收藏本站
Si1120
2.7. Practical Considerations
It is important to have an optical barrier between the LED and the Si1120. The reflection from objects to be
detected can be very weak since, for small objects within the LED's emission angle, the amplitude of the reflected
signal decreases in proportion with the fourth power of the distance. The receiver can detect a signal with an
irradiance of 1 μW/cm 2 . An efficient LED typically can drive to a radiant intensity of 100 mW/sr. Hypothetically, if
this LED were to couple its light directly into the receiver, the receiver would be unable to detect any 1 μW/cm 2
signal since the 100 mW/cm 2 leakage would saturate the receiver. Therefore, to detect the 1 μW/cm 2 signal, the
internal optical coupling (e.g. internal reflection) from the LED to the receiver must be minimized to the same order
of magnitude (decrease by 10 5 ) as the signal the receiver is attempting to detect. As it is also possible for some
LEDs to drive a radiant intensity of 400 mW/sr, it is good practice to optically decouple the LED from the source by
a factor of 10 6 . A Dual-Port Optical Window shown in Figure 16 can accomplish this easily.
If an existing enclosure is being reused and does not have dedicated openings for the LED and the Si1120, the
proximity detector may still work if the optical loss factor through improvised windows (e.g. nearby microphone or
fan holes) or semi-opaque material is not more than 90% in each direction. In addition, the internal reflection from
an encased device's PMMA (acrylic glass) window (common in cellular telephones, PDAs, etc.) must be reduced
through careful component placement. To reduce the optical coupling from the LED to the Si1120 receiver, the
distance between the LED and the Si1120 should be maximized, and the distance between both components (LED
and Si1120) to the PMMA window should be minimized. The PRX50H mode can be used for the Single-Port
Optical Window shown in Figure 16.
Another practical consideration is that system optical leakage, overlay thickness and transmittance, LED efficiency
variation, TXO sink drive and photodiode part-to-part difference all collectively lead to reflectance measurement
variation even under a given proximity condition. For applications requiring PRX pulse width consistency across
multiple systems, factory calibration is recommended. Factory calibration involves taking a reference measurement
against a consistent and reproducible reflective object (such as an 18% gray card) at a fixed distance during
system production testing. Having this reference proximity measurement stored in non-volatile RAM or Flash
allows host software to make necessary adjustments to incoming PRX pulse widths against this reference
proximity measurement. A low background infrared environment is recommended.
For best proximity range performance, the system optical leakage can be characterized during factory calibration.
To do this, a reference proximity measurement is made when it is known that no object is in proximity of the system
at the time of the measurement. The 'no object' reference measurement allows host software to establish the level
of system optical leakage and make the necessary corrections to account for this.
In a similar way, for applications with heavy reliance on ALS accuracy, measurements using reference light sources
during factory calibration can be used to make adjustments to VAMB, VIRL, and VIRH measurements.
Transparent
window
PRX50H Mode
Si1120
Transmit LED
Si1120
Transmit LED
Optical block
Dual-port Optical Window
Internal Reflection Optical block
Single-port Optical Window
Figure 16. Dual-Port and Single-Port Optical Window
Rev. 1.0
15
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
SI1141-A10-GM IC SENSOR IR PROX/AMBIENT 10-QFN
SI1143-A10-GMR SENS IR PROXIMITY AMB LT 10QFN
SI1300BDL-T1-GE3 MOSFET N-CH D-S 20V SC-70-3
SI1302DL-T1-GE3 MOSFET N-CH D-S 30V SC-70-3
SI1303DL-T1-GE3 MOSFET P-CH 20V 670MA SOT323-3
SI1305DL-T1-GE3 MOSFET P-CH G-S 8V SC-70-3
SI1307EDL-T1-GE3 MOSFET P-CH G-S 12V SC-70-3
SI1401EDH-T1-GE3 MOSFET P-CH F-D 12V SC-70-6
相关代理商/技术参数
SI1120-A-GMR 功能描述:近程传感器 Proximity/Ambient Light Snsr w/PWM Out RoHS:否 制造商:Vishay Semiconductors 感应方式:Optical 感应距离:1 mm to 200 mm 电源电压:2.5 V to 3.6 V 安装风格:SMD/SMT 输出配置:Digital 最大工作温度:+ 85 C 最小工作温度:- 25 C 系列:VCNL3020
SI1120EK 功能描述:光学传感器开发工具 Si1120 Eval Kit RoHS:否 制造商:ams 工具用于评估: 接口类型: 最大工作温度:
SI1120-EK 制造商:Silicon Laboratories Inc 功能描述:
SI1125QR 制造商:Thomas & Betts 功能描述:SPLICE AUTO SEIZE
Si1132-A10-GMR 制造商:Silicon Laboratories Inc 功能描述:SENSOR DGTL UV INDEX QFN 制造商:Silicon Laboratories Inc 功能描述:I2C UV Index Ambient Light Sensor
SI1133-AA00-GMR 功能描述:Optical Sensor Ambient 625nm, 525nm, 460nm I2C 10-WFQFN 制造商:silicon labs 系列:- 包装:剪切带（CT） 零件状态:有效 类型:环境 波长:625nm，525nm，460nm 接近探测:无 输出类型:I2C 电压 - 电源:1.62 V ~ 3.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:10-WFQFN 供应商器件封装:10-DFN（2x2） 标准包装:1
SI1140DK 功能描述:位置传感器开发工具 EVAL BRD SI1143-A10-GM RoHS:否 制造商:Microchip Technology 工具用于评估: 接口类型: 工作电压:
SI1141 制造商:SILABS 制造商全称:SILABS 功能描述:PROXIMITY/AMBIENT LIGHT SENSOR IC WITH I2C INTERFACE