Difference between revisions of "Minimig Video d/a resistor ladder"
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(imported from 'Minimig Board v1.0 documentation' section) |
(equation for base d/a resistor) |
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| Line 7: | Line 7: | ||
:U = (75*3.3)/(1/(1/4000+1/2000+1/1000+1/560)+75) = 0.6917V | :U = (75*3.3)/(1/(1/4000+1/2000+1/1000+1/560)+75) = 0.6917V | ||
: | : | ||
| + | |||
| + | :Base constant = (1/8+1/4+1/2+1/1)/(1/((R_vga*U_vcc)/U_vga-R_vga)) = 522.3214 ohm | ||
| + | |||
:[http://en.wikipedia.org/wiki/Resistor wikipedia: Resistor] | :[http://en.wikipedia.org/wiki/Resistor wikipedia: Resistor] | ||
:[http://en.wikipedia.org/wiki/Preferred_number#Capacitors_and_resistors wikipedia: Preferred number] | :[http://en.wikipedia.org/wiki/Preferred_number#Capacitors_and_resistors wikipedia: Preferred number] | ||
:[http://www.digikey.com/scripts/DkSearch/dksus.dll?Cat=65538;keywords=resistor digikey: Resistors] | :[http://www.digikey.com/scripts/DkSearch/dksus.dll?Cat=65538;keywords=resistor digikey: Resistors] | ||
Revision as of 17:25, 22 August 2007
- Equations:
- Total resistance = 1/(1/4000+1/2000+1/1000+1/560)+75
- Common current through resistor ladder plus vga impedance (75 ohm) = 3.3V / 357.8282..
- Current * vga impedance = 0.6917V (specification says 0.7 p-p)
- Output voltage = 75 * (3.3/(1/(1/4000+1/2000+1/1000+1/560)+75)) = 0.6917V
- Simplification:
- U = (75*3.3)/(1/(1/4000+1/2000+1/1000+1/560)+75) = 0.6917V
- Base constant = (1/8+1/4+1/2+1/1)/(1/((R_vga*U_vcc)/U_vga-R_vga)) = 522.3214 ohm
