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Kai Klaas
02/20/06 07:19
Read: 508 times
Germany


 
#110335 - Weak and very weak pull-ups
Responding to: Suresh R's previous message
Suresh said:
How could i know about the current and voltage being delivered by that weak pullup (pFET2).

The internal active pull-ups are current sources. Their current depends on the potential you force at port pin by an external driver.
The weak pull-up (PMOS-FET3) delivers up to 650ľA - 50ľA = 600ľA in your example. Up to 50ľA is delivered by the very weak pull-up (PMOS-FET2).

Suresh said:
Also, if i need to bring it low with an external device (a switch), i think i dont need to worry about this transition current and voltage.

Exactly, as Jan already mentioned.

Kai

List of 19 messages in thread
TopicAuthorDate
AT89s52 Port pin clarifications:      Suresh R      02/16/06 02:14      
   nice copy, where is the question      Erik Malund      02/16/06 06:30      
   output characteristics      Jan Waclawek      02/16/06 06:53      
      most confusing post      Jez Smith      02/16/06 07:34      
   Answers      Kai Klaas      02/16/06 10:35      
      Logic 1 to 0 transition      Suresh R      02/17/06 05:01      
         You haven't read the 'bible' chapter...      Kai Klaas      02/17/06 08:38      
            no details about transition from logic 1      Suresh R      02/18/06 03:27      
               other way 'round      Jan Waclawek      02/18/06 04:21      
               There ARE!!      Kai Klaas      02/18/06 06:54      
                  pFET2      Suresh R      02/19/06 07:29      
                     Weak and very weak pull-ups      Kai Klaas      02/20/06 07:19      
      maintaining low source impedence?      Suresh R      02/20/06 03:39      
         by making thje driver a sink............      Abhishek Singh      02/21/06 10:02      
         Pull-downs create problems      Kai Klaas      02/22/06 08:00      
            Maximum IOL per port pin: 10 mA ?      Suresh R      02/23/06 04:43      
               IOL      Kai Klaas      02/23/06 06:22      
                  IOL = 10mA or 1.6mA? in port 1      Suresh R      02/23/06 22:26      
                     Depends on load      Kai Klaas      02/25/06 07:40      

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