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BQ25770G: About PTM mode

?? ?
Prodigy 10 points
Part Number: BQ25770G
Other Parts Discussed in Thread: EV2400

Tool/software:

1.About PTM,why the inrush current when enabled PTM by register.Otherwise,what is the condition for the swich stop,is the system voltage to reach a value? 

2.What is the condition for the swich enable,is the system voltage to reach a value?

3.After enabled PTM,the charger will exit PTM when exist a heavy load and what is the condition.Otherwise,after exit PTM,when the charger will enter PTM automatically?

  • 0
    TI__Mastermind 31816 points

    Hello ,

    I'm reviewiing your question, I will provide an update by EOW

    Best Regards,

    Christian.

  • 0
    TI__Mastermind 32965 points

    Hi Wang,

    Thanks for your report. Could you list the test conditions of each waveform?

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 10 points

    Hi Tiger,

    Thanks for your reply. All waveform is under PC S0,adapter-65W 4S Battery,Ch1-charger input voltage  Ch2- charger output voltage Ch3- charger input current  Ch4- one charger switch node.

    The first and second waveform test condition:register enable and disable PTM by EV2400 tool.The third waveform:charger output voltage trigged under PC S0.

    Tips:The system power consumption is rapidly changing(from 3.x W to over 65W) under PC S0,therefore the third waveform can obtained by trigger under PC S0.

  • +1 in reply to ?? ?
    TI__Mastermind 32965 points

    Hi, Wang,

    1. there could be some inrush current to charge up the system cap when PTM is enabled. The switching stops when the system voltage reaches the bus voltage. 

    2. the charger operates in buck-boost mode when PTM is disabled, and continues to operate in buck-boost mode until system rail is regulated at min system voltage. 

    3. Yes, when PTM is enabled, the charger will exit the PTM and operates in buck-boost mode if a fault is detected, and resumes to PTM automatically when the fault is cleared. 

    I hope this answers your questions. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 10 points

    Hi,Tiger,

    Thanks for your answer,there are two more questions.

    1.What's the condition for re-entering buck-boost mode after disable PTM by register?From the second waveform,it appears that the output voltage has dropped to a certain value?

    2.In the third waveform,when adapter current is 0,why does charger input voltage exceed the 20V？

  • +1 in reply to ?? ?
    TI__Mastermind 32965 points

    Hi, Wang,

    1. It re-enters buck-boost mode immediately after disable PTM. In buck-boost mode, the switch may stop when system voltage is higher than the min system voltage. 

    2. In the third waveform, the charger exits PTM when the adapter is over-current. Since the adapter current is abruptly cut-off, the energy stored in the parasitic inductance has to go somewhere, it may generate some dynamic voltage on the input cap. You may increase the input capacitance if needed. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 10 points

    Hi,Tiger,

    There is some confusion about the behavior of disabled PTM.From the second waveform,it didn't entry buck-boost mode immediately,but the adapter cut-off a few time,then the switch node active.Therefore,what is the condition of the swtich node active？

    Regards，

    Wang JL

  • 0 in reply to ?? ?
    TI__Mastermind 32965 points

    In the transition to the switch node active, it is also called buck-boost mode. In buck-boost mode, it is regulated to system voltage in Figure 2. 

  • 0 in reply to Tiger Zhou
    Prodigy 10 points

    Whether the system voltage is related to the current battery voltage?What's the relationship?

  • 0 in reply to ?? ?
    TI__Mastermind 32965 points

    In the NVDC architecture, the VSYS=VBAT+0.16V. 

  • 0 in reply to Tiger Zhou
    Prodigy 10 points

    Ok,thanks