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LDO with current limiting circuit

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Chethan

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current limiting circuit

Can some one explain, where the output of the current limiting circuit should be connected in an PMOS LDO. The following circuit shows that both the outputs of current limiting circuit and thermal shutdown connected to error amplifier. can some one explain how to do this ???

thanx in advance
 

current limit circuit

Have a look at the schematic below ..
The top opamp is the error amplifier; the bottom opamp is the current limit circuit ..
Outputs of both are connected together (resistor+diode) to perform OR function: voltage OR current controls the output ..
By analogy in your circuit (it can be confusing, as these signals have nothing to do with the error amplifier), the outputs from current limit and thermal shutdown will be combined somewhere with the output of the error amplifier to produce a control signal to the power MOSFET ..

Regards,
IanP
 

ldo current limit

Both of Thermal shutdown and current limit go to the op-amp internal circuitry which not shown.
but it is obvious both of 2 signal act similarly, and decrease of shutdown output voltage to zero.
 

mosfet current limit circuit

IanP said:
Have a look at the schematic below ..
The top opamp is the error amplifier; the bottom opamp is the current limit circuit ..
Outputs of both are connected together (resistor+diode) to perform OR function: voltage OR current controls the output ..
By analogy in your circuit (it can be confusing, as these signals have nothing to do with the error amplifier), the outputs from current limit and thermal shutdown will be combined somewhere with the output of the error amplifier to produce a control signal to the power MOSFET ..

Regards,
IanP
Click to expand...

could you tell me the operational principle of this circuit?so to speak,how does the current _limited amplifier to control the ciruit?
thank you
 

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