Hi LDO team,
I have a few questions.
First, I found the drop out section of the datasheet rather confusing. It states:
Generally speaking, the dropout voltage often refers to the voltage difference between the input and output voltage (VDO = VIN – VOUT). However, in the , VDO is defined as the VIN – VOUT voltage at the rated current (IRATED), where the main current pass-FET is fully on in the ohmic region of operation and is characterized by the classic RDS(ON) of the FET. VDO indirectly specifies a minimum input voltage above the nominal programmed output voltage at which the output voltage is expected to remain within its accuracy boundary. If the input falls below this VDO limit (VIN < VOUT + VDO), then the output voltage decreases in order to follow the input voltage. Dropout voltage is always determined by the RDS(ON) of the main pass-FET. Therefore, if the LDO operates below the rated current, then the VDO for that current scales accordingly. The RDS(ON) for the TPS7A8300 can be calculated using Equation 5:
Rds(on) = Vdo/Irated
If my application is 5.3V --> 5.0V@1.5A max, then my Rds(on) = .3V/2A = 150mOhm?
It mentions a "classic Rds(on)," is that a value you guys spec for the pass FET of this part? What does that mean exactly?
Thanks!
-Brian A.
