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EPC120-QFN16 参数 Datasheet PDF下载

EPC120-QFN16图片预览
型号: EPC120-QFN16
PDF下载: 下载PDF文件 查看货源
内容描述: 完全集成的隔光芯片,带有2线总线接口 [Fully integrated Light-Barrier Chips with 2-Wire Bus Interface]
分类和应用:
文件页数/大小: 27 页 / 550 K
品牌: EPC [ ESPROS PHOTONICS CORP ]
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epc120  
1. Application Information  
The epc120 chip set is a general purpose CMOS integrated circuit for light barrier applications. Up to 1023 devices may be connected to two  
respectively four wires in parallel. Each device can be individually addressed by an epc100 chip which acts as the interface between a  
microcontroller and the 2-wire bus. It manages the bus traffic between the microcontroller and the individual epc120 elements. Programmable  
fuses i.e. for the address, sensitivity, LED light pulse width, etc. allow the device to be parametrized in the final system (OTP memory).  
The bus controller activates the emitting side of the epc120 and reads the status of the levels at the photodiode input. The status of the  
answers to the interface chip can be 'no light pulse received', 'low level light pulse received' and 'high level light pulse received'.  
Each chip can be put into 'standby mode' or 'operating mode' to reduce power consumption. During 'standby mode', power consumption is  
reduced and the photo diode is shorted. In the 'operation mode', the device is active and ready to receive a light pulse generated by an LED  
activated by the LED pin. During a scan, the bus controller addresse s one device after the other and fetches the light barrier status.  
This manual describes the various operation and programming modes in order to use epc120. For the interface chip epc100 please refer to  
the epc10x “Reference Manual”.  
2. Hardware Design Information  
Figure 2 shows the epc120 as an example in a long range light barrier application as a single bus module in a bus-chain configuration with  
minimal part count. The LED emits a light pulse when the chip is addressed by the bus controller. Light of the LED is reflected from a  
reflecting object or a retro reflector back to the photo diode PD. If the received light is strong enough it triggers the internal thresholds  
OUTN/H. The status of the receiver result can be read by the bus controller.  
VDD Track for LEDs  
VDD for 2-Wire Bus (Data & Power)  
1st Bus Module  
nth Bus  
Module  
R1  
100R  
R2  
10k  
VDD  
epc120  
T2  
BC807-40  
VDD33  
VDD18  
PD  
CS  
LED/SCK  
T1  
BC846  
SI  
SO  
C1  
100μF  
Low ESR  
C3  
C4  
IR LED, i.e.  
TSML1000  
GND  
100nF 4.7nF  
R3  
2R2  
i.e.  
epc300  
PD  
GND 2-Wire Bus (Data & Power)  
GND Track for LEDs  
Figure 2: Long range light barrier chain application with minimal part count  
The output to drive the LED is a current source capable to drive typically 1mA. For a high performance light barrier, an LED peak current of  
up to 2A is needed. To generate such a high LED current, an external amplifier is necessary. The circuitry in Figure 2 is a simple  
implementation of such an amplifier. The complementary Darlington circuit with T1 and T2 and R2 and R3 does the job. In order to avoid  
interference on the supply voltage, the supply is isolated (filtered) with R1 and C1. The high peak LED pulse current is delivered by the  
capacitor C1, which itself is charged more or less constantly by R1. Make sure, that there is no coupling of the high LED current to the ground  
and the supplies of the epc120 or to the cathode of the photo diode. This driver amplifier operates with a VDD LED in a range of 5 to 30 VDC.  
Design Precautions  
The sensitivity at pin PD is very high in order to achieve a long operation range of light barriers even without  
lenses in front of the IR LED and/or the photo diode. Thus, the pin PD is very sensitive to EMI. Special care  
should be taken to keep the PCB track at pin PD as short as possible (a few mm only!). This track should be  
kept away from the IR LED signal tracks and from other sources which may induce unwanted signals. It is  
strongly recommended to cover the chip, the photodiode and all passive components around the chip with a  
metal shield. A recommended part is shown in Figure 3. The pins at the bottom are to solder the shield to  
Figure 3: Recommended EMC  
the PCB with electrical connection to GND. The hole in the front is the opening window for the photo diode.  
shield  
The back side of the PCB below the sensitive area (PD, epc120) shall be a polygon connected to GND to  
shield the circuit from the back side as well.  
Ambient Light  
Photodiode DC current can be generated by ambient light, e.g. sun light. DC currents at pin PD do not generate a DC output signal. However,  
if IPDDC is above the stated maximal value, the input is saturated which blocks the detection of AC current pulses.  
© 2011 ESPROS Photonics Corporation  
Characteristics subject to change without notice  
5
Datasheet epc12x - V2.1  
www.espros.ch