Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic 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

How to Choose a Voltage Reference

Status
Not open for further replies.

aifi

Member level 2
Joined
Mar 2, 2006
Messages
42
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
1,672
Hi all..

Just for curious, why the voltage references are always set to 1.25V,2.048V,2.5V,3V, and so on..could anyone tell me please.

thanks
 

kalyanasv

Full Member level 4
Joined
May 17, 2011
Messages
192
Helped
48
Reputation
96
Reaction score
46
Trophy points
1,308
Location
NY
Activity points
2,455
The reference voltage depends on various factors: i) Type of circuit you want to build ii) Technology node iii) Interface logic....

That having said, your reference voltage for e.g. in the case of an Op-amp circuit should be a voltage which is used as a differential, which depending on the circuit design will provide the correct output.

In the case of technology node, the reference voltage for e.g. as the node size shrinks 65nm the supply could be 1.2V so you will have to have a reference voltage according to this node.

In the case of interfacing between different logic levels you could also use a reference voltage.

Most importantly the ground is also a reference voltage.
 

checkmate

Advanced Member level 3
Joined
Feb 25, 2004
Messages
833
Helped
178
Reputation
356
Reaction score
125
Trophy points
1,323
Location
Toilet Seat
Activity points
7,815
1.24V is the "golden" number for silicon-based voltage references.
As that is the bandgap voltage for Silicon, and hence the most accurate reference you can get.
All other reference voltages are derived from the bandgap voltage.
 

leo_o2

Advanced Member level 4
Joined
Sep 3, 2004
Messages
1,324
Helped
277
Reputation
556
Reaction score
240
Trophy points
1,343
Location
China
Activity points
5,761
2.5V is about double of bandgap voltage.
In fact 0.6V is chosen for reference in many power management IC.
Sometimes, reference voltage is chosen according suitable resistor values for resistor divider.
 

kalyanasv

Full Member level 4
Joined
May 17, 2011
Messages
192
Helped
48
Reputation
96
Reaction score
46
Trophy points
1,308
Location
NY
Activity points
2,455
bandgap voltages are essentially function of the technology node i.e. doping, channel length, gate width, material properties... So it is important to check it with teh technology node that the chip is designed.
 

dick_freebird

Advanced Member level 5
Joined
Mar 4, 2008
Messages
6,915
Helped
2,025
Reputation
4,054
Reaction score
1,865
Trophy points
1,393
Location
USA
Activity points
55,373
"bandgap" references have only a coincidental relation to the material
bandgap.

Aside from the 1.23-ish, the rest of the values posed are just fitted to
applications - 2.048 for a mV/LSB nice round number on an A/D, logic
family nominal VCC/VDD, low enough reference that any presently existing
logic supply output can be made by a feedback divider, etc. Somebody
wanted it, somebody built it. Not much more to it than that.
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top