Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

What is dropout voltage?

Status
Not open for further replies.
L

Lucifre

Full Member level 2
Full Member level 2
Joined
Jul 5, 2005
Messages
125
Helped
2
Reputation
4
Reaction score
0
Trophy points
1,296
Location
Detroit MI
Visit site
Activity points
2,389
What is drop out voltage in voltage regulators? on every datasheet they give a graph of drop out voltage versus temperature... is it the minimum difference between input and output voltages?
 

The dropout voltage is defined as the minimum voltage drop required across the
regulator to maintain output voltage regulation ..

Regards,
IanP
 
i have saw a definition: the dropout voltage is defined as the minimum voltage when the output voltage has dropped 2% while sustain fixed output current
 
Hi Lucifre,
The DropOut Voltage in Linear Regulator Voltage depends on its characteristics, for example, in Regulators LMxxx it is 2V aprox. in Reg with Low DropOut Voltage it is <1V aprox.

If you need obtain a Power Supply with linear regulators, you should to do:

VOreq + Vdor + 2 Vd = Vmin wihout ripple
where:
VOreq is Voltage output required
Vdor is DropOut Voltage on IC regulator
Vd is dropouto across diode

rgds
 

IanP said:
The dropout voltage is defined as the minimum voltage drop required across the
regulator to maintain output voltage regulation ..

Regards,
IanP
Click to expand...


could you introduce some useful books about LDO? thanks a lot!

Added after 1 minutes:

IanP said:
The dropout voltage is defined as the minimum voltage drop required across the
regulator to maintain output voltage regulation ..

Regards,
IanP
Click to expand...

could you introduce some useful books to me ? thanks a lot!
 

Dropout voltage is the input-to-ouput differential voltage at which the circuit ceases to regulate against further reductions in input voltage;this point occurs when the input voltage approaches the output voltage. The below figure shows a typical LDO regulator circuit. In the dropout region, the PMOS pass element(assume output transistor is PMOS) is simply a resistor, and dropout is expressed in terms of its on-resitance(Ron).
Vdropout=Io×Ron
 

Drop out voltage is the minimum input/output differentialvoltage where the circuit just ceases to regulate.
 

Hi

huojinsi is correct.
For simplicity, there's nothing need to remember.
Just remind yourself, when the INPUT voltage close to OUTPUT voltage such that the PASS element changes from saturation to linear region, that is, the VDS(sat), this is AROUND the drop-out voltage. What does it mean?
The name already explains its meaning.
The input/output voltage difference when output ceases to regulate itself and then it DROPS OUT of the regulation.
 

lTo: iuyonggen_1
The most useful book is Rinconmora book. You can download it from this link.



Success.
 

from the name, it is so easy to tell that is the diff of supply voltage and the output voltage. Things seem more difficult when VDD shrinks to 1.5v (+/- 10%) but you may need output 1.2v which big current output requirement
 

the minimum difference required between input and output of ldo when it is regulating is dropout voltage
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top