Take TI's TPS71533 as an example. Wat does it mean by Low 3.2-µA Quiescent Current at 50 mA? Also, it only mentions the 24-V Maximum Input Voltage but no maximum input current. So wat happen if i pump in, say 15V@3A? Would it blow?
Sorry if i m asking silly question but i just dont know.
data from https://focus.ti.com/docs/prod/folders/print/tps71533-q1.html
Iout(Max)(A) 0.05
Iq(Typ)(mA) 0.0032
Obviosly you can draw current up to 50 mA
"What does it mean by Low 3.2-mA Quiescent Current at 50 mA?"
Actual 3.2 uA it meant if yor load consume current 50 mA, input current = 50mA+3.2uA , It can say ground pin current = 3.2 uA
data from h**p://focus.ti.com/docs/prod/folders/print/tps71533-q1.html
Iout(Max)(A) 0.05
Iq(Typ)(mA) 0.0032
Obviosly you can draw current up to 50 mA
"What does it mean by Low 3.2-mA Quiescent Current at 50 mA?"
Actual 3.2 uA it meant if yor load consume current 50 mA, input current = 50mA+3.2uA , It can say ground pin current = 3.2 uA
In tat case, if I got no choice but to feed in 15V@3A, can I use a resistor to limit the current so that the current supplied to this LDO does not exceed 50mA? Would 300Ω resistor enough? 15V/50mA = 300Ω
How much power is feed to the device is not the problem. You can have 24V at 10 amps availible to feed the device without any problem. When you try and pull more then 50 ma through the device it will either smoke or go into a fold back condition and self limit the current. You should not need to add any limit resitor. If you need or want to add some protection to the circuit maybe you could place a PTC (Positive thermal coefficient) device in the circuit to limit the possible current flow. It acts like a fuse but will rest when the over current condition goes away.
How much power is feed to the device is not the problem. You can have 24V at 10 amps availible to feed the device without any problem. When you try and pull more then 50 ma through the device it will either smoke or go into a fold back condition and self limit the current. You should not need to add any limit resitor. If you need or want to add some protection to the circuit maybe you could place a PTC (Positive thermal coefficient) device in the circuit to limit the possible current flow. It acts like a fuse but will rest when the over current condition goes away.
One more question is: if i want to prevent my LDO (or even a transistor) from burning due to over current supply, wat should i do? Should i use the PTC? Isnt the PTC being used like a fuse, which is normally placed at the beginning point from the DC/DC poweri supply or linear regulator?
Sorry for the long delay in response been busy here. Yes, the PTC is used as a resetable fuse. That was their original design purpose. They tend to be used in low power application. Once you get into amp and not milliamps then fuses tend to return. Many devices can be protected by fuses but it is not a common practice to add them all over a design. Most design engineers make the circuits to be self protective or just trust in the component manufactuers specification. At some point you have to trust something. Good luck.