HMP8156 Просмотр технического описания (PDF) - Intersil
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HMP8156 Datasheet PDF : 33 Pages
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HMP8156
External Reference Voltage
If an external reference voltage is used, its circuitry should
receive power from the same plane as the HMP8156. The
external VREF must also be stable and well decoupled from
the power plane. An example VREF circuit using a band gap
reference diode is shown in Figure 32.
Analog Output Filters
The various video standards specify the freqency response
of the video signal. The HMP8156 uses 2X oversampling
DACs to simplify the reconstruction filter required. Example
post filters are shown in Figure 33. The analog output filters
should be as close as possible to the HMP8156.
VAA
6.8K
ICL8069
+ 4.7µF
0.01µF
1.235V
FIGURE 32. EXTERNAL REFERENCE VOLTAGE CIRCUIT
1.0µH
2.2µH
1.0µH
RL
75
82pF
330pF
330pF 39pF
75
FIGURE 33A. HIGH QUALITY FILTER
2.7µH
RL
75
560pF
560pF
75
FIGURE 33B. LOW COST FILTER
FIGURE 33. EXAMPLE POST-FILTER CIRCUITS
Evaluation Kits
There are two evaluation platforms available. The
HMP8156EVAL1 is a small daughter card containing the
encoder, voltage references and bypassing, analog output
filters and connectors, a BT.656 interface and connector,
and a 50 pin two row header. The header allows connecting
the pixel and control pins of the encoder into an existing sys-
tem. The analog outputs allow the encoder’s performance to
be observed and measured.
The HMP8156EVAL2 is a standard size PC add in card with
an ISA bus interface and application software. The
HMP8156EVAL2 kit is a complete system which allows dem-
onstrating all of the encoder’s operating modes. It has ana-
log video inputs for composite, S-video, and component
RGB signals. The analog signals are converted/decoded to
the digital domain and input to the encoder. The board also
provides a 3 megabyte video RAM for image capture and
display and a BT.656 connector and interface.
32
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