MAX4028EUE+ Maxim Integrated Products, MAX4028EUE+ Datasheet - Page 8

• Manufacturer Part Number: MAX4028EUE+
• Description: IC AMP VIDEO MUX 2:1 16-TSSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX4028EUE+

• Applications: 2:1 Multiplexer-Amplifier
• Number Of Circuits: 3
• -3db Bandwidth: 210MHz
• Slew Rate: 300 V/µs
• Current - Supply: 29mA
• Current - Output / Channel: 30mA
• Voltage - Supply, Single/dual (±): 4.5 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Therefore, a 6kΩ resistor will produce a 1.13V key-
clamp voltage as shown in Figure 2. The clamp voltage
(V
input is V
gain (+2V/V) + V
In order for these clamps (sync tip or key) to work proper-
ly, the input must be coupled with a 0.1µF capacitor (typ)
with low leakage (<1µA to 2µA, max). Without proper cou-
pling, the clamp voltage will change during the horizontal
line time causing the “black level” to vary, changing the
image brightness from left to right on the display. In addi-
Table 1. MAX4028 Clamp Settings for Video Formats
Triple/Quad, 2:1 Video
Multiplexer-Amplifiers with Input Clamps
Figure 2. Key-Clamp Reference Voltage vs. R
R, G, B have sync on all.
Gs, B, R have sync only on Green.
8
CLAMP
_______________________________________________________________________________________
INPUT
INPUT
INPUT
1
2
3
1
2
3
1
2
3
) is measured at the output; the voltage at the
CLAMP
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1
KEY-CLAMP REFERENCE VOLTAGE
BE
(sync tip or key clamp) divided by the
3
.
FORMAT
FORMAT
FORMAT
Cvbs1
Cvbs2
Cvbs3
5
Gs
vs. R
B
R
G’
B’
R’
R
KEYREF
KEYREF
7
(kΩ)
9
CLAMP/KEY
CLAMP/KEY
CLAMP/KEY
11
Clamp
Clamp
Clamp
Clamp
Clamp
Clamp
Clamp
KEYREF
Key
Key
13
tion to the capacitor, a low resistance (≤75Ω) is required
on the source side to return the capacitor to ground. The
clamps used here are active devices with the coupling
capacitor serving two functions; first, as a charge reser-
voir to maintain the clamp voltage, and second, as the
compensation capacitor for the clamp itself. If an input is
not used, it must be terminated to avoid causing oscilla-
tions that could couple with another input.
In general, a sync-tip clamp is used for composite video
(Cvbs), gamma-corrected primaries (R’G’B’), and the
luma signal (Y) in S-video. A key clamp is preferred for
component color difference signals (Pb and Pr), linear
primaries (RGB in PCs), and chroma (C) in S-video. The
rule is to sync tip clamp a signal if sync is present and
key clamp all others. Several examples are given in the
Clamp/Key-Clamp Settings for Video Formats section.
Tables 1 and 2 provide the clamp settings on the
MAX4028/MAX4029 to interface with various video formats.
All parts feature a low-power, high-impedance disable
mode that is activated by driving the DISABLE input
low. Placing the amplifier in disable mode reduces the
quiescent supply current and places the output imped-
ance at 2kΩ typically. Multiple devices can be paral-
leled to construct larger switch matrices by connecting
the outputs of several devices together and disabling
all but one of the paralleled amplifiers’ outputs.
Low-Power, High-Impedance Disable Mode
Clamp/Key-Clamp Settings for Video Formats
INPUT
INPUT
1
2
3
1
2
3
FORMAT
FORMAT
Cvbs
Y
C
Pb
Pr
Y
CLAMP/KEY
CLAMP/KEY
Clamp
Clamp
Clamp
Key
Key
Key