# 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 18:25, 13 February 2020

## Contents

## 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

### 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

### 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