OV8825 Camera Application Notes R1.16

OV8825 Camera Module Application Notes

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Related Documents (4)

1. Overview of OV8825 Applications (5)

2. Hardware Design of OV8825 Camera Module (6)

2.1 Camera Module with 4 lane MIPI Interface (6)

2.1.1 Description of Camera Interface (7)

2.1.2 PCB/FPCB Layout Guide (8)

2.2 Camera Module with 2 lane MIPI Interface (9)

2.2.1 Description of Camera Interface (10)

2.2.2 PCB/FPCB Layout Guide (10)

2.3 Deal with Lens (11)

2.3.1 Light fall off (11)

2.3.2 F# of Lens (11)

2.3.3 Focus Accuracy at infinite (11)

2.3.4 Optical contrast (11)

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2.4 Calibration of Camera Module (11)

5.1.2.1 Preview 1632x1224 30fps 408Mbps/Lane (26)

5.1.2.2 Capture 3264x2448 24fps 528Mbps/Lane (27)

5.1.2.3 Video 1080p Full FOV 30fps 408Mbps/Lane (29)

5.1.2.4 Video 720p Full FOV 60fps 528Mbps/Lane (31)

5.1.3 Settings for 2 Lane MIPI (32)

5.1.3.1 1632x1224 30fps 720Mbps/Lane (32)

5.1.3.2 3264x2448 15fps 656Mbps/Lane (34)

5.1.3.3 1920x1080 30fps 720Mbps/Lane (36)

5.1.3.4 1280x720 60fps 456Mbps/Lane (37)

5.1.4 I/O Control (39)

5.1.5 Drive capability (39)

5.1.6 Mirror and Flip (39)

5.1.7 BLC (Black Level Calibration) (40)

5.1.8 Defect Pixel Correction (41)

5.1.9 Lens Correction (41)

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5.2 Load Calibration Data (42)

5.3 Driver Functions (50)

“Camera Module Image Quality Evaluation Procedure and Criterion – RAW Sensor”

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OV8825 is a 1/3.2 inch high performance 8M camera supporting 4 lane MIPI interface. It can be

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1.7~3.1V of sensor digital IO power (clean). 1.8V is recommended.

1.5V of sensor core power (clean). The sensor internal regulator (no external 1.5V DVDD is needed) is recommended for 1.8V DOVDD. External 1.5V DVDD is recommended for

2.8V DOVDD.

Digital ground. AGND and DGND should be separated and connected to a single point outside camera module (Do not be

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1. EVDD/EGND are power/ground for MIPI core. DGND and EGND should be two separated nets, 3. If more space available, use 1uF-0402 capacitor between DVDD and DGND.

5. The traces of MCP, MCN, MDPx, and MDNx should have the same or similar length. The impedance transmission lines should be controlled at 100 Ohm. The differential pairs should be separated from other wires at least 3 space(no matter in same layer or opposite layer) or with guarded ground wires. Try to minimize number of vias on differential pairs and keep number of

6. The traces from AF_VCC to L1+ and L1- to pin VCMISNK, and the trace of AF_AGND

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7. AVDD and DOVDD should be separated from clock wires as XVCLK, SCL, SDA, no matter in

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1.7~3.1V of sensor digital IO power (clean). 1.8V is recommended.

1.5V of sensor core power (clean). The sensor internal regulator (no external 1.5V DVDD is needed) is recommended for 1.8V DOVDD. External 1.5V DVDD is recommended for

2.8V DOVDD.

Digital ground. AGND and DGND should be separated and connected to a single point outside camera module (Do not be

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Light fall off means the corner of image is darker than center of image. It is caused by CRA of image sensor and CRA of lens. The RI (relative illuminant) is a index to measure light fall off of The lens shading correction function of OV8825 could be turned on to apply extra gain to compensate the corner brightness and make the whole picture looks same bright. The extra gain cause extra noise at corners of image. So actually RI reflects corner noise at bright condition. To reduce corner noise at bright condition, it is recommended to select lens with higher RI.

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The lens shading also varies from one camera module to another. To compensate lens shading variation, lens shading calibration is done at camera module level and calibration data is stored in OTP of OV8825 or EEPROM built-in camera module. The calibration data could be OV8825 lens correction calibration data or ISP lens correction calibration data. The calibration data could be loaded from camera module and applied to OV8825 or ISP when camera module is used on phone.

The lens position vs VCM setting also varies from one camera module to another. It could be For detail information of OV8825 camera module calibration and how to use calibration data,

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Host provide 4 powers to OV8825 camera module. To minimize power consumption of phone, avoid using regulators for camera and VCM power supplies. DC-DC type power supply are highly

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90mA (DVDD from internal regulator)

10mA (DVDD from external regulator)

Strobe and Shutter could be used to control LED driver. Strobe is used to sync LED with

OV8825 exposure. Shutter could be used as general GPIO to control torch mode and flash mode of LED driver. Below is a sample schematic of OV8825 interface with LED driver – AS3685A.

3.1.6 PCB layout Guide of Host

1. The traces of MCP, MCN, MDPx, and MDNx should have the same or similar length. The impedance transmission lines should be controlled at 100 Ohm. The differential pairs should be separated from other wires at least 3 space(no matter in same layer or opposite layer) or with guarded ground wires. Try to minimize number of vias on differential pairs and keep number of vias same for all differential pairs.

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The lens cover is the cheapest part in optical path. But it could affect picture quality very much. The lens cover should be made with optical glass with AR coating at both side. Otherwise, the lens The wide angle light (light outside FOV of lens) may cause lens flare which lower contrast of image and cause image looks foggy. So the wide angle light need to be blocked by mechanical

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At most of the time, OV8825 camera module works either in preview mode or video mode. When picture is captured, OV8825 camera module switch to 8M full resolution for several frames, then switch back to preview mode. So the power consumption of capture mode doesn't have much impact on working temperature of OV8825 camera module, while power consumption of preview mode and video mode is more important for working temperature of OV8825 camera module.

If one-shot focus is used, the power consumption of preview is about 352mW. If continuous auto focus is used, the power consumption of preview is about 436mW. If capture 720p/1080p video, the

The worst case power consumption of OV8825 camera module is 628mW(8M@24fps, Macro mode). The heat generated by the power consumption should be dispatched out of camera module.

Heat Conductivity (W/m.K)

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Initialize Camera Module to working mode

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t0: >= 0ms. Delay from DOVDD stable to AVDD stable. It is recommended to power up AVDD

DOVDD, AVDD and DVDD powers are applied. SCL and SDA pins are pulled high, PWDNB

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Turn off DVDD, AVDD and DOVDD. The 3 powers could be turned off simultaneously. If turned off separately, DVDD should be turned off first, then AVDD and DOVDD last.

When OV8825 is powered off, please pull low all input pins (except SCCB pins) to OV8825. If

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any input pin (except SCCB pins) of OV8825 is pulled high, the high input pin may leak current to