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TPS61325 / precharge current control

Ryuji
Guru 20090 points
Other Parts Discussed in Thread: TPS61325
Hello,
 
I would like to know about TPS61325 pre-charge function.
 
(1)
I think that pre-charge current meaning charge current from Battery to SUPER CAP.
And pre-charge current  range is 80mA ~ 220mA in the datasheet page 3.
 
Can I setting pre-charge current by register ?
 
(2)
Can TPS61325 pre-charge to SUPER CAP during Flash to Flash ?
 
For exmample,
First flash ---> 300ms ---> Second Flash.
Can TPS61325 pre-charge to SUPER CAP in this 300ms ?
 
Best Regards,
Ryuji Asaka
 
 
 
 
  • 0
    TI__Expert 7110 points

    Hi Ryuji,

    the pre-charge function implemented in the TPS61325 has the functionality to charge VOUT during start-up (see Datasheet section START-UP SEQUENCE on page 33).

    However, let me directly answer your questions:

    1. The Pre-charge current limit can not be set by register (refer above named section)
    2. The Pre-charge sequence is only executed as a part of the start-up. After that the device works as defined by your settings and application

    Kind regards,

    Florian

  • 0 in reply to Florian Feckl
    Guru 20090 points
    Hello Florian san,
     
    Thanl you for the reply.
     
    I understood that Pre-Charge current is start up charge current for avoiding inrush current due to super-capacitor.
    And Pre-charge current is larged step by step.
    So I understood that Pre-Charge is similar to Soft Start function of general DCDC converter.
     
    Please kindly confirm my understanding.
     
    (1)
    Charge current from Battery to Super-Cap is configured by Flash Current Control Bit( data sheet Page 47) in case of below condition.
    HC_SEL=0
    Flashlight mode
    Voltage mode operation
     
    If my understanding incorrect please kindly let me know the current setting from Battery to Super cap ?
     
    (2)
    If I use Flashlight mode.
    Super Cap is charged during Flash to Flash.
    Is my understanding correct ?
     
    Sorry for bothering you, but please kindly let me know.
     
    Best Regards,
    Ryuji Asaka
     
  • 0 in reply to Ryuji
    Guru 20090 points
    Hello Florian san,
     
    I'm Sorry.
    I was miss understanding.
    Please ignore above posting.
     
     
    Could you please kindly let me know the calculation of charge time with supercapacitor?
    I can't find any calculation in datasheet.
    If there is any application note, please let me know.
     
    Best Regards,
    Ryuji Asaka
     
  • 0 in reply to Ryuji
    TI__Expert 7110 points

    Hi Ryuji-san,

    I am sorry, but we don't have any Apps Note capturing this topic.

    It's not easy to help you designing your application without knowing the details. Your question depends on many parameters: Cap, Current Limit, Led Circuits, Voltage Mode Operation...

    Could you go a bit more in detail how your application works?

    Regards,

    Florian

  • 0 in reply to Florian Feckl
    Guru 20090 points
    Hello Florian san,
     
    Thank you for the checking.
    I will check more detail to my customer and let you know if we get information.
     
    Best Regards,
    Ryuji Asaka