LP5910: LP5910-1.3V

Hi Zhengqing,

to work properly the input voltage should be 0.5V higher than the output voltage. So, for 1.3V output voltage 1.4V input voltage is too low.

Kai

Hi Zhengqing,

We do not currently have any plans to release a 1.3 V output. Could you help us understand your application requirements for the LDO? Perhaps we can help you select a released device that can fit your application needs.

Very Respectfully,
Ryan

So you mean Input voltage should have 0.5V higher than output which means I need at leat 1.8V for 1.3V output?

But in data sheet, it said LP5910 is a low drop LDO. The dropout: 120 mV (Typical). How about this typical value can I use this as the voltage between input and output and set current to 50mA?

Many thanks.

Hi Zhengqing,

yes, 1.8V would be necessary.

Please see the footnote (8) at page 5 of datasheet:

"(8) Dropout voltage is the voltage difference between the input and the output at which the output voltage drops to 100 mV below its nominal value. Dropout voltage is not a valid condition for output voltages less than 1.3 V as compliance with the minimum operating input voltage can not be ensured."

By other words, when the output voltage drops 100mV below its nominal value, when observing the dropout voltage, the regulator is out of regulation. It doesn't work properly. This is true for all voltage regulators. The dropout voltage is only a parameter to compare voltage regulators.

Kai

Thanks,

My situation need a low dropout voltage LDO. 1.4V input 1.3V output. Any suggestion? 

Many thanks.....

Hi Zhengqing,

It's rather unsusual to have such a small input to output differential voltage. If you take into consideration that the 1.4V and the 1.3V are usually fabricated with tolerances, then the input to output differential voltage of 100mV will furtherly decrease. Assume a 2% tolerance for each supply, then you end up with 1.4V x 0.98 = 1.372V and 1.3V x 1.02 = 1.326V. So, your differential voltage melts down to 46mV. And if you still consider noise and ripple on both supply voltages and temperature drift of output voltage, you will see that the regulator can no longer work, even if it was an ideal regulator.

So either you take another supply voltage for feeding the input of LP5910 which is >1.8V or you could use a charge pump for increasing the 1.4V to >1.8V.

Kai

Dear Kai,

Many thanks for your help.
Here is the demand:
Vin: 1.4v
Vout: 1.3v
Current: 50mA
Any suggestion for this case？

I check this via TI website, are TPS720 and LP5952 suitable for this case?

Many thansk.