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TPS2400 Overvoltage Protection Controller

Steve W1
Prodigy 100 points
Other Parts Discussed in Thread: TPS2400

Hi,


As per appnote SLVA163, I would like to protect a 12V input but the issue I have is that my 12V input is a battery so mA's of current are critical.  Your appnote indicates using low-value resistors like 2.49Kohms which would result in high current draw.  How much could I increase the value of R1 and R2 to the point where the TPS2400 circuit would not respond quickly enough ?  R1 and R2  turn on/off  the base of a MMBT5551 transistor which in turn feeds Vin of the TPS2400.

Thanks,

-Steve

  • 0
    TI__Mastermind 42795 points

    The resistors can be sized for both the UV and OV operation as well as adequate bias current for the NPN transistor. Assuming I(VIN) = 500uA (for ~12V operation which is not specified in the DS) and a BETA = 20 for the NPN transistor the base current required is ~25uA. Choose the resistor stack to be ~10x the base current and the resistance at 12V can be ~12V / 250uA or ~48kohms (R1 = 16k and R2 = 32k).

    If the BETA is higher than a larger bias resistor set could be used.