Operation of the PWM circuit 17 and the power switches 15, 16 are similar to FIG. 1, except that the recirculation phase is performed by the second power switch 16 by BACKGROUND Most cameras have an autofocus mechanism in which an autofocus algorithm processor determines an optimum position of a variable focal length lens that is expected to yield an image of Figure 6 shows a conceptual block diagram of a piezoelectric solution for lens driving. Region India Korea Singapore Taiwan Languages English 简体中文 日本語 Руccкий English 简体中文 日本語 Руccкий Open Menu Parametric Search Amplifiers ADC Drivers Fully Differential Amplifiers Single-Ended Amplifiers (Op-Amp) Single-Ended to Differential Amplifiers
The coil 5 as part of the VCM 3 and camera lens actuator thus converts this current into movement to a given position. The communications interface 13 may be a digital interface that complies with the I2C Specification, Rev. 03, 19 Jun. 2007, and may be on-chip with the power switches 15, 16, and The spring returns the lens to the infinite-focus position, and no power is dissipated unless focusing is required. Can you confirm that a 0.1 uF capacitor is connected from its output to AGND................ http://www.analog.com/en/analog-dialogue/articles/lens-drivers-focus-in-camera-modules.html
Existing Solutions Limitations ... The latter includes a first power switch to selectively conduct current from the VCM node to the power supply node during a current recirculation phase of switch mode operation. With autofocus becoming a standard feature, ever-increasing resolution will call for more camera features, such as optical zoom, shutter control, and image stabilization (Figure 1). The lens driver has many possible inputs and outputs.
ADI holds over 2200 patents, nearly 800 patents pending and has invested over $9 billion in signal processing R&D over the past 50 years. These three digital lines may be used by an off-chip processor that has been programmed to configure or program a duty cycle of the PWM circuit 17 in order to set Questions:1) Is the VCM decoupled with 0.1 uF to AGND?2) Is your circuit exactly the same as what is shown in figure 79..............including component values . Examples of such host devices are dedicated digital still and video cameras, desktop computers, smart phones, tablet computers and other consumer electronic devices that have camera functionality.
Note the common-mode servo option should be disabled (i.e. 0x0F bit=0 ) .Like • Show 0 Likes0 Actions Related ContentRetrieving data ...Recommended ContentWhen does l_clk become stable?Issues with the sruSC589.h in Mems Lens Actuator Gary Casey Related Products AD9822 Complete 14-Bit CCD/CIS Signal Processor AD5398 120 mA, Current Sinking, 10-Bit, I2C D/A Converter AD5821 120 mA, Current Sinking, 10-Bit, I2C® DAC Region Korea India Taiwan The other terminal B of the VCM 3 may be directly connected to a camera VCM node 6. Spring-preloaded voice-coil stroke vs.
The communications interface 13 may contain registers that can be programmed to store a desired PWM duty cycle setting, with which the PWM circuit is programmed. A complete VCM-driver solution, the AD5398 comprises a 10-bit digital-to-analog converter (DAC) with 120-mA output-current-sink capability, intended for driving voice-coil actuators in applications such as lens autofocus and image stabilization. The camera module of claim 8 wherein the switch mode current control circuit comprises a pulse width modulation circuit, PWM, circuit that is coupled to control first and second power switches The camera module of claim 8 wherein the driver circuit and the communications interface are in the same integrated circuit package. 10.
We will discuss the lens driver’s role, describe two useful new products, and consider the future of lens drivers in the marketplace. The piezoelectric actuator is mechanically simple, can make rapid movements, and is energy efficient. The first and second power switches 15, 16, in this example, share a common node that is directly connected to the VCM node 6 as shown. It is contemplated that the invention includes all systems and methods that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in
Other embodiments are also described and claimed. A pulse width modulation circuit controls the first and second power switches. Shutdown Mode Shutdown mode is entered when VDD is between 2.3 V and 3.6 V, and the SHUTDOWN pin is active (low for the AD5823, high for the AD5823-1).
The temperature coefficient of the DAC resistors and that of RSENSE are matched; therefore, the output drift over temperature is minimized. These factors all tend to make the current crop of steppers unsuitable for camera modules in phones. Technical Articles MS-2663-1: Powering the Isolated Side of Your Half-Bridge Configuration Technical Articles MS-2318: Design Fundamentals of Implementing an Isolated Half-Bridge Gate... Figure 6.
The driver circuit may be implemented in a six-pin integrated circuit package and may be used for controlling the VCM of an autofocus lens actuator. It is mechanically robust, shock-resistant, and has low-cost mechanics. Diode D1 is an output protection diode. The electronic device of claim 13 wherein the VCM coil current does not reverse direction for the full range of movement of the camera lens. 15.
FIG. 1 is a circuit schematic of a driver circuit 2, in accordance with an embodiment of the invention. The above summary does not include an exhaustive list of all aspects of the present invention. Analog.comEngineerZoneWikiLinear.comCareers Global Please Select a Region India Korea Singapore Taiwan LanguagePlease Select a LanguageBrowser Compatibility Issue: We no longer support this version of Internet Explorer. It can be seen that the steady state average current is a function of the duty cycle, such that as the duty cycle is increased the average VCM current is also
An autofocus algorithm processor 24 obtains sample digital images from the image processor 22, and analyses them in accordance with known autofocus algorithms to determine a sharpness parameter. Images(6)Claims(15) What is claimed is: 1. It should be noted that references to “an” or “one” embodiment of the invention in this disclosure are not necessarily to the same embodiment, and they mean at least one. In another embodiment, one of the two VCM terminals is coupled to the VCM node of the driver circuit while the other is directly connected to the power return node.
FIG. 5 is a circuit schematic of the driver circuit, according to another embodiment of the invention. Figure 2.