AD9992 데이터 시트보기 (PDF) - Analog Devices

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AD9992

12-Bit CCD Signal Processor with Precision Timing Generator

Analog Devices 

AD9992

HIGH SPEED PRECISION TIMING CORE

The AD9992 generates high speed timing signals using the flexible

Precision Timing core. This core is the foundation for generating

timing used for both the CCD and the AFE; it includes the reset

gate RG, horizontal drivers H1 to H8, HL, and SHP/SHD sample

clocks. A unique architecture makes it routine for the system

designer to optimize image quality by providing precise control

over the horizontal CCD readout and the AFE correlated

double sampling.

The high speed timing of the AD9992 operates the same way in

either master or slave mode configuration. For more informa-

tion on synchronization and pipeline delays, see the Power-Up

Sequence for Master Mode section.

Timing Resolution

The Precision Timing core uses a 1× master clock input (CLI) as

a reference. This clock should be the same as the CCD pixel

clock frequency. Figure 15 illustrates how the internal timing

core divides the master clock period into 64 steps or edge

positions. Using a 40 MHz CLI frequency, the edge resolution of

the Precision Timing core is approximately 0.4 ns. If a 1× system

POSITION

P[0]

P[16]

clock is not available, it is possible to use a 2× reference clock by

programming the CLIDIVIDE register (AFE Register

Address 0x0D). The AD9992 then internally divides the CLI

frequency by 2.

The AD9992 includes a master clock output (CLO) which

is the inverse of CLI. This output should be used as a crystal

driver. A crystal can be placed between the CLI and CLO pins

to generate the master clock for the AD9992.

High Speed Clock Programmability

Figure 16 shows when the high speed clocks RG, H1 to H8,

SHP, and SHD are generated. The RG pulse has programmable

rising and falling edges and can be inverted using the polarity

control. Horizontal Clock H1 has programmable rising and

falling edges and polarity control. In HCLK Mode 1, H3, H5,

and H7 are equal to H1. H2, H4, H6, and H8 are always inverses

of H1.

The edge location registers are each six bits wide, allowing

selection of all 64 edge locations. Figure 19 shows the default

timing locations for all high speed clock signals.

P[32]

P[48]

P[64] = P[0]

CLI

tCLIDLY

ONE PIXEL

PERIOD

NOTES

1. THE PIXEL CLOCK PERIOD IS DIVIDED INTO 64 POSITIONS, PROVIDING FINE EDGE RESOLUTION FOR HIGH SPEED CLOCKS.

2. THERE IS A FIXED DELAY FROM THE CLI INPUT TO THE INTERNAL PIXEL PERIOD POSITION (tCLIDLY).

Figure 15. High Speed Clock Resolution from CLI, Master Clock Input

1

CCD

2

SIGNAL

3

4

RG

5

6

H1, H3, H5, H7

H2, H4, H6, H8

7

8

HL

PROGRAMMABLE CLOCK POSITIONS:

1SHP SAMPLE LOCATION.

2SHD SAMPLE LOCATION.

3RG RISING EDGE.

4RG FALLING EDGE.

5H1 RISING EDGE.

6H1 FALLING EDGE.

7HL RISING EDGE.

8HL FALLING EDGE.

Figure 16. High Speed Clock Programmable Locations (HCLKMODE = 001)

Rev. C | Page 15 of 92

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