Keep and force currents - what would be the usage? - Page 1
Forum section: electronics / beginners

author: farsi
author_rank: Regular Contributor
timestamp: August 04, 2014, 08:31:26 am
content: Hi,I got a request to measure the keep and force currents of digital pins of a device. From googling, I can't make too much sense of these concepts, except that maybe measure the current when a pin flips from low-to-high, or high-to-low.So, since my last question resulted into a really helpful discussion, it would be helpful to hear if someone here has used the concept of keep/force currents, and what the context behind this is? Also, how would you measure these parameters?Thanks!

author: sunnyhighway
author_rank: Frequent Contributor
timestamp: August 04, 2014, 12:06:55 pm
content: The force current is the current required to override the pull device with the opposite logic level.The keep current is the load current at which the pull device still maintains the valid logic level.The pull device could be a pull-up or pull-down resistor.

author: alanb
author_rank: Frequent Contributor
timestamp: August 04, 2014, 02:12:39 pm
content: I think that this terminology is from electro-mechanical relays where the current required to close the contacts (Force) is greater than the current required to keep them closed (Keep).

author: retrolefty
author_rank: Super Contributor
timestamp: August 04, 2014, 02:24:12 pm
content: Quote from: alanb on August 04, 2014, 02:12:39 pmEven then for relays the terms "pull-in" minimum current and "maintain" minimum current is more often used.I've never read of the terms 'force' and 'keep' used in any context I can recall. Might be a language translation thing?

author: David Hess
author_rank: Super Contributor
timestamp: August 04, 2014, 03:08:22 pm
content: They seem like specification that would be associated with a bus-hold function.http://en.wikipedia.org/wiki/Bus-holder

author: alanb
author_rank: Frequent Contributor
timestamp: August 04, 2014, 03:28:09 pm
content: Quote from: farsi on August 04, 2014, 08:31:26 amFarsi - are you able to supply any details of the device that you are measuring? From that we may be able to see which of the answers if any is the best fit to your question.

author: sunnyhighway
author_rank: Frequent Contributor
timestamp: August 04, 2014, 03:32:45 pm
content: Quote from: retrolefty on August 04, 2014, 02:24:12 pmInfineon seems to use these terms often. Could be a German --> English translation thing.https://www.google.nl/?gfe_rd=cr&ei=S6ffU7vFNouf-wai4YDYAw#q=%22force+current%22+%22keep+current%22+Infineon

author: farsi
author_rank: Regular Contributor
timestamp: August 04, 2014, 04:19:32 pm
content: Yes, the context is driving 0 and 1 on a bus.This might clarify the setup, a driver stage left, and some load right. The output levels are influenced by the output resistance, and by the strength of the driver left. I think, what I must check is about the maximum load that the inverter can drive.5V -----o --o----| ||-- ||--O| | || |-- | || | | || | |--- o----------------o| || || |--|---||--||GND ----o----------------------

author: farsi
author_rank: Regular Contributor
timestamp: August 04, 2014, 04:22:23 pm
content: So, can anything be concluded about the driver, when I would apply different loads/levels on the output?If this is a translation issue, what could be the proper name of the concept of keeping logical levels?