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BQ24073: BQ24073 high frequency noise??

kwon
Intellectual 850 points
Part Number: BQ24073
Other Parts Discussed in Thread: TPS2113, , BQ24080, TPS2112

The charger IC(BQ24073) and MUX(TPS2113) are configured to use high voltages as shown below;

The following phenomenon appears;

1) In battery mode, if the battery is at the same voltage, it makes a high frequency noise sound is very weak, and if there is a difference in battery voltage, it does not make a sound.

2) If 5V is applied to two charger IC without batteries, it makes a high frequency noise. The sound is very weak.

3) There is no sound when only one charger IC output(10/11 pin) is connected to the MUX input terminal(IN1 or IN2).

4) There is no sound when connecting the same voltage other than the charger IC output to the MUX input terminal.

I tested by changing various values(ILIM,ISET,TMR), but the same phenomenon appeared, and I could not find the cause of high frequency noise.

Is there anything wrong or corrected in the circuit?

Iinmax=1.36A, Ichg=404mA, charging timer=disable.

  • 0
    TI__Mastermind 23220 points

    Hi Kwon,

    Just to clarify, when you say the battery is the same voltage, are you referring to a battery with each charger (two total batteries)? 

    Can you provide a waveform of the voltage and current at the outputs of both chargers as well as the MUX output?

  • 0 in reply to Anthony P Pham
    Intellectual 850 points

    Thank you for your answer.

    It is a battery in each charger.

    The mux output waveform cannot be captured, consumption current is less than 300mA, and voltage waveform do not have drop or noise.

    As mentioned above, high frequency noise is sound, not waveform.

    In discharge mode(battery voltage output), two chargers have batteries with the same voltage or power input mode(4.4V Output), a sound is generated when two chargers are connected to the mux.

    In case of high frequency noise sound ;

    1) Two batteries have different voltages in discharge mode.

    2) When individually connected to mux in power input mode.

    3) When the same DC power is connected to mux 1/2, not the charger output.

  • 0 in reply to kwon
    TI__Mastermind 23220 points

    Hi Kwon,

    I see no issues with the battery charger configuration. Can you share the waveform of the output of the two chargers when the noise is occurring? How are these being connected to the MUX (i.e. via cables or pins)? Can you try using different cables if they are cables?

    kwon said:

    In case of high frequency noise sound ;

    1) Two batteries have different voltages in discharge mode.

    2) When individually connected to mux in power input mode.

    3) When the same DC power is connected to mux 1/2, not the charger output.

    Is this the same information you provided in the initial post? This seems to be conflicting if you are saying these are the conditions where you are seeing a sound. 

  • 0 in reply to Anthony P Pham
    Intellectual 850 points

    I wrote this wrong. It's a case that doesn't happen. I'm really sorry.

    1. The charger and mux are connected very closely by pcb artwork design. However, the two nets are different in length.

    2. Below is the output  voltage waveform of the charger in charging mode and discharging mode.

    I apologize once again and thank you for your reply.

  • 0 in reply to kwon
    TI__Mastermind 23220 points

    Hi Kwon,

    Everything looks fine from the charger standpoint. Are you able to probe the stat pin of the TPS2113?

  • 0 in reply to Anthony P Pham
    Intellectual 850 points

    Thank you for your answer.

    The mux state(pull-up R)/charger output voltage/mux output voltage were measured together.

    As shown below, noise occurs in the waveform when there is no battery. At this time, high frequency noise sound seems to occur.

    It seems that the output state changes battery insert and no battery.(charger Vout is the same.)

    Is there any difference in bq24073 spec?

  • 0 in reply to kwon
    TI__Mastermind 23220 points

    Hi Kwon,

    It seems that when there is no battery, the switching may be causing a high current draw that would be causing the output voltage to drop enough to the point that the voltage causes the TPS2113 to switch sources. 

    Would you be able to zoom in on the time scale when this occurs to verify?

  • 0 in reply to Anthony P Pham
    Intellectual 850 points

    Wow~!. I learn a lot. Thank you.

    Attach the measured in scope AC mode.

    Because of noise as shown below, I was thinking of configuring BQ24080/TPS2113 instead of BQ27073.

    If there is no battery, it seems that the same noise phenomenon occurs during ON/OFF repeat in U11 MUX. What do you think?

    How can I remove the charger noise? It seems that adding a capacitor to the bq24073 Vout & TPS2112 Vout has little effect.

  • 0 in reply to kwon
    TI__Mastermind 23220 points

    Hi,

    It looks like this may be an issue in the input stability. Are you seeing a similar waveform on the BQ24073 input that you see on the BQ24080? Can you confirm that this behavior doesn't occur when connecting the load directly to the BQ24080 if possible? 

    Does this occur if you increase the capacitor on the IN pin? 

  • 0 in reply to Anthony P Pham
    Intellectual 850 points

    Hi~.

    The above waveform is the enlarged noise at the output of the TPS2113 in bq27073/TPS2113.

    Since the problem is not solved in BQ27073, only the BQ24080 circuit is drawn, so the waveform cannot be measured.

    It increased from bq27073/TPS2113 to 68UF of TPS2113 input/output. It is effective, but noise still occurs.

    Thanks.

  • 0 in reply to kwon
    TI__Mastermind 23220 points

    Hi Kwon, 

    This looks to be a result of an output drop on the device and may not make a difference if you keep changing the charger.

    Can you probe the input of both chargers and share the waveform? Can you also share the output of both chargers and share the waveform?

    I believe there may be a cycle of a high current draw that is occurring on the chargers at different times causing the MUX to switch back and forth between the two. 

  • 0 in reply to kwon
    Intellectual 850 points

    Thank you. I'll test some more.