MT9V024 datasheet(39/62 Pages) ONSEMI

39 / 62 page

MT9V024_DSRev. G Pub. 4/15 EN

©Semiconductor Components Industries, LLC, 2015.

MT9V024: 1/3-Inch Wide-VGA Digital Image Sensor

Feature Description

Automatic Gain Control and Automatic Exposure Control

The integrated AEC/AGC unit is responsible for ensuring that optimal auto settings of

exposure and (analog) gain are computed and updated every frame.

AEC and AGC can be individually enabled or disabled by R0xAF. When AEC is disabled

(R0xAF[0] = 0), the sensor uses the manual exposure value in coarse and fine shutter

width registers. When AGC is disabled (R0xAF[1] = 0), the sensor uses the manual gain

value in R0x35 or R0x36. See “Pixel Integration Control” on page 24 for more informa-

tion.

Figure 29:

Controllable and Observable AEC/AGC Registers

The exposure is measured in row-time by reading R0xBB. The exposure range is

1 to 2047. The gain is measured in gain-units by reading R0xBA. The gain range is

16 to 63 (unity gain = 16 gain-units; multiply by 1/16 to get the true gain).

When AEC is enabled (R0xAF), the maximum auto exposure value is limited by R0xBD;

minimum auto exposure is limited by AEC Minimum Exposure, R0xAC.

Note:

AEC does not support sub-row timing; calculated exposure values are rounded down

to the nearest row-time. For smoother response, manual control is recommended for

short exposure times.

When AGC is enabled (R0xAF), the maximum auto gain value is limited by R0xAB;

minimum auto gain is fixed to 16 gain-units.

The exposure control measures current scene luminosity and desired output luminosity

by accumulating a histogram of pixel values while reading out a frame. All pixels are

used, whether in color or mono mode. The desired exposure and gain are then calcu-

lated from this for subsequent frame.

When binning is enabled, tuning of the AEC may be required. The histogram pixel count

R0xA5, may be adjusted as required.

EXP. LPF

(R0xA8)

EXP. SKIP

(R0xA6)

Coarse Shutter

Width Total

AEC ENABLE

(R0xAF[0 or 8])

MAX. EXPOSURE (R0xBD)

MIN EXPOSURE (R0xAC)

AEC

UNIT

To exposure

timing control

AEC

OUTPUT

R0xBB

R0xBA

To analog

gain control

HISTOGRAM

GENERATOR

UNIT

AGC

UNIT

GAIN LPF

(R0xAB)

GAIN SKIP

(R0xA9)

MANUAL GAIN

A or B

AGC ENABLE

(R0xAF[1 or 9])

AGC OUTPUT

MAX. GAIN

(R0xAB)

MIN GAIN

DESIRED BIN

(desired luminance)

(R0xA5)

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