LP5910: How is reverse current protection achieved?

Howard Zou

Part Number: LP5910
Other Parts Discussed in Thread: TPS706

Hi,

in LP5910 datasheet.

1. I wonder -20uA means the current flow out from IN or into IN is 20uA?

2. My customer is using some competitor's device which, when input is unconnected and output connected to 3.3V source, they will observe 3.3V at input side. They don't want the output voltage appear at the input side. So they will need reverse current protection LDO, right? Or reverse voltage protection?

3. How is reverse current protection achieved?

over 5 years ago

0 Ryan Eslinger over 5 years ago

TI__Guru 55940 points

Hi Howard,

Please allow us a couple of days to look into this.

Very Respectfully,
Ryan

0 Ryan Eslinger over 5 years ago in reply to Ryan Eslinger

TI__Guru 55940 points

Hi Howard,

The 20 uA is current flowing out of the IN pin. Since this current is flowing out of the IN pin, it will slowly charge the input capacitor raising the voltage at the IN pin.

The reverse current protection circuit senses Vin and Vout. The cathode of the parasitic body diode is connected to the higher of these two potentials; therefore, if Vin > Vout the cathode of the body diode is connected to Vin but if Vout > Vin the cathode of the body diode is connected to Vout. Below is a block diagram of this function.

Very Respectfully,

Ryan

0 Howard Zou over 5 years ago in reply to Ryan Eslinger

TI__Genius 12365 points

Ryan,
so for this particular LP5910, when Vout=3.3V, Vin=Ven=0V, it may have up to 20uA to charge the input cap at IN pin and finally IN pin voltage potential will gradually rise to the same level as Vout=3.3V?

0 Ryan Eslinger over 5 years ago in reply to Howard Zou

TI__Guru 55940 points

Hi Howard,

Yes your understanding is correct. Keep in mind that since this is a weak current, any path to GND on this rail including leakage paths will help prevent the input rail from rising.

Very Respectfully,
Ryan

0 Howard Zou over 5 years ago in reply to Ryan Eslinger

TI__Genius 12365 points

Ryan,
So do we have an absolutely 0 reverse current device?

0 Ryan Eslinger over 5 years ago in reply to Howard Zou

TI__Guru 55940 points

Hi Howard,

It is unlikely to find an LDO that does not have any leakage. We have some LDOs such as TPS706 that have a typical reverse current leakage of only 10 nA; however, we do not have any that meet your application requirements and pinout.

Very Respectfully,
Ryan

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LP5910: How is reverse current protection achieved?