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.

usage of pullup resistor

Status
Not open for further replies.

aandavan

Advanced Member level 4
Joined
Aug 31, 2006
Messages
106
Helped
8
Reputation
16
Reaction score
7
Trophy points
1,298
Location
india
Activity points
1,932
What is the use of pullup resistor and puldown resistor???????
 

IanP

Advanced Member level 5
Joined
Oct 5, 2004
Messages
7,942
Helped
2,311
Reputation
4,624
Reaction score
531
Trophy points
1,393
Location
West Coast
Activity points
66,416
Use SEARCH (between FAQ and Memberlist) and you will find more ..

Regards,
IanP
 

A.Anand Srinivasan

Advanced Member level 5
Joined
Oct 15, 2005
Messages
1,804
Helped
257
Reputation
514
Reaction score
39
Trophy points
1,328
Location
India
Activity points
10,680
pull up resistor is used to provide swing of the output till the positive supply.... pull down resistor for providing swing till the negative supply... there is a tradeoff involved between speed and power dissipation wrt the resistor value....
 

btbass

Advanced Member level 5
Joined
Jul 20, 2001
Messages
1,897
Helped
438
Reputation
880
Reaction score
287
Trophy points
1,363
Location
Oberon
Activity points
12,863
Pullups/ Pull downs are used on input lines.
An input line has to be high impedance other wise it would load the signal it is trying to monitor.
So if left open, it will float with no defined value.
It might even begin to oscillate, causing overheating and system crash.
A pullup/pulldown puts it in a well defined state, either high or low. It then needs a positive driving signal to make it change state.
IE: with a 10K pullup and a switch shorting the 10K to ground. You can then be sure if the switch is open or closed.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top