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Original question:

BQ24650EVM-639: Test Procedure 2.7.3 not outputting 0.2A

BQ24650EVM-639: BQ24650EVM-639:

Dave Whitaker
Prodigy 190 points
Part Number: BQ24650EVM-639
Other Parts Discussed in Thread: BQ24650

Hello,

Below is an update I saw regarding the test procedure SLUU444A  for BQ24650EVM.  It says that in step 2.7.1 there is an error where Vout should not be 0V.   However I am not reading 12.6 Volts,    as this customer had stated but rather 4.7 Volts.   At this particular step in the procedure, there is only a supply voltage of 21 Volts on the Vin input and the loads are not on as instructed in step 2.6 ( they are not even connected) .     JP1  is connected between pins 1 and 2,  JP2  is plugged in, JP3 is  connected to pins 2 and 3, and JP4 is  OFF  ( removed ).   Can you explain why I am  getting 4.7 volts on VOUT at step 2.7.1   and  not 12.6 ?   It looks as if you have acknowledged the mistake but it would help me greatly to know what we should be seeing at step 2.7.1  and under what conditions.    I have read your comment number 2 below but I don't understand what it means with reference to the test  procedure.  Please help.

Thanks
Dave

1. The user guide has an error in saying that VOUT = 0V at section 2.7.1. You are correct in measuring 12.6V at this step with a multimeter. This part has a battery absent detection scheme to detect insertion or removal of battery packs. This effect can be seen clearer using an oscilloscope and is explained in detail in section 8.3.21 of the datasheet. Thank you for bringing the mistake in the user guide to our attention.
2. A standard power supply cannot sink current and cannot be used to mimic the load in this case. An electronic load is ideal, however for lower current measurements it is possible to use a Sourcemeter or a Kepco bipolar operational power supply/amplifier. Essentially you require VOUT to be held to a constant voltage and to be able to measure the current into the instrument (CV).
3. Can you describe the conditions in which you see STAT1 illuminate? If you were to remove all load, are you still seeing STAT1 light up?

1. The user guide has an error in saying that VOUT = 0V at section 2.7.1. You are correct in measuring 12.6V at this step with a multimeter. This part has a battery absent detection scheme to detect insertion or removal of battery packs. This effect can be seen clearer using an oscilloscope and is explained in detail in section 8.3.21 of the datasheet. Thank you for bringing the mistake in the user guide to our attention.
2. A standard power supply cannot sink current and cannot be used to mimic the load in this case. An electronic load is ideal, however for lower current measurements it is possible to use a Sourcemeter or a Kepco bipolar operational power supply/amplifier. Essentially you require VOUT to be held to a constant voltage and to be able to measure the current into the instrument (CV).
3. Can you describe the conditions in which you see STAT1 illuminate? If you were to remove all load, are you still seeing STAT1 light up?

  • 0
    TI__Mastermind 24075 points
    Hi Dave,
    When there is no battery connected, this part employs a battery detection scheme to detect battery insertion. Obtaining a waveform at that node would give you more information, and you would see a scope capture similar to Figure 13. of the BQ24650 datasheet. From that waveform you can see battery voltage should rise to whatever you set your charge regulation to. If using a multimeter you would read a DC voltage, so putting it on a scope would give you a clearer picture. For more information on the battery detection algorithm you can refer to section 8.3.21 of the d.s. Comment 2 was w.r.t that customer's specific setup where they were trying to mimic a battery using a power supply, however battery should be able to sink current. Not relevant to the test procedure mentioned in the user guide.
  • 0 in reply to Kedar Manishankar
    Prodigy 190 points
    Thank you Kedar, I understand that step 2.7.1 will show the timing diagram from Fig 13.
    There are several voltage and current measurements stated in the entire procedure with +/- tolerances. Please clarify that the rest of these measurements can be verified with a multi meter. Please understand that the test procedure for the EVM is the only reference that is published to verify its operation out of the box (assuming all jumpers, power supplies and loads are set as outlined). Based on the date that this document was published, I highly doubt that it will ever be updated but please if you can, forward to me any text where steps could be misinterpreted or that are incorrect, if you think they exist.

    Thanks Again,
    Dave
  • 0 in reply to Dave Whitaker
    TI__Mastermind 24075 points
    Hi Dave,
    Currently I am not aware of any other discrepancies in the user guide, but if you happen to run across anything feel free to reach out via E2E, and I can explain or correct the problem. We appreciate the feedback, as we can use this to update these documents in the future, as well as help other customers who might run into the same problem in the future.