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BQ24296MEVM-655: BOOST Voltage drops at 100mA

Neil Hancock
Prodigy 70 points
Part Number: BQ24296MEVM-655
Other Parts Discussed in Thread: BQ24296, BQ24296M, BQ25895M, BQ25895, EV2400, BQSTUDIO

I'm driving a BQ24296 on a BQ24296EVM - and in boost mode I can only get 100mA out of it before the voltage drops.

How much voltage variation should I expect from 0-1000mA?

On start, I've charged the attached LiIon battery with a strap on JP7 /CE. The LiIon charges to 4.22V, and is fully charged having been there for a couple hours.  

I disconnect power supply on Vin, remove JP7 /CE and  Voltmeter drops to 0

REG00-09    0x37 0x1b 0x60   0x11 0xb2 0x8c 0x73   0x4b 0x84 0x0

Then I put it into boost mode writing BOOST REG01[54]=10 which turns on boost and Vin goes to 5V

Then I write  EN_TERM Reg05[7]=0 so no termination

0x37 0x2b 0x60   0x11 0xb2 0x0c 0x73   0x4b 0xc0 0x0

THen I apply increasing load -for following LOAD=Vin(boosted),  NoLoad=4.97V, 63mA=5.01V 100mA=4.57V, 209mA=4.56V  500mA=4.52V 4.45V=1000mA Lion starts ~4.2V Battery is charged and drops to 4.0V on Load=1A

No Load REG00-09 read (twice)

0x37 0x20 0x60   0x11 0xb2 0x0c 0x73   0x4b 0xc0 0x0

200mA REG read

0x37 0x20 0x60   0x11 0xb2 0x0c 0x73   0x4b 0xc0 0x0

1A Load, LiIon~ 3.95V  and voltage  REG read

0x37 0x20 0x60   0x11 0xb2 0x0c 0x73   0x4b 0xc0 0x0

The Inductor IHLP2020ABER1R0M01 4.4A 46mΩ seems to be specified for it.

  • 0
    TI__Mastermind 46611 points
    Where did you measure the boost voltage? What boost load did you use?

    Thanks!
  • 0 in reply to Ning T
    Prodigy 70 points

    Hello, I'm measuring it on Vin & I repeated measurements with load on PMID/TP2

    I remove the power supply that was charging - as described above- then update the I2C registers to put into boost, read the voltage to verify boost is operating, then apply a restive load.

    The load is 4ohm/50W in series with a heavy duty  variable 75W resistor.

    I adjust the load starting at 79Ohm, measuring the current with a series A meter and Voltmeter.

    I've probed TP5/Bat to see if there is any ripple - but none is visible. Only C7/10uF is on the board The capacitors C18,19,20 are not on the board.

    Appreciate any insights as I'm trying to decide how I can generate the 1A@5V that BQ24296M says it can generate. 

    With all the I2C/monitoring capability in the BQ24296M seems strange there isn't a fault condition that says the voltage generated is outside the requested range.

    thanks

    (added picture of test setup)

  • 0 in reply to Neil Hancock
    TI__Mastermind 46611 points
    Referring to the EVM user's guide p9, 6. Switch to Boost mode, the OTG load should be connected to J2 (PMID+ and GND-) and measure PMID voltage at TP2. Please do not apply OTG load to TP2. Thanks!
  • 0 in reply to Ning T
    Prodigy 70 points
    I'm sorry with all due respect I am following , EVM user's guide pg9 Sect 6(c). I am electrically connecting the load to PMID+ and GND-.
    J2 PMID+/TP2 are the same point electrically - from the circuit diagram and visual inspection of the board.
    I'm really not clear on what direction you are giving.

    I am using a specific TI supplied EVM module for the express purpose of following the manual.
    I am assuming the "Enable OTG" option GUI maps to writing 10 to the OTG_CONFIG/CHG_CONFIG REG01[bit5bit4]
    What bit in the bq24296M registers does the "OTG Low" box GUI map to?

    I am actually also seeing more instability in the output signal than I have stated.
    I have found if I startup the OTG boost first before applying the load it works.
    If I have the load connected first, I have seen the PMID voltage oscillate on a step up/down.

    Thanks
  • 0 in reply to Neil Hancock
    TI__Mastermind 46611 points
    We have ben discussing about OTG mode (also called boost mode), that refers to VBAT as input and VBUS/PMMID as output.
    OTG Low is not link to any register bit, it offers a convenient way to physically pull OTG pin voltage low and high. The boost mode is activated when the REG01[5] = 1 and OTG pin is High.
    The device support up to 1.5A OTG load. Referring to 8.3.5.4.1 of the d/s, there are Q1 and Q3 overcurrent protection implemented. If these overcurrent protections are triggered, the device behaves differently from normal operation.
    Please check Verified Answer if this helps.
    Thanks!
  • 0 in reply to Ning T
    Prodigy 70 points
    Hi this is definitely not solving it for me. I've delayed my hardware desing using the bq24296 until I can verify its functionality or find a similar part.
    There doesn't seem to be anyway that I'm triggering the over-current protection.
  • 0 in reply to Neil Hancock
    TI__Mastermind 46611 points

    Hi, I do not see any problems with the 296M EVMs at my hand.

    1) Did you try on other brand new EVMs? Did you oberseve similar behavior?

    2) Please disconnect your real battery. Just use a lab power supply to support VBAT voltage with a bulk cap, you may set VBAT higher to 4.5V, then try OTG mode following user's guide p9, 6. Switch to Boost mode. After PMID has 5V output, then gradually increase resistor load @ PMID, please check if you get different results.

    Thanks! 

  • 0 in reply to Ning T
    Prodigy 70 points
    I've purchased the bq25895EVM .
    Though it feels like a minefield when reviewing the options, and the EVM strategy ~ hw EVM and Studio looks poorly thought out.
    Also I haven't yet figured out the difference between the bq25895 and bq25895M
    The EV2300 doesn't have direct plugin cable to the 296M EVM, and does for the bq25895EVM. Yeah!.
    The bq2589xEVM manual has mistakes on referencing the bq2589xEVM Battery Management Studio. Its pretty hard finding the BMstudio software. Then its pretty hard figuring out the drivers. eg the download page for BMstudio doesn't have references.
    Finally on digging deeper it turns out the EV2300 has unsupported drivers for windows 10. This isn't stated anywhere with the EV2300.
    Then the EV2400 is double the price of the EV2300 without being clear why.
    So gosh, trying to evaluate the bq family really has a lot of pitfalls in the strategy.
    Overall I do have a BMstudio v1.3.54.1/Windows10 reading the bq25895 device - but I feel lucky that it somehow has worked for me.

    Now I can actually try and evaluate does the bq25895EVM generate a boosted voltage for a specified current like the '296M EVM never did for me.
  • 0 in reply to Neil Hancock
    TI__Mastermind 46611 points

    Thanks for the update. For EV2300, please feel free to install EV2300a_Device_Driver_Installer_Multilanguage.exe  and try again. More details are available at https://e2e.ti.com/support/power_management/battery_management/f/180/t/128220.

  • 0 in reply to Ning T
    Prodigy 70 points

    Thanks - I do have comms with the bq25895Evm, and have it charging/OTG generating.

    The bqStudio has been great to learn what I need to know about the bq25895. Now I've got it connected to my target driving the I2C and looking at the control algorithm I need. Hurrah.!!!! 

    Is there any document that identifies all the members of the bq2589x family and their differences. thanks