• State
  • Locked Locked
  • Replies 8 replies
  • Subscribers 64 subscribers
  • Views 154 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

TPS61094: No Charge

TPS61094: Does not charge

Andris Igaunis
Prodigy 10 points
Part Number: TPS61094


Tool/software:

Dear Sir or Madam, 

I have the same issue as another person in this forum - my implementation of TPS61094 sometimes does not charge the supercap. Significantly, it often stops at ~0.7V and would not go higher. 

My setup:

Vin = 3.3V from solar panel

Vout = 3.3V

Vchg = 2.6V

Ichg = 350mA

EN = MODE = HIGH through diodes from Vin and Vout. 

I have absolutely verified that V_solar = 6.5V, Vin = 3.34V, Vout = 3.34V, EN = Mode = 3.28V, Vsupercap = 0.799V, and there is no charging for many minutes, without any sign that it would resume. Even if I unplug Solar panel, essentially making Vin = 0, and re-plugging. Also, I have put 3mF electrolytic capacitors in parallel with solar, and with Vin, and it worked better, but at a load transient of 100mA on output, the TPS61094 hang again, and stopped charging, and could not be re-forced into buck mode even with Vin = 0. It was again when Vsupercap = ~0.7V. 

Can you please check out what is going on, and if such unstable operation is to be expected? 

Best regards, 
Andris Igaunis

  • 0
    TI__Guru 67555 points

    Hello Andris,

    The supercap value is 200F. Is this correct? I am not an expert for this device (the expert is out on public holiday until next week). Let me try to help debug.

    Did you observe the same issue if you keep the 3mF connected and reduce the supercap to 50F?

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    Prodigy 10 points

    I removed 1 supercap to access components, so now it was 150F. Yes, capacitance is large (200F usually) to survive 24h. 

    Right now it is evening here, so I will continue tests tomorrow. But we designed v1 of this device 1 year ago, and from wall power supply it always worked. It seems like the device cannot handle weak source or something. It seems like if this TPS61094 senses a weak input, it does not charge supercap, and does not recover. But that is just my guess. I have a rather large charging current of 350mA, because at direct sunlight the solar panel produces plenty of energy. But of course at dim light it is not that powerful. 

    Andris

  • 0 in reply to Andris Igaunis
    TI__Guru 67555 points

    Hello Andris,

    It might be an impedance matching problem on the input side, but please expect a better help end of next week from the expert.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    TI__Genius 9325 points

    Hi Andris,

    TPS61094 enters charger mode when VOUT is 100mV higher than target. So please select 3.2V Vout to ensure it enters charger mode.

    Best Regards,

    Travis

  • 0 in reply to Travis Wang
    Prodigy 10 points

    Hello! 

    Just to clarify - my resistor settings already set Vout_target = 3.00V. And my issue is that even with actual measured Vin = Vout = 3.3V (bypass in auto mode), and target=3.0V, it still did not charge. 

    Currently I have developed a workaround where I put 3.3mF alu-el capacitor before TPS61094 (and another 3.3mF in parallel with solar panel), and the problem occured much less frequently, but still sometimes. So I developed a second workaround where my MCU also controls EN+MODE pin, and keeps it HIGH all the time, except every 1 minute it pulls those both pins LOW for 10ms, and then back high, and this resets the TPS61094 and device resumes charging even it had hanged. Care must be taken though, because LOW = Bypass mode, High = Auto mode, so MCU would shut the system off if it reset TPS61094 when solar power was absent due to night time. So MCU measures supply voltage, and if it is < 3.2V, then it skips resetting TPS61094 because it would mean that solar power is not available and TPS61094 is generating 3.0V from supercap in boost mode. 

    Best regards

    Andris Igaunis

  • 0 in reply to Andris Igaunis
    TI__Prodigy 395 points

    Hi Andris:

    When charging the super cap from 0V to 0.6V (SUP UVLO typ), it is important to ensure that the input source does not fall below 1.7 V(VIN UVLO) by drawing a high charging current or high impedance of the solar panel. If this happens, the device may stop charging. If this happens, it is recommended that you use EN=0; MODE=1 to put the device into true shutdown mode and reset it.

    Once the super cap voltage is higher than 0.85 V(SUP UVLO rising), a fall in Vin pin is not a concern any more.

    thanks. 

  • 0 in reply to Eric Jia
    Prodigy 10 points

    It would be a good recommendation, except in that case my MCU would kill its own power supply :D So as I mentioned before, I am putting it in Bypass mode (EN=0, MODE=0), and it still successfully resets charger (at least that seems to be my observation), without disconnecting VOUT from power. But thanks for the input, my observation was similar. 

    Andris

  • 0 in reply to Andris Igaunis
    TI__Genius 17990 points

    Hi Andris,

    I will follow this thread. Pls give me some time to check before questions. I will give you feedback later. Thanks for your patience.

    Aurora