Datasheet AD8074, AD8075 (Analog Devices) - 10
| Manufacturer | Analog Devices |
| Description | 500 MHz, G=+1 and +2 Triple Video Buffers with Disable |
| Pages / Page | 15 / 10 — AD8074/AD8075. RGB Buffer for Second Monitor. MONITOR #1. PC GRAPHICS IC. … |
| Revision | B |
| File Format / Size | PDF / 768 Kb |
| Document Language | English |
AD8074/AD8075. RGB Buffer for Second Monitor. MONITOR #1. PC GRAPHICS IC. CURRENT SOURCE. OUTPUT DRIVERS. INTERNAL. TERMINATIONS. +5V
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AD8074/AD8075 RGB Buffer for Second Monitor
can be connected to the same signal, as is done in some studio- The RGB signals for PC monitors are driven through coax type TV monitors. cables whose characteristic impedance is 75 Ω. The graphics A way around this problem is to connect the first monitor to the chip will generally have current-source output drivers that should RGB channels in the standard fashion, and then to provide a be double terminated with a 75 Ω shunt termination at each end. triple gain-of-two buffer to drive the second monitor. The AD8075 On the transmit end, the shunt terminations are provided to is designed to provide this function and also provide excellent ground close to the graphics IC, while the monitor terminates high-frequency performance for high-resolution graphics signals. its end via internal termination resistors. While this scheme works Figure 3 shows a schematic of this circuit. well and is virtually foolproof for a single monitor, it leaves no The outputs of the AD8075 are low impedance voltage sources means for passively connecting a second monitor to the same source. and are therefore series-terminated with 75 Ω resistors. The A second monitor that is connected simply in parallel will pro- internal resistors in Monitor #2 provide the terminations at its vide an extra set of terminations that will upset the signal levels. end. The overall effect of this type of termination scheme is to To keep costs low, most computer monitors do not have the ability divide the signal amplitude by two. This is compensated by the to open-circuit the terminations in order that an additional monitor gain of two provided by the AD8075.
MONITOR #1 PC GRAPHICS IC R 75
⍀
75
⍀
CURRENT SOURCE G OUTPUT DRIVERS INTERNAL 75
⍀
75
⍀
TERMINATIONS B 75
⍀
75
⍀
+5V +5V +5V + 25
F 0.1
F 0.1
F 0.1
F MONITOR #2 75
⍀
75
⍀
AD8075 75
⍀
75
⍀
INTERNAL TERMINATIONS 75
⍀
75
⍀
25
F 0.1
F 0.1
F 0.1
F + –5V –5V –5V
Figure 3. Buffer –10– Rev. B Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM PRODUCT DESCRIPTION AD8074/AD8075-SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ESD CAUTION MAXIMUM POWER DISSIPATION AD8074/AD8075-TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION OUTLINE DIMENSIONS ORDERING GUIDE
AD8074/AD8075 RGB Buffer for Second Monitor
can be connected to the same signal, as is done in some studio- The RGB signals for PC monitors are driven through coax type TV monitors. cables whose characteristic impedance is 75 Ω. The graphics A way around this problem is to connect the first monitor to the chip will generally have current-source output drivers that should RGB channels in the standard fashion, and then to provide a be double terminated with a 75 Ω shunt termination at each end. triple gain-of-two buffer to drive the second monitor. The AD8075 On the transmit end, the shunt terminations are provided to is designed to provide this function and also provide excellent ground close to the graphics IC, while the monitor terminates high-frequency performance for high-resolution graphics signals. its end via internal termination resistors. While this scheme works Figure 3 shows a schematic of this circuit. well and is virtually foolproof for a single monitor, it leaves no The outputs of the AD8075 are low impedance voltage sources means for passively connecting a second monitor to the same source. and are therefore series-terminated with 75 Ω resistors. The A second monitor that is connected simply in parallel will pro- internal resistors in Monitor #2 provide the terminations at its vide an extra set of terminations that will upset the signal levels. end. The overall effect of this type of termination scheme is to To keep costs low, most computer monitors do not have the ability divide the signal amplitude by two. This is compensated by the to open-circuit the terminations in order that an additional monitor gain of two provided by the AD8075.
MONITOR #1 PC GRAPHICS IC R 75
⍀
75
⍀
CURRENT SOURCE G OUTPUT DRIVERS INTERNAL 75
⍀
75
⍀
TERMINATIONS B 75
⍀
75
⍀
+5V +5V +5V + 25
F 0.1
F 0.1
F 0.1
F MONITOR #2 75
⍀
75
⍀
AD8075 75
⍀
75
⍀
INTERNAL TERMINATIONS 75
⍀
75
⍀
25
F 0.1
F 0.1
F 0.1
F + –5V –5V –5V
Figure 3. Buffer –10– Rev. B Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAM PRODUCT DESCRIPTION AD8074/AD8075-SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ESD CAUTION MAXIMUM POWER DISSIPATION AD8074/AD8075-TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION OUTLINE DIMENSIONS ORDERING GUIDE
