AD9847AKST データシートの表示（PDF） - Analog Devices
部品番号
コンポーネント説明
メーカー
AD9847AKST Datasheet PDF : 28 Pages
| |||
AD9847
VD
HD
SHP/SHD
6
COLOR
STEERING
CONTROL
2
4:1
MUX
3 PxGA STEERING CONTROL
MODE
REGISTER
SELECTION BITS D0–D2
GAIN0
GAIN1
GAIN2
GAIN3
PxGA GAIN
REGISTERS
CDS
PxGA
VGA
Figure 17. PxGA Block Diagram
CCD: PROGRESSIVE BAYER MOSAIC SEPARATE COLOR
STEERING MODE
R
Gr
R
Gr LINE0
GAIN0, GAIN1, GAIN0, GAIN1...
Gb
B
Gb
B LINE1
GAIN2, GAIN3, GAIN2, GAIN3...
R
Gr
R
Gr LINE2
GAIN0, GAIN1, GAIN0, GAIN1...
Gb
B
Gb
B
Figure 18a. CCD Color Filter Example: Progressive Scan
CCD: INTERLACED BAYER VD SELECTED COLOR
EVEN FIELD
STEERING MODE
R
Gr
R
Gr LINE0
GAIN0, GAIN1, GAIN0, GAIN1...
R
Gr
R
Gr LINE1
GAIN0, GAIN1, GAIN0, GAIN1...
R
Gr
R
Gr LINE2
GAIN0, GAIN1, GAIN0, GAIN1...
R
Gr
R
Gr
10
8
6
4
2
0
–2
32 40
(100000)
48 58
0
8
16
PxGA GAIN REGISTER CODE
24 31
(011111)
Figure 19. PxGA Gain Curve
Variable Gain Amplifier
The VGA stage provides a gain range of 2 dB to 36 dB, program-
mable with 10-bit resolution through the serial digital interface.
Combined with 4 dB from the PxGA stage, the total gain range
for the AD9847 is 6 dB to 40 dB. The minimum gain of 6 dB is
needed to match a 1 V input signal with the ADC full-scale
range of 2 V. When compared to 1 V full-scale systems (such as
ADI’s AD9803), the equivalent gain range is 0 dB to 34 dB.
The VGA gain curve is divided into two separate regions. When
the VGA gain register code is between 0 and 511, the curve follows
a (1 + x)/(1 – x) shape, which is similar to a linear-in-dB character-
istic. From code 512 to code 1023, the curve follows a linear-in-dB
shape. The exact VGA gain can be calculated for any gain register
value by using the following two equations:
Code Range Gain Equation (dB)
0–511
512–1023
Gain = 20 log10 ([658 ϩ code] / [658 – code]) – 0.4
Gain = (0.0354)(code) – 0.04
ODD FIELD
Gb
B
Gb
B LINE0
GAIN2, GAIN3, GAIN2, GAIN3...
Gb
B
Gb
B LINE1
GAIN2, GAIN3, GAIN2, GAIN3...
Gb
B
Gb
B LINE2
GAIN2, GAIN3, GAIN2, GAIN3...
Gb
B
Gb
B
Figure 18b. CCD Color Filter Example: Interlaced
The same Bayer pattern can also be interlaced, and the VD selected
mode should be used with this type of CCD (see Figure 18b).
The color steering performs the proper multiplexing of the R, G,
and B gain values (loaded into the PxGA gain registers) and is
synchronized by the user with vertical (VD) and horizontal (HD)
sync pulses. For more detailed information, see the PxGA Timing
section. The PxGA gain for each of the four channels varies from
–2 dB to +10 dB, controlled in 64 steps through the serial inter-
face. The PxGA gain curve is shown in Figure 19.
36
30
24
18
12
6
0
0
127 255 383 511 639 767 895 1023
VGA GAIN REGISTER CODE
Figure 20. VGA Gain Curve (Gain from PxGA Not Included)
–24–
REV. A
Share Link: 