I am using this IC - LIN Mini system basis chip - TJA1128

Using the LDO in that IC to generate 3.3V with 50mA of load current. I see that the maximum output current capability of the IC is 85mA.

But where to find the data on what will the maximum current during short circuit conditions?

Is it on the page 26 table - Io(sc) - Short-circuit output current = -200mA to -85mA. (If this is it then why have they indicated with the negative sign?)

I tried to short my 3.3V to ground for a brief 150ms, I get around 180mA (measured using scope with a current probe).

Shorting just by tapping the wires and doing it manually.

My questions :

  1. Where to find the data regarding the maximum LDO short circuit output current? Is it the one which I have mentioned. If so, why have the given in negative figures?
  2. How does the IC limit the current to only that much? What is the internal mechanism?

1 Answer 1


1) You already found the max short circuit current. The footnote in the datasheet clearly says that negative currents mean current out from the chip.

2) It may be limited for safety and heat dissipation reasons so that during short circuit the regulator does not overheat and get damaged, but also so that the short circuit external to the chip does not melt wires or anything. So basically it may not need extra short circuit protection. How the chip does the limit internally is not mentioned in the datasheet, it is not important how it does it. It can use many ways depending on the regulator topology.

  • \$\begingroup\$ Just a small query. Do the short circuit current value change regardless of how long I short the voltage rail to ground? \$\endgroup\$
    – user220456
    Mar 19, 2020 at 10:46

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