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TPS65400: Questions about current measurement accuracy and data write lifetime

Carolus Andrews
Mastermind 22650 points
Part Number: TPS65400

Team,

I have a customer that wishes to know the following about TPS65400:

I received your contact from a co-worker of mine, and I was wondering if you could answer a few questions about a part that I am considering, or direct me to someone that could answer my questions. 

  1. I see that the current limit accuracy is +/-25%, which I am okay with, however this makes me question the current measurement accuracy of the chip when an output is not in current limit. Do you know the current measurement accuracy for this device during normal operation?
  1. Seeing as how this chip is a programmable device, I would like to know the data retention of the on board flash memory that holds the hard coded values for the outputs. In other words, how long will the on board memory last for after programming the device (i.e. 10 years, 20 years,…etc) ?

Do we have this information to be able to share with the customer? 

  • 0
    TI__Genius 15135 points

    Hi, Andrews

    1. The current limit circuit is detecting the voltage drop of POWER MOSFET (IL*Rdson) during on time, and compare it with reference voltage to judge whether OC happens, due to the Rdson of POWER MOSFET has big variation over temperature, so the current limit has large variation(+/-25%). 
    During normal operation, the current measurement accuracy is determined by multimeter which is in series with Vout, it has high precision.  
    2. The data is stored in Non-Volatile Memory Default Store(EEPROM), usually guarantee data retention of 10 years or more.

  • 0 in reply to Zhao Ma
    TI__Mastermind 22650 points

    Zhao,

    Do we have any data as to a numerical precision for the current sense circuit(multimeter) in line with Vout? +/-1%? +/-2% I don't see any associated specifications for this measurement in the datasheet,

    Also, are you saying I can tell the customer that we guarantee data retention of at least 10 years, but performance may be even better? If so, why do we not say that in the datasheet?

  • 0 in reply to Carolus Andrews
    TI__Genius 15135 points
    Hi, Andrews

    1. I think I misunderstood your question.
    Confirm with your question:
    You want to know the accuracy of internal current sense circuit, right? (I thought you want to know the curent accuracy in test measurement.)
    The internal current sense circuit uses the Rdson of POWER MOSFET to sample inductor current, for different parts and different temperature, the big Rdson variation will cause the sense current accuracy has big variation.
    I think whenever in current limit or normal working, the sensing current accuracy is same, equal to +/-25%.

    2. Yes, the performance may be better.
    I think the data retention of at least 10 years is the common advantage for EEPROM, not TI's unique advantage, so the datasheet not mention this advantage.
    Of course, saying this advantage in datasheet will be better.
  • 0 in reply to Zhao Ma
    TI__Mastermind 22650 points

    Zhao,

    Hope you had a great holiday, and happy new year!

    In regards to question 1, yes, the customer wishes to know the level of accuracy of the device during normal operation. For example, if the current limit of the device is set to 4 amps, but the load being drawn is only 1 amp,  what is the current measurement accuracy of the 1 amp measurement? Is it also the 25% like the current limit accuracy, or is it better/worse?

  • 0 in reply to Carolus Andrews
    TI__Genius 15135 points

    Hi, Andrews

    Happy new year!

    Have confirmed with designer, during normal operation, the current sense accuracy is almost same with the current limit accuracy.