AD9848AKST Просмотр технического описания (PDF) - Analog Devices
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AD9848AKST Datasheet PDF : 32 Pages
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AD9848/AD9849
Register Name
POL
POSLOC
NEGLOC
DRV
Length
1b
6b
6b
3b
Table II. H1–H4, RG, SHP, SHD Timing Parameters
Range
High/Low
0–47 Edge Location
0–47 Edge Location
0–7 Current Steps
Description
Polarity Control for H1, H3, and RG (0 = No Inversion, 1 = Inversion)
Positive Edge Location for H1, H3, and RG
Sample Location for SHP, SHD
Negative Edge Location for H1, H3, and RG
Drive Current for H1–H4 and RG Outputs (3.5 mA per Step)
Quadrant
I
II
III
IV
Table III. Precision Timing Edge Locations
Edge Location (Decimal)
0 to 11
12 to 23
24 to 35
36 to 47
Register Value (Decimal)
0 to 11
16 to 27
32 to 43
48 to 59
Register Value (Binary)
000000 to 001011
010000 to 011011
100000 to 101011
110000 to 111011
H-Driver and RG Outputs
In addition to the programmable timing positions, the AD9848/
AD9849 features on-chip output drivers for the RG and H1–H4
outputs. These drivers are powerful enough to directly drive the
CCD inputs. The H-driver current can be adjusted for optimum
rise/fall time into a particular load by using the DRV registers.
The RG drive current is adjustable using the RGDRV register.
Each 3-bit DRV register is adjustable in 3.5 mA increments, with
the minimum setting of 0 equal to OFF or three-state, and the
maximum setting of 7 equal to 24.5 mA.
As shown in Figure 7, the H2/H4 outputs are inverses of H1/H3.
The internal propagation delay resulting from the signal inversion
is less than l ns, which is significantly less than the typical rise time
driving the CCD load. This results in a H1/H2 crossover voltage
at approximately 50% of the output swing. The crossover voltage
is not programmable.
Digital Data Outputs
The AD9848/AD9849 data output phase is programmable
using the DOUTPHASE register. Any edge from 0 to 47 may
be programmed, as shown in Figure 8.
HORIZONTAL CLAMPING AND BLANKING
The AD9848/AD9849’s horizontal clamping and blanking
pulses are fully programmable to suit a variety of applications.
As with the vertical timing generation, individual sequences are
defined for each signal and are then organized into multiple
regions during image readout. This allows the dark pixel clamping
and blanking patterns to be changed at each stage of the readout
to accommodate different image transfer timing and high speed
line shifts.
H1/H3
tRISE
H2/H4
tPD << tRISE
FIXED CROSSOVER VOLTAGE
tPD
H1/H3
Figure 7. H-Clock Inverse Phase Relationship
H2/H4
P[0]
CLI
1 PIXEL PERIOD
tOD
DOUT
P[12]
P[24]
P[36]
P[48] = P[0]
NOTES
1. DIGITAL OUTPUT DATA (DOUT) PHASE IS ADJUSTABLE WITH RESPECT TO THE PIXEL PERIOD.
2. WITHIN 1 CLOCK PERIOD, THE DATA TRANSITION CAN BE PROGRAMMED TO ANY OF THE 48 LOCATIONS.
Figure 8. Digital Output Phase Adjustment
–20–
REV. A
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