 2.9V, and a charge cycle is started, once over pre-charge, the maximum current seems to be 1.7A. Why is this when everything indicates settings wise that it should charge at 4A

This is what I write to the registers via I2C on power up:

REG 05 =  default value & b11001111 - Disable watchdog

REG 04 =  b10110001  - Set charge voltage to 4.208V

REG 02 = b11100000 - 4.096A

REG 00 = b00111111 - 3A

REG 06 = b10110111 - 50mOhm as there is a series Isense resistor for fuel gauge, VClamp to 80mV and Thermal regulation to 120deg. C. (Tried this left as default, didn't make much difference)

REG 03 = b00110011 - 512mA pre-charge and termination current.

I'm monitoring the thermal regulation bit (1) in REG 08 and this is not being set.

Please can you help as I'm out of ideas!

Many thanks.

  • 0
    TI__Mastermind 46611 points
    Hi,

    Yes, you are correct. BQ24192I can support charge current up to 4.5A.

    1. What is the VBUS pin voltage when you are testing the charger with the 5V adaptor?
    2.Instead of using a 5V adaptor, please use a regular lab supply for VBUS. Please increase the VBUS voltage from 5V to higher and check if the charge current goes up.


    Thanks,

    Ning.
    Please click "This Resolved my issue" button if this post answer your question.
  • 0
    TI__Mastermind 25800 points
    Hey Andy,

    In regards to the BQ24192i vs. the BQ24192, you are correct that certain default values have been modified to give customer flexibility in charger selection for default parameters.

    When you get over the pre-charge threshold, can you measure the voltage on VBAT as measured from the pin?

    Can you also tell me your register read data for REG 01, 08, and 09 when you transition to fast charge?

    It could be that the charger is immediately entering into CV mode and the charge current is tapering off.


    Regards,
    Joel H
  • 0 in reply to Ning T
    Prodigy 40 points

    Hi,

    Thank you for your reply.

    I did try an lab supply, set to 12V, but no change to the current. I am in the process of doing some testing, I'll collate the  results and post back.

    Andy

  • 0 in reply to Joel Hernandez II
    Prodigy 40 points

    Hi TI guys,

    Ok, so I've done some tests which is the reason for a delayed response.

    I found a couple of possible issues in my settings however there is a strange behaviour in that the host sends all values to the BQ24192i on power up. However, when the adapter is plugged in, REG 0 IINLIM bits are set back to default! in the case of BQ24192i 0x101. If I the write to REG0 again on detecting the adapter (PG), then the current increases to 2.7A. Not the 4A I was hoping, but then swapping to a lab PSU and increasing the voltage to 6.2V The current climbs to near 2.9A before thermal shutdown. So obviously my thermal plane is not sufficient for the latter issue, but is it normal for the input current limit to reset to default on adapter detection/charge?

    Also, I don't seem to observe any pre-charge when the battery is at 2.9V which is what I would have expected.

    Here are the register values in various test scenarios:

    Test Scenario Fully Charged VBATT 2.90V
    (Before Charge Start)    		 VBATT 2.90V
    (Charge Start)    		 VBATT 2.90V
    (Charge Start)    		 VBATT 2.90V
    (Charge Start)    		 VBATT 2.90V
    (Charge Start)
    REG Values Values Values Values Values Values
    00 0x3F 0x3F 0x3D 0x3F 0x3F 0x3F
    01 0x1B 0x1B 0x1B 0x1B 0x1B 0x1B
    02 0xE0 0xE0 0xE0 0xE0 0xE0 0xE0
    03 0x33 0x33 0x33 0x33 0x33 0x33
    04 0xB2 0xB2 0xB2 0xB2 0xB2 0xB2
    05 0x8A 0x8A 0x8A 0x8A 0x8A 0x8A
    06 0xB7 0xB7 0xB7 0xB7 0xB7 0xB7
    07 0x4B 0x4B 0x4B 0x4B 0x4B 0x4B
    08 0xB4 0x00 0xAD 0xAD 0xAD 0xAD
    09 0x00 0x00 0x00 0x00 0x00 0x20
    10 0x00 0x00 0x00 0x00 0x00 0x00
                 
    REMARKS 1. Correct/Expected Values
    2. Battery Fully charged, no charge cycle commences    		   1. 5V 20W Adapter source
    2. No Pre-charge observed.
    3. Charge current 1.8A from start    		 1. 5V 20W Adapter source
    2. Writing input source current on PG    		 1. 5.4 V, 3A Lab power supply source
    2. Writing input source current on PG
    3. Maximum charge current before thermal shutdown 2.85A    		 1. 6.2 V, 3A Lab power supply source
    2. Writing input source current on PG
    3. Thermal Shutdown

    Your comments are welcome especially  regarding IINLIM behaviour and no pre-charge.

    Thanks

    Andy

  • 0 in reply to Andy Long68
    TI__Mastermind 46611 points

    Hi,

    Referring to page 14 of the d/s, after the PG is LOW or REG08[2] goes HIGH, the charger device always runs input current limit detection when a DC source plugs in unless the charger is in HIZ during host mode. After the input current limit detection is done, the host can write to REG00[2:0] to change the input current limit.

    Referring to Table 3 on page 15 of the d/s, the initial input current limit detection sets 1.5A if PSEL is pulled low for 192I.

    VBAT=2.9V is on the boundary of pre-charge to fast-charge transition. Please adjust VBAT and re-test pre-charge.

    REG08=AD indicates the device operates in DPM (9.3.2.2 Dynamic Power Management on d/s). Please check the VBUS, VBAT pin voltages when doing tests and avoid DPM to achieve the desired charge current.

    Thanks,

    Ning.

    Please click "This Resolved my issue" button if this post answer your question.

  • 0 in reply to Ning T
    Prodigy 40 points

    Hi

    Thank you for clarification. That makes sense.