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rajesh13
Joined: 07 Jul 2004
Posts: 126
Location: Milky Way
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 02 Aug 2004 10:12 slew control in cmos I/Os circuit |
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I want to know why & how slew contro is done (dI/dt) is done is cmos I/Os circuit. I am basically interested in active slew rate control techniques.
Last edited by rajesh13 on 10 Aug 2004 7:06; edited 1 time in total |
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yjkwon57
Joined: 31 Jul 2004
Posts: 221
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| 02 Aug 2004 14:05 Re: slew contron in cmos I/Os circuit |
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Hi rajesh
The current control of an output I/O cell is very important because of the large parasitic inductances and capacitances of the IC package and the PCB, which causes the voltage swing and affect the GND and all the circuits. In the IC package, the pad size, bonding wire, and configuration of the pins are relavant. These informations are usually provided by the packaging guys. The relavant information can be obtained from the PCB manufacturer. After obtaining all relavant information, the SPICE simulation is to be performed for the output I/O cells so as to determine the W/L of the transistors and meet the tolerance of the swing. There are many types of I/O cells already developed and used, which are organized in more than one stage for the effective control of the output currents.
Bye~~
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sunking
Joined: 25 May 2004
Posts: 914
Helped: 46
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| 03 Aug 2004 2:10 Re: slew contron in cmos I/Os circuit |
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| Yes. Many company has their own lib of I/O circuit which has be validated. They can select with the different function.
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rajesh13
Joined: 07 Jul 2004
Posts: 126
Location: Milky Way
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| 03 Aug 2004 9:54 Re: slew contron in cmos I/Os circuit |
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| sunking wrote: |
| Yes. Many company has their own lib of I/O circuit which has be validated. They can select with the different function. |
Do you know some schemes in cmos I/Os.
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modern_analog
Joined: 11 Jul 2004
Posts: 9
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| 10 Aug 2004 0:55 Re: slew contron in cmos I/Os circuit |
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generally slew control is done by
a) slowing down the pre-driver
b) splitting the transistors into multiple smaller legs and delaying one with the other by putting R in the gate.
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rajesh13
Joined: 07 Jul 2004
Posts: 126
Location: Milky Way
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| 10 Aug 2004 6:08 Re: slew contron in cmos I/Os circuit |
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| modern_analog wrote: |
generally slew control is done by
a) slowing down the pre-driver
b) splitting the transistors into multiple smaller legs and delaying one with the other by putting R in the gate. |
Do you know about some PVT compensated techniques.
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yoho
Joined: 30 Jun 2004
Posts: 90
Helped: 1
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| 18 Aug 2004 11:50 Re: slew control in cmos I/Os circuit |
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Take a look at the paper "CMOS output drivers with reduced ground bounce and EMI" by Deutschmann/Ostermann
www.chipidea.com/esscirc2003/presentations/esscirc/c30/003_559.pdf
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