Re: Pull up resistor
From: PeteS (ps_at_fleetwoodmobile.com)
Date: 03/12/05
- Next message: Roger Johansson: "Re: Oscilliscope and Ground"
- Previous message: PeteS: "Re: Microchip's _MCLR pull-up cct"
- In reply to: Chris W: "Pull up resistor"
- Messages sorted by: [ date ] [ thread ]
Date: 12 Mar 2005 04:22:22 -0800
One thing to watch out for is when the pullup is on a bus (such as I2C
/ SMBus). The devices used for this have a section devoted to
calculating the pullup resistance required (it's dependent on the
number of devices attached, but that's always true).
For pulling up a single pin, I agree on the 4k7 / 10k rule. If you have
to pullup / down a tri-stateable bus, then bus speed becomes a major
issue. Slow busses can be pulled with 100k or so, but fast ones ( <
25MHz or so) need more of the order of 4k7.
If they are faster than that, you may need to look at proper
terminations.
Cheers
PeteS
- Next message: Roger Johansson: "Re: Oscilliscope and Ground"
- Previous message: PeteS: "Re: Microchip's _MCLR pull-up cct"
- In reply to: Chris W: "Pull up resistor"
- Messages sorted by: [ date ] [ thread ]
Relevant Pages
|
