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TPS3809-Q1: TPS3809I50-Q1 against BD49E50/ROHM

hideyuki sakai
Mastermind 6250 points
Part Number: TPS3809-Q1
Other Parts Discussed in Thread: TPS3809

Dear, Sir.

My customer is using BD49E50/ROHM for voltage detection. The input is provided from

resistor devider network.

They are facing a kind of Oscillation issue by this device on the system.

The symptom has been described on ROHM's datasheet, but real cause is unknown.

I would like to introduce TPS3809I50-Q1 if similar issue never ocurred using it.

Please give your advice.

1. Is there a probability similar oscillation issue as BD49E50 is occurred on TPS3809?

2. What is the possible cause inside of BD49E50 to be shown such symptom?

BD49E50.pdf

Best Regards,

H. Sakai

  • 0
    TI__Genius 12630 points
    H. Sakai,

    TPS3809 is a good option. This device can directly replace the BD49E50.

    1. TPS3809 doesn't have oscillation issues that I am aware of. I haven't heard of that issue with this device.
    2. My guess is a bad internal reference/internal comparator design without proper built in hysteresis that should be designed to prevent any oscillations or false triggers.

    Please let me know how else we can support. Thanks.
  • 0 in reply to Michael_DeSando
    Mastermind 6250 points

    Dear, Michael-san. 

    Thank you so much for your advice. 

    As I wrote on the previous mail, the customer is considering to provide VDD

    for TPS3809I50-Q1 from resistor divider. 

    I think the impact on node A, also B voltage would be huge if R1+R2 value closing to R4. 

    Please let me know the approximate resistor values if you know. 

    Best Regards, 

    H. Sakai

  • 0 in reply to hideyuki sakai
    TI__Genius 12630 points
    H. Sakai,

    The resistor values are not provided but they can be approximated. Using the supply current from Table 7.5, at 6V the supply current is 20uA. Assuming no leakage current into the internal comparator, R1 = (6V - 1.137V) / 20uA = about 240kohm. R2 = 1.137V / 20uA = about 57kohm.

    -Michael
  • 0 in reply to Michael_DeSando
    Mastermind 6250 points

    Dear, Michael-san. 

    Thank you so much for your valuable advice. 

    I tried to consider about R1=240kOHM & R2=57kOHM. 

    There is a large error on the threshold voltage & reference voltage referring this ratio. 

    I suppose  IDD error was caused by power dissipation increase on reference voltage block. 

    The lower VDD could be reduced similar error. 

    How do you think?

    Best Regards, 

    H. Sakai

  • 0 in reply to hideyuki sakai
    TI__Genius 12630 points

    H. Sakai,

    There will be less error at lower Vdd and also less error closer to room temperature. Across all input voltage and temperature, the device threshold accuracy is 2.2%.

    -Michael