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TIDA-00484: work under -20 degree

Rustem Avkhadiev
Genius 3550 points
Part Number: TIDA-00484
Other Parts Discussed in Thread: HDC1010, CC1310, ENERGYTRACE

Hello!

How long TIDA-00484 was tested under -20 degree C?

I tried to produce the same device (without boost DC-DC, Timer and Switch, using CC1310 Standby-Mode only). I set transmit period to 1 second (1 send every second) and put device in freezer under -20 C. Estimated life period was 40 days (confirmed by EnergyTrace and Fluke 87V), but device died after 5 hours (used Energizer CR2032). I tried to increase bulk capacitor capacity to 230 uF  - no success. Tried to limit battery discharge current to 3 mA (using resistor after battery), disconnect HDC1010, upload simple code from example EasyLinkTx to make sure, that it's no problems in code - no success.

In room temperature - all ok.

 

  • 0
    TI__Genius 13690 points
    Hello,

    I am going to loop in a creator of this TI Design for further support. Thank you for your patience.

    Best regards,

    Matt
  • 0
    TI__Expert 8785 points

    Rustem,

    The cold temperature can negatively impact the battery life and voltage of the coin cell.  See http://data.energizer.com/pdfs/lithiumcoin_appman.pdf for more information about Energizer batteries.

    When the device died, what is the battery output voltage?  To rule out that the issue is not caused by the battery, have you tried running the -20C test using a power supply source instead of battery?

    --Christina

  • 0 in reply to clam
    Genius 3550 points
    Hello!
    I know about this limitations, that because i used TI ref. design as a starting point.
    Than device died, battery remains changed (2.5V), and device starts working than warmed to +20 with the same battery.
    I made -20C tests than device was powered by LaunchPad - all ok, estimated life period was 40 days (confirmed by EnergyTrace and Fluke 87V).
  • 0 in reply to Rustem Avkhadiev
    TI__Mastermind 25331 points

    Rustem Avkhadiev said:
    I made -20C tests than device was powered by LaunchPad - all ok, estimated life period was 40 days

    So does confirm that the battery is the cause of the problem?

  • 0 in reply to Gus Martinez
    Genius 3550 points
    I tried many different batteries with the same result. Problem is in limitations of battery power supply. My device need to be powered only by the CR2032 (as TIDA-00484). In TIDA-00484 guide i see:
    Temperature range: -30 +85
    Life time with 1 CR2032: > 10 years.
    That why i ask - how it's was archived?
  • 0 in reply to Rustem Avkhadiev
    TI__Mastermind 25331 points

    Rustem Avkhadiev said:
    That why i ask - how it's was archived?

    The design was placed inside a temperature/humidity chamber as described in section 6.4 of the design guide.  

    During your testing, are you directly measuring the current being consumed by the components in the design?  For example, if you look at the schematics for TIDA-00484, this would mean measuring the current flowing through J1.  This may help confirm whether the problem is indeed the battery or some component on the board draining too much current at low temperatures.

  • 0 in reply to Gus Martinez
    Genius 3550 points

    Hello!
    Yes, i measured current right after the battery (on J1 in TIDA-00484 terminology), it's ok, no unexpected current drain.
    As i see in design guide, board was tested on -30 C for a several minutes only. If you have assembled board of TIDA-00484, can you put it in freezer (-20 C) with CR2032 for a several days and tell me how long it will work (without removing it from freezer)?

  • 0 in reply to Rustem Avkhadiev
    TI__Mastermind 25331 points
    We may not be able to get to such a test for a while due to resource constraints. Although, even if we run the test I'm not clear how that would help you. If our test result shows reduced battery life, then we might conclude the battery is the issue, which would just confirm what you are seeing. If we don't see decreased battery life, then we still don't know what is the root cause of the issue in your design.
  • 0 in reply to Gus Martinez
    Genius 3550 points
    I need this information because i'm little bit confused, i have 2 TI documents:
    1. www.ti.com/.../swra349.pdf - says that's it impossible to run cc1310 with cr2032 under -20 C without bulk capacitor < 300 uF
    2. www.ti.com/.../TIDA-00484 - says that cc1310 with cr2032 under -20 C can run with 100 uF buck capacitor
    I need to choose direction of the way to solve this issue:
    1. Change the board size and insert additional capacitors, with additional cost and current leakage (bad way)
    2. Find error in my design to archive result with 100 uF capacitor (good way)
  • 0 in reply to Rustem Avkhadiev
    TI__Mastermind 25331 points
    At the time SWRA349 was written, the radio devices mentioned in the white paper required more bulk capacitance because they required more energy to transmit data. The CC1310 consumes less energy, therefore less capacitance is required.
  • 0 in reply to Gus Martinez
    Genius 3550 points
    Hello!
    1. How bulk capacitance value was calculated in www.ti.com/.../TIDA-00484 ?
    2. What is estimated battery life time of www.ti.com/.../TIDA-00484 then working under -20C?
  • 0 in reply to Rustem Avkhadiev
    TI__Mastermind 25331 points
    The bulk capacitance was sized taking into account the load currents measured during testing. Having said that we do need to add a note to the design guide to clarify battery life estimates were made based on room temperature conditions. As you already know, at lower temperatures the capacity of the battery will decrease or, conversely, the internal load resistance of the battery will increase. As you pointed out and as is described in SWRA349 the bulk capacitor can mitigate this issue. If you can share your calculations for arriving at the 300uF bulk cap value we can sanity check those calculations and provide additional feedback.
  • 0 in reply to Gus Martinez
    Genius 3550 points
    Hello!
    I've just used formula from page 10 of SWRA349:
    C = ( 5 ms * 25 mA (TX period) + 6 ms * 5 mA (other periods) ) / 2.6V - 2V = 258 uF.
    Taking into account -20% capacity tolerance gives 300 uF.
  • 0 in reply to Rustem Avkhadiev
    TI__Mastermind 25331 points

    I think you have the right approach, but the unknown is the actual battery voltage at the battery's end-of-life (Vmax).  I only see a plot for at 0C in the Energizer CR2032 data sheet; there is no plot for -20C.  Even a slightly lower Vmax can have a big impact on the size of the bulk cap.