Difference between revisions of "VGAX49"

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* 330 Ohm series resistor into a 75 Ohm load is 8.15 mA
 
* 330 Ohm series resistor into a 75 Ohm load is 8.15 mA
 
** Voltage with 330/75 ohm voltage divider is 0.61V - not full brightness
 
** Voltage with 330/75 ohm voltage divider is 0.61V - not full brightness
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 +
[[File:VGA_Sim_2R_Current_6_res.PNG]]
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[[File:VGA_Sim_2R_Voltage_6_res.PNG]]
  
 
== Schematic ==
 
== Schematic ==

Revision as of 10:25, 13 February 2020

VGAX49 P901-cropped-720px.jpg

Features

  • Digital VGA adapter
  • 16-bit digital video
    • 5:6:5 (R:G:B) mapping (maximum)
    • 2:2:2 (R:G:B) mapping (option)
  • Uses summing resistors
  • DB-15F connector
  • 49x49mm ODAS form factor
  • Mounting holes

Connectors

VGAX49.PNG

J1 - Digital Connections

P1 - VGA connector

Simulation

2:2:2 Resistor Simulation

  • 3.3V Drive out of FPGA
  • 1V is drive level for VGA specification
  • 8 mA max drive current
  • VGA presents a 75 Ohm load
  • Series resistors present a voltage divider between the resistors on the card and the VGA load
  • 1V at 75 Ohms is 13.3 mA
  • Each color is independently driven
  • The resistor with the smallest resistance value has larger current from the FPGA pin
  • Current switches from source to sink depending on the voltages on the other resistors
  • Use common value, 1% resistors
  • 330 Ohm series resistor into a 75 Ohm load is 8.15 mA
    • Voltage with 330/75 ohm voltage divider is 0.61V - not full brightness
  • Each resistor is 2X the value of the previous resistor
  • Next standard value from 330 ohms is 680 ohms
    • Voltage is 0.83V - better brightness

VGA Sim 2R Current.PNG

VGA Sim 2R Voltage.PNG

5:6:5 Resistor Simulation

  • 3.3V Drive out of FPGA
  • 1V is drive level for VGA specification
  • 8 mA max drive current
  • VGA presents a 75 Ohm load
  • Series resistors present a voltage divider between the resistors on the card and the VGA load
  • 1V at 75 Ohms is 13.3 mA
  • Each color is independently driven
  • The resistor with the smallest resistance value has larger current from the FPGA pin
  • Current switches from source to sink depending on the voltages on the other resistors
  • Use common value, 1% resistors
  • 330 Ohm series resistor into a 75 Ohm load is 8.15 mA
    • Voltage with 330/75 ohm voltage divider is 0.61V - not full brightness

VGA Sim 2R Current 6 res.PNG

VGA Sim 2R Voltage 6 res.PNG

Schematic

Assembly Sheet