LP5907 – About short circuit current limit

 Q1) Could you please let us know the kind of the short circuit current limit type?

A1) Not sure I understand exactly what you asking for. This is a current limiting circuit, it allows only a certain amout of output current and does not allow the output current to exceed that level. This is intended as a functional protection circuit, outside the ensured operating range. The current limiting is not a precision circuit.

Q2 ) Could you please send us it, if you have “Isc vs Vout graph ”?

A2) Sorry, there is no such chart for LP5907.

Q3) they would like to know the drop voltage of Vout at Iout=300mA.

A3) There is no Vdo (i.e. dropout voltage) specification at Iout= 300mA. You can speculate as to what it might be by using the max ensured Vdo limit and exptrapolate out to 300mA. I presume that this is for the X2SON package, so that would be 250mV(max) at Iout=250mA. This indicates that Rds(on) = 1 ohm, so at Iout=300mA the max Vdo could be 300mV. However, there is no assurance that the LP5907 will actually perform in this manner.

Hi Donald-san,

Thank you for your response.

And I’m sorry not to have explained properly.

Please let me ask the additional question.

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Q1)

They hope that the output voltage don't stop when the current limit is operating.

However, they are supposing that the current limit operate at Iout=300mA.

Therefore, they would like to know whether the short circuit current limit type of LP5907 is "the dropping voltage type" or "the fold back limiting" or "other type"

And they would like to know whether the behavior after the current limit start is “latch” or “automatic recovery”.

Could you please let us know it?

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Q2)

I understood that you have not the graph.

Thank you for confirming.

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Q3)

Thank you for the information.

However, we would like to know not the dropout voltage(Vdo) but the drop of Vout when the current limit is operating.

(Therefore, I confirmed whether you have or not “Isc vs Vout graph ”.)

Could you please let me us it?

I guess that the output voltage is decreased by the current limit.

Because, the following comment is mentioned in the page4 of datasheet.

>Short circuit current (ISC) for the LP5907 is equivalent to current limit. To minimize thermal effects during testing, ISC is measured with

>VOUT pulled to 100 mV below its nominal voltage.

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Regards,

Kanemaru

1) the dropping voltage type

2) automatic recovery

3)  " ... but the drop of Vout when the current limit is operating ...." That is variable and depends entirely on what the situation (load) is on the output pin is. The available current is fixed and the load impedance will determine what voltage appears on the output pin.

    If the load is 1 ohm, then output current will be at Isc limit and the output voltage will be Isc x 1 ohm

    If the load is 2 ohm, then output current will be at Isc limit and the output voltage will be Isc x 2 ohm

"... VOUT pulled to 100 mV below its nominal voltage ..." Yes, that is the test condition. The output is loaded until Vout falls by 100mV. We test the output load current required to pull the output down to 100mV, This way Vin-Vout is 600mV. If we tested the output load current required to pull the output down to 0V, device dissipation would be excessive ( (Pdiss= (Vin-Vout)xIsc) ) and the part will go into thernal shutdown before we can complete the test.