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Original question:

Power-Path Management for USB powered +5V bus

Power-path management for usb and adaptor +9V bus

kyrin
Prodigy 110 points
Other Parts Discussed in Thread: BQ24133, BQ25792, TPS61175, BQ25886, BQ25616, BQ24105, BQ24617

I am working on a new design for which I am sure TI has a nice specific part, however, I have not been able to find the suitable one so far. This are the summarized requirements:

  • New design is more like a power bank for an infusion pump with embedded battery, and none software .
  • The input power comes from a 5V/2A USB port or 9V/1.1A adapter power supply
  • The system bus of the design is 9V±5% ,1A.
  • We will be using a 2 -cells smart battery with PCM , provide overcharge or overdischarge protection
  • A power-path management is required , so that the system is operational for supply by external power and battery
  • The most important require is ensure system current enough for the system . So need DPM or DPPM
  • When external power or load detected , a led need be present for power status (full/near empty/empty)

 

Here is my preliminary solution

  • BQ24133 is battery manager，because It had use other production
  • TPS61175PWP， 5V TO 9V ,the boost between the BQ FET and USB port
  • TPS61175PWP, 8.4V to 9V, the boost between the battery FET and the system rail
  • INA1180 , current detect with small sense resist，the sense res is between system rail and output connector.if system current above shield value then disable the charge.
  • LED driver use some comparator control and judge by battery voltage.

 Design diagram as below:

However, I am confident that TI may have specific parts suitable for this "common" application. If so, can you suggest any specific parts? If not for the whole power-path design, maybe for a subset of it?

 

Thank you for your great support！

 

Kyrin tang

  • 0
    TI__Guru**** 167096 points

    Hi Kyrin,

    Unfortunately, TI does not have a stand alone (meaning not requiring host processor and software) buck-boost charger that can accept both 9V and 5V input to charge the battery.  Your selection of BQ24133 seems to be the best fit.

    If the you want to eliminate the front end TPS61175, you might consider the BQ25792 buck-boost charger running in default mode (with ICHG=2A).  It can accept both 5V and 9V input.  However, it is NVDC power path not direct power path like BQ24133.  Therefore, the SYS output to the secondTPS61175 will be the higher of the charger's default MINSYS voltage (7V) or the battery voltage.  

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 110 points

    Thanks for your prompt response,

     

    I have seen BQ25792 ，it support IIC and USB PD 3.0 ， maybe is too complicated

     

    As I mentioned before, I need to control charge function . I found ISET pin of BQ24133 can disable the Charging when VISET < 40mv   . I'm worried the shield voltage is too low ，if some disturb signal make ISET > 40mv , will cause error charging.

     

    So is there any other IC can solve this problem?

     

    Regards，

     

    kyrin

  • 0 in reply to Jeff F
    Prodigy 110 points

    Hi jeff，

    i had another question ，BQ25792 or  BQ25886  , both IC are NCDC topologic

    -herefore, the SYS output to the secondTPS61175 will be the higher of the charger's default MINSYS voltage (7V) or the battery voltage.

    ask：it's mean that SYS output range form 7.2V - 8.6V ,so a boost need between output and IC out?

    SYS output  max load current ？What's the conversion efficiency? because i need output shuld be 9V/1A.

    Regards,

    kyrin

  • 0 in reply to kyrin
    TI__Guru**** 167096 points

    Hi Kyrin,

    Options for standalone buck only (meaning you have to use input side TPS61175) include BQ24105 or BQ25616 with NVDC power path.  I do not think your concern about the noise on ISET pin is valid.  If you use a FET to pull that pin to ground, any noise on ISET=ground would move the entire chip ground.

    Yes, boost on output is needed with NVDC power path charger.  The battery supplements system load if the charger cannot provide the required system load current.

    BQ25886 is not an option because its max input is 6.5V.  

    Efficiency curves for BQ25792 are on datasheet page 21 figure 7-4 for VBAT=8V.  The max output current for each input voltage is the last data point for each curve. Efficiency is higher when input voltage is closer to output voltage.  

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 110 points

    Hi jeff，

    Thanks for your prompt response.

    I have understand what you mean about NVDC and standalone buck . And I will take a test about ISET pin function first. And I also found BQ24617 has CE pin ,and other function is the same as BQ24133，is it a more suitable solution?

    About efficiency ，I mean If input is 5V/2A or 9V/1.1A, SYS output need 9V/1A max when discharge battery. I saw datasheet page129,the source current rating nees to be at least 3A for buck-boost converter. As my design requirement , charge current max 450mA when system load current is slightly (maybe below 120mA).charge disable when system load current above 150mA。

    Those solution with internal power-path and buck-boost convert is suitable ?

    Regards

    kyrin

     

  • 0 in reply to kyrin
    TI__Guru**** 167096 points

    Hi Kyrin,

    BQ24617 is an option but it requires external FETs.  Your current isn't high enough to warrant the heat distribution that external FETs provide, in my opinion.

    You can estimate the input power needs by using a power balance: eff=Pout/Pin=VBATREG*ICHG/(VIN*IIN).  For example, if the charger is 93% efficiency and you have 5V input source and ICHG=2A, 0.93=8.4V*2A/(5V*IIN) -> IIN=3.61A.  So, with a 5V, 2A input source, you cannot charge at 2A.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 110 points

    Hi jeff

         merry christmas ！

         i have a test with BQ24133 ，when ISET connect  to ground , charge is disable. but state pin still indicate charge.Although it does't effect to my application 

         thanks again for your help!

         Regards

         kyrin