Other Parts Discussed in Thread: TPS74401
For the LDO dropout, we can find the Max dropout spec from datasheet.
The max dropout spec is different according to actual load current. I have a question about the LDO Vin dropout calculation. For our actual design which is shown as follow:
Vin=5.5V±3%， Vout=4.984±3.92% （the accuracy of output is calculated according to IC, external resistor accuracy）Imax of load =0.75A;
So the min Vin dropout of our design should meet: Vin dropout>350mV according to datasheet. But I have a question about the Vin dropout calculation. Please see the following calculation method:
Cal Method 1: Vin dropout=Vin(Typ)-Vout(Typ)=5.5-4.984=516mV>350mV;
Cal Method 2: Vin dropout=Vin(Typ)-Vout(Max)=5.5-5.18=320mV<350mV;
Cal Method 3: Vin dropout=Vin(Min)-Vout(Typ)=5.5*(1-3%)-4.984=351mV>350mV;
Cal Method 4: Vin dropout=Vin(Min)-Vout(Max)=5.5*(1-3%)-4.984*(1+3.92%)=155mV<350mV;
Please help to confirm which cal method is true because it is really important for our circuit design. Thanks a lot!