MT9M019 Aptina Imaging Corporation, MT9M019 Datasheet - Page 36

• Manufacturer Part Number: MT9M019
• Description: 1/5-Inch 1.3Mp CMOS Digital Image Sensor
• Manufacturer: Aptina Imaging Corporation

Analog Gain
Using Per-color or Global Gain Control
SMIA Gain Model
Aptina Gain Model
PDF: 7723845879/Source:2828556980
MT9D019_DS - Rev. F 5/10 EN
gain
=
analogue_gain_m0
------------------------------------------------------------------------------------------------------
gain
The MT9M019 provides two mechanisms for setting the analog gain. The first uses the
SMIA gain model. The second uses the traditional Aptina gain model. The following
sections describe both models, the mapping between the models, and the operation of
the per-color and global gain control.
The read-only analogue_gain_capability register returns a value of 1, indicating that the
MT9M019 provides per-color gain control. However, the MT9M019 also provides the
option of global gain control. Per-color and global gain control can be used interchange-
ably. A write to a global gain register is aliased as a write of the same data to the four
associated color-dependent gain registers. A read from a global gain register is aliased to
a read of the associated green1/greenR gain register.
The read/write gain_mode register required by SMIA has no defined function in the
SMIA specification. In the MT9M019 this register has no side-effects on the operation of
the gain; per-color and global gain control can be used interchangeably regardless of the
state of the gain_mode register.
The SMIA gain model uses the following registers to set the analog gain:
• analogue_gain_code_global
• analogue_gain_code_greenR
• analogue_gain_code_red
• analogue_gain_code_blue
• analogue_gain_code_greenB
The SMIA gain model requires a uniform step size between all gain settings. The analog
gain is given by:
The Aptina gain model uses the following registers to set the analog gain:
• global_gain
• green1_gain
• red_gain
• blue_gain
• green2_gain
This gain model maps directly to the control settings applied to the gain stages of the
analog signal chain. This provide a 7-bit gain stage and a 2X gain stage. As a result, the
step size varies depending upon whether the 2X gain stage is enabled. The analog gain is
given by:
analogue_gain_c1
=
(
<color>_gain[7]
×
analogue_gain_code
+
1
36
MT9M019: 1/5-Inch 1.3Mp CMOS Digital Image Sensor
)
×
<color>_gain[6:0]
------------------------------------------- -
=
analogue_gain_code_<color>
---------------------------------------------------------------------- -
16
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8
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