LD6143 View Datasheet(PDF) - Unspecified
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LD6143 Datasheet PDF : 9 Pages
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LD6143
Three Channel 4th Order Video Filter Driver
APPLICATION INFORMATION
Application Circuit
The LD6143 Video Filter provides 6dB gain from input to output. In addition, the input will be
slightly offset to optimize the output driver performance. The offset is held to the minimum
required value to decrease the standing DC current into the load. Typical voltage levels are
shown in the Figure 1.
There will be a 280mV offset from the DC input level to the DC output level. VOUT=2VIN+ 280mV
Figure 1. Typical voltage level
The LD6143 provides an internal diode clamp to support AC coupled input signals. If the input
signal does not go below ground, the input clamp will not operate. This allows DAC outputs to
directly drive the LD6143 without an AC coupling capacitor. When the input is AC-coupled, the
diode clamp will set the sync tip (or lowest voltage) just below ground. The worstcase sync tip
compression due to the clamp will not exceed 7mV. The input level set by the clamp combined
with the internal DC offset will keep the output within its acceptable range.
For symmetric signals like Chroma, U, V, Pb and Pr, the average DC bias is fairly constant and
the inputs can be AC-coupled with the addition of a pull-up resistor to set the DC input voltage.
DAC outputs can also drive these same signals without the AC coupling capacitor. A conceptual
illustration of the input clamp circuit is shown Figure 2.
SWID Integrated Products, 5.F, Building B, Information & Technology Park, Economic & Technological 4
Development Zone, Chong qing, China.
Tel: (86 23)62836174
Fax: (86 23)62836149
E-mail: market@swid.com.cn
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