HMP8170EVAL1 INTERSIL [Intersil Corporation], HMP8170EVAL1 Datasheet - Page 13

• Manufacturer Part Number: HMP8170EVAL1
• Description: NTSC/PAL Video Encoder
• Manufacturer: INTERSIL [Intersil Corporation]

Analog Outputs
The HMP8170 converts the video data into analog signals
using four 10-bit DACs running at the CLK2 rate. The DACs
output a current proportional to the digital data. The full scale
output current is determined by the reference voltage VREF
and an external resistor RSET. The full scale output current
is given by:
I
VREF must be chosen such that it is within the part’s
operating range; RSET must be chosen such that the
maximum output current is not exceeded.
If the VREF pin is not connected, the HMP8170 uses the
internal reference voltage. Otherwise, the applied voltage
overdrives the internal reference. If an external reference is
used, it must decoupled from any power supply noise. An
example external reference circuit is shown in the
Applications section.
The HMP8170 generates 1V
across 37.5Ω loads, corresponding to doubly terminated
75Ω lines. The encoder may also drive larger loads. The full
scale output current and load must be chosen such that the
maximum output voltage is not exceeded.
Output DAC Filtering
Since the DACs run at 2x the pixel sample rate, the sin(x)/x
rolloff of the outputs is greatly reduced, and there are fewer
high frequency artifacts in the output spectrum. This allows
using simple analog output filters. The analog output filter
should be flat to F
Example filters are shown in the Applications section.
Composite + YUV Output Mode
When analog YUV video is selected, the HMP8170 scales
the filtered YCbCr data to match the levels required by its
DACs. During the scaling, values less than 16 are clamped
to 16. The scaling factors for Cb and Cr are the same, but
the CbCr scaling factor is different from the Y scaling
factor. The encoder uses different sets of scale factors for
NTSC and PAL to accommodate their different black levels.
The analog YUV outputs have a range of 0.3-1.0V with an
optional blanking pedestal. Composite sync information
FULLSCALE
NTSC/PAL 1
NTSC/PAL 2
PIN NAME
(mA) = 3.9 * VREF (V)/RSET (kΩ)
Y
C
s
/4 and have good rejection at 3F
P-P
13
PIN #
11
15
3
7
nominal video signals
COMP. WITH Y/C
Composite
Composite
TABLE 12. OUTPUT PIN ASSIGNMENTS
Chroma
Luma
(X)
s
(EQ 1.)
/4.
HMP8170
COMP. W/ RGB
OUTPUT MODE (SCART SELECT BIT)
Composite
Composite + Y/C Output Mode
The HMP8170 provides composite with S-video output
mode. When S-video outputs are selected, the encoder
outputs the luminance, modulated chrominance, and two
copies of the composite video signals. All four outputs are
time aligned. The output pin assignments are summarized in
Table 12.
Composite + RGB Output Mode
When analog RGB video is selected, the HMP8170
transforms the filtered 8:8:8 YCbCr data into 8:8:8 RGB
data. The transform matrix uses different coefficients to
generate NTSC or PAL video levels.
The analog RGB outputs have a range of 0.3-1.0V with an
optional blanking pedestal. Composite sync information
(0.0-0.3V) may be optionally added to the green output. VBI
data is not included on the RGB outputs. The HMP8170 also
generates composite video when in RGB output mode. All
four outputs are time aligned.
The HMP8170 provides selectable pin outs for the RGB
outputs. When the SCART compatibility bit is cleared, the
analog composite video is output onto the NTSC/PAL 1 pin.
Red information is output onto the NTSC/PAL 2 pin, blue
information is output onto the C pin, and green information is
output onto the Y pin.
When the bit is set, the analog composite video is output
onto the Y pin. Red information is output onto the C pin, blue
video is output on the NTSC/PAL 2 pin, and the green signal
is output on the NTSC/PAL 1 pin. The output pin
assignments are summarized in Table 12.
(0.0-0.3V) may be optionally added to the Y output. VBI data
is included on the Y output. The HMP8170 also generates
composite video when in YUV output mode. All four outputs
are time aligned. The output pin assignments are
summarized in Table 12.
Power Down Modes
To reduce power dissipation, any of the four output DACs
may be turned off. Each DAC has an independent enable bit.
Each output may be disabled in the host control register.
Green
Blue
Red
(0)
COMP. W/ RGB
Composite
Green
Blue
Red
(1)
COMP. W/ YUV
Composite
(X)
U
V
Y