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Functional Description (continued)

8.0

SIGNAL PROCESSING

8.1

Bad Pixel Detection & Correction

The LM9627 has a built-in bad pixel detection and correction

block that operates on the fly. This block can be switched off by

the user.

8.2

Black Level Compensation

In addition to the programmable gain the LM9627 has a built in

black level compensation block as illustrated in Figure 25. This

block can be switched off.

Figure 25. Digital Black Level Compensation.

The black level compensation block will subtract the average

signal level of the black pixels around the array from the digital

video output to compensate for the temperature and integration

time dependent dark signal level of the pixels. The exponential

averaging circuit shown in figure 25 only operates on the least

significant 8 bits of the video data.

9.0

POWER MANAGMENT

9.1

Power Up and Down

The LM9627 is equipped with an on-board power management

system allowing the analog and digital circuitry to be switched

off (power down) and on (power up) at any time.

The sensor can be put into power down mode by asserting a

logic one on the “pdwn” pin or by writing to the power down bit in

the main configuration register via the I

2C compatible serial

interface.

To power up the sensor a logic zero can be asserted on the

“pdwn” pin or write to the power down bit in the main configura-

tion register via the I

2C compatible serial interface.

It will take a few milli seconds for all the circuits to power up. The

power management register contains a bit indicating when the

sensor is ready for use. During this time the sensor cannot be

used for capturing images. A status bit in the power manage-

ment register will indicate when the sensor is ready for use.

9.2

Advanced Power Features

In addition to the power up/power down features of the sensor,

sections of the analog video processing chain can be powered

down and re-routed during normal operation. This flexibility

allows power dissipation to be traded of with signal gain as

shown in the table below:

Figure 26. Power Control

10.0 ANALOG GAIN ADJUSTMENT

The integrated analog programmable gain amplifier is capable

of applying a linear gain 1X to 5.6X in 64 linear steps. This can

be programmed using the VGAIN register as shown in the table

below:

PGA Amp

Power Saving

0mW

off

10mW

*(1-a)

-1

only enabled for black pixels

input signal

VidGain

Dec

Code

VidGain

Hex

Code

Gain

Amp

Value

VidGain

Dec

Code

VidGain

Hex

Code

Gain

Amp

Value

3.34

1.07

3.41

1.15

3.48

1.22

3.56

1.29

3.63

1.37

3.7

1.44

3.77

1.51

3.85

1.58

3.92

1.66

3.99

1.73

4.07

1.8

4.14

1.88

4.21

1.95

4.29

2.02

4.36

2.1

4.43

2.17

4.5

2.24

4.58

2.31

4.65

2.39

4.72

2.46

4.8

2.53

4.87

2.61

4.94

2.68

5.02

2.75

5.09

2.83

5.16

2.9

5.23

2.97

5.31

3.04

5.38

3.12

5.45

3.19

5.53

3.26

5.6

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