Explanation

LX1970 is a sensor with a new technical lamp with spectral response to imitate human eyes. This device is the system of monitoring ideal equipment brightness control in the system of environmental light flat display. It has a unique photoelectric diode configuration (patent to be determined) peak response at 520 nm and the two types of ultraviolet rays and infrared wavelengths. The photoelectric sensor is a PIN diodes accurate, linearly repeated current transmission function. Optical current multiplication is available to integrated high -gain amplifiers and IS on the two output pins; one A current source and another current remittance. These currents are easy to convert through one or two outputs. The voltage gain is generally within the range of 10kΩ to 50kΩ from the resistance value. There are accurate internal gain amplifiers, high design complexity, and high cost.

Main features

Application

spectral response

Low infrared sensitivity

High accuracy amp; amp; 123] Repeatable output current and light

Voltage can be adjusted

Temperature stable

Integrated high -gain photo

current discharge

complementary complement Current

Output

does not require filter

Application

Palm on the palm

LCD TV

Tablet Computer

Mobile

Absolutely maximum. ] SNK/SRC (output compliance voltage) -0.3 to VDD+0.3VDC

SNK/SRC (maximum output current) Internal Co., Ltd. 85 ° C

Storage temperature range -40 to+100 ° C

The peak temperature of the weld backflow (welding 10 seconds) 240 ° C

Note: If these rated values u200bu200bmay be possible, it may be possible It will damage the device. All voltages are grounded with

. The current is a positive input and a negative output specified terminal.

Welding backflow: IPC/JEDEC J-STD-Std-Sn-PB Small Small Small Substitute

Unless otherwise regulations, the following specifications are suitable for working environment temperature -40 ° C -40 ° C ≤TA ≤85 ° C, VDD u003d 2V to 5.5V, load u003d 50kohms, direct light input 2 to 14.6μW/cm2

Unless otherwise explained. The performance is between -40 ° C and 0 ° C, and through design and representation, it can ensure between 70 ° C and 85 ° C.

Note 2: The input radiation degree is provided by the white light emitting diode (LED) light source, and adjusts to the 555nm surface of 14.6 μW/cm2 on the sensor.

Note 3: See Figure 1

Note 4: See Figure 2

Application Notes

Lighting Equipment [ 123]

Conversion from μW/CM2 is necessary to define the light source for NITS. The unit brightness of the unit means the lighting of the unit. Microva/square centimeter is a radiation flux that is visible and invisible to the radiation degree or electromagnetic measurement. The first step conversion process is to convert the radiation degree to illuminance, which essentially includes the radiation degree that runs through the sensor of the sensor. Use the bright vision curve in a normal environment, and use the dark vision (dark adaptive eye) in the dark environment. If the light is synthesized only one wavelength, the conversion chart will tell the conversion coefficient that converts μW/m2 to LUX (lingering/m2). If multiple wavelengths are used, the spots of the spectrum must be applied to the synthetic illuminance on the sensor filter. The wavelength of the most sensitive person adapts to the normal light is 555 Nm. At 555nm, the conversion factor is 683lux u003d 1 watt/square meter u003d 100 μW/cm2. Therefore, 14.6 μW/CM2 u003d 100 Lax is at 555nm. The next step of the conversion process is the transition illuminance to brightness. The photo unit is Lx or the lumen/m2 brightness unit is Nit or the flow/m2/mirin hormone. Assuming that the illuminance falls on the Langbo surface, it has a complete dispersal and complete reflection, from LUX to NITS to 3.14lux Langbo reflective mirror generates 1 nit. So 100 Lax produces 31.4 Nit. If the light sensor has a real optical response, it will be the same number of NIT or Lax, regardless of the color of the light. However, because the matching is not perfect, there is still a wavelength dependence, especially at the end of the visible spectrum. In the case of LX1970, the peak light response is 520nm, but the ""white"" light perceived by different people's eyes based on the light source may actually be the peak wavelength of the synthetic refers to 520nm. For example, a typical fluorescent lamp includes not only nearby main light 550nm, but also 404 and 435nm. The source of incandescent lights such as standard tungsten lamp generated a large amount of infrared radiation exceeding 2000Nm.

Application information

LX1970 is a light sensor with spectral response like a human visual system. It is packed in removing the MSOP package. Microsemi also offers LX1971 with the same pins output and similar power supply voltage range LX1970 light sensor. LX1971 response ability but LX170 different. Generally speaking, LX1971 has low sensitivity and wide dynamic range. The response capacity of LX170 is proportional to the receptor's strength and the intensity of light in the photo. Although the gain depends on the general speaking, the sensitivity of the wavelength and direction of light (5nm) is yellow, and the wavelength is: L LT; 1200 Lax, iOUT u003d L × 0.76 μALX1970 is most suitable for the component control system for continuous lighting. For example, in the LCD backlight application, the brightness level of the backlight should be adjusted according to the level of environmental lighting; the LX170 can provide a closed -loop brightness control system. For most indoor applications, the LX170 of 1200 Lax's saturated point is usually not a restriction. LX1971 is most suitable for the system that the system must respond to the ability to see clearly. For example, the sensor to be rotated adjusts the reflectivity rearview mirror of the rearview mirror on the front light or sensor. These systems require the sensor dynamic range is similar to the sight. Like human eyes, LX1971's square root function makes it particularly sensitive to slight changes under lower light. The extensive dynamic range allows LX1971 to perceive the dusk and sunlight or sunlight and dense clouds. The first curve shows the formula -based LX1970 without load resistance. It can be used as a baseline guide to calculate the gain setting resistor. The compliance output of the current source may cause prematured saturation when the output is increased when the load resistance is increased. SRC compliance voltage is usually specified as VDD-350MV@s s s. The second curve displays the output saturation VIN u003d 5V and 10K resistance SRC ground. When the output becomes non -linearly, the output becomes non -linearly when it starts.

Application instance

The following example shows two fully automatic (non -user input) and semi -automatic re -reinforcement. These general criteria are suitable for various potential light control applications. LX1970 can be used to control the brightness input of the CCFL inverter (such as the Microsemi group stage #8482; inverter series or controller IC series). Similarly, it can sink LED drives like LX1990 and LX1991, or boost drives like LX192 and LX1993. In each specific application, you must realize that LX1970 needs to be used for the target environment and its environmental light conditions. The mechanical installation pore size of the sensor and lights, the use of the light pipe or baffle is important. Determine the exposure of the LX170 on the given

FIG. Automatic lighting solutions without user interaction. Select the minimum brightness required for R1 and the R2 value slope. Select C1 to adjust the response time and filter 50/60 Hz interior lighting. For example, assuming you want to generate an input of the output voltage driver of 0.25V to 1.25V. 0.25 il means the smallest LED brightness and 1.25V representationMaximum value. The first step is to determine the ratio of R1 and R2.

Next, the value of R2 can be based on the maximum output source current from LX1970. Under the maximum light of the application, it is assumed that this is determined to be about 50 μA. Therefore, R2 can be calculated as follows:

When the output node actually reaches 1.25V, the power supply will provide a current of 6 μA from about R1. This assumes that the LED driver's high impedance input. In Figure 3, the user has added adjustable deviation control to allow the minimum and maximum output voltage to allow control. This allows users to adjust the output brightness within a limited range according to personal preference. PWM input sources can of course be replaced with equivalent DC voltage.

FIG. 4 shows how to complete the full manual coverage quickly to add to the example in FIG. 3. In addition to the door opening and closing LX1970, the diode has been inserted and closed LX1970.

The previous example is only a small part of the sensor. For example, because a free receiver outputs a resistor from VDD to SNK may generate a fixed reference voltage to a fixed reference voltage and develop a logical shutdown signal. If the application uses a signal such as Transfilter or a reflective LCD monitor, it will make the backlight or front lighting ambient light of the display when it reaches sufficient brightness.