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BQ25505: VSTOR output drop issue

Yoshwa
Expert 4050 points
Part Number: BQ25505
Other Parts Discussed in Thread: TMP102

Our customer sent us VSTOR output drop issue, as follows,

“At 80 degrees C (175 F) and above the VSTOR output drops from 4.2 to 2.8 volts for about 2 seconds and then recovers.”

 

What kinds of problems are considered and what kinds of detailed information should be got to fix them?

I will appreciate your help.

  • 0
    TI__Genius 12485 points
    Yoshwa-san,

    What is the temperature of the device itself if ambient is 80C? The components vary at 80C, capactiance and inductance are not the same values when they are under temperature.

    Are they using a DC voltage supply as input? What is the behavior of the harvesting element at 80C?

    regards,
    Gautham
  • 0 in reply to Gautham
    TI__Expert 4050 points

    Many thanks for your reply.

    The issue details are as follows,

    During temperature testing of the BQ25505 at temperatures >= 80 degrees C ( 176 F) the output from VSTOR shows a drop from 4.2V down to 2.8 volts and then recovers.

    Outline of the operation of the circuit

    OPT1 is a PIN diode and is supplied with 1310nm laser light in CW mode at power ranging from 0.5mW to 5mW

    depending on the losses in the fibre and distance from the source.

    This applied to the BQ25505 device in an application based on the circuit from the SLUUAA8A–September 2013–

    Revised August 2014 page 4.

    The 4.2 volt ouput is then drop via low quiescent current voltage regualtor to 2.8 volts and this supplies an ATTiny2A

    MCU which controls a TMP102 temperature sensor and a DICON MEMS switch , which is acting as an optical mirror.

    The MCU sends the temperature reading in a serial data format that drives the optical switch.

    Measured waveforms are attached.

    May I send you directly other schematics and PCB layout data?

    BQ2505_Temperature_Sensor-1.pdf

  • 0 in reply to Yoshwa
    TI__Genius 12485 points
    Yoshwa-san,

    I will contact you on email to continue this discussion. thanks,

    Gautham