Application Examples - Vishay

1 Vishay SEMICONDUCTORSO ptocouplers and Solid-State RelaysApplication Note 02 Application ExamplesAPPLICATION NOTE Rev. , 07-Nov-111 Document Number: 83741 For technical questions, contact: DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENTARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT are used to isolate signals for protection andsafety between a safe and a potentially hazardous orelectrically noisy environment. The interfacing of theoptocoupler between digital or analogue signals needs to bedesigned correctly for proper protection. The followingexamples help in this area by using DC- and AC-inputphototransistor IN IC LOGIC DESIGNTo interface with TTL logic circuits, Vishay offers a widerange of 4 pin and 6 pin optocoupler series such as theCNY17x, SFH61xA, TCET110x, or K817P ) Supply voltage: VCC = 5 Vb) Operation temperature range: - 20 C to + 60 Cc) Service life of Application : 10 yearsExample 1:Phototransistor wired to an emitter simplicity, a typical CTR value of 100 % at IF = 10 mA isselected.

2 Within the temperature range of - 20 C to + 60 Cthe CTR undergoes a change between + 12 % and - 17 %.The - 17 % reduction is critical to the functioning of a 10-year service life period of the interfacecircuit, allowance needs to be made for additional CTRreduction of approximately 20 % on account of an additional tolerance allowance of approximately- 25 % for the CTR will result in a safe minimum value ofapproximately 50 %.CTRmin. = 100 % x ( ) x ( ) x ( ) = %For a defined low state at the output of the optocoupler thevoltage VL at RL must be VIL V and currentIIL (IILmax. = mA) must be capable of flowing through RLfrom the TTL to the phototransistor in this case being blocked atthe output of the optocoupler and ICEO maximum 200 nA(at approximately 60 C), the IL - IIL setting can proceedpractically without any results in the following maximum value of RL:A voltage VL at RL resistor of VIH 2 V is necessary in orderto attain a safe high state at the output.

3 This needs to begenerated by the collector current IC of the the case of the TTL output at the input of the optocoupler ,the current should remain IOL 16 mA. The CTR value of50 % results in the maximum output current IC for theoptocoupler of 8 IL = IC + IIH and IIH for standard TTL being maximum,40 A, IL = IC can be assumed without any essential allows the minimum value to be determined for RL:If, for example , RL = 390 is selected and 20 % safety iscomputed to the minimum VIH in respect of the high state(VIH + VIH x 20 % = V), this will then permit IC, IF, and thedropping resistor RV at the input of the optocoupler to bedetermined,With VF = V, (the forward voltage of the IR diode) and VOL V for the TTL output follows:RLILIILIIHVCCVCCRVIFICTTLVL15096 TTLRLVILIIL--------< mA-------------------500 ==RLVIHIL--------->2 V8 mA--------------2 5 0 == V390 ----------------> mA== mA=>>RVVCCVF VOL mA-------------------------------------- --->276 RV270 =,= Application ExamplesAPPLICATION NOTEA pplication Note Semiconductors Rev.

4 , 07-Nov-112 Document Number: 83741 For technical questions, contact: DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENTARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT TTL interface with the optocoupler is able to transmitsignals having a frequency of > 50 kHz or a transmission rateof 100 the same way, the optocoupler can interface with otherlogic circuits, such as LSTTL, HCMOS, or HCTMOS components. All that needs to be done is to work thecorresponding limit values VIH, VOH, IIL, IOL, etc, into thecomputation for the relevant use is made of LSTTL or HCTMOS components this willalso bring about an essential reduction in 2:Phototransistor wired to a collector CTR is determined by applying the same calculation- 50 % - as that given in example 1. In this example ,dimensioning of the interface is launched from the high stateat the output of the the high state a non-operate current of the IIH - ofmaximum 40 A - may flow in the TTL input.

5 If RL selectionis too high, the entire non-operate current = ICEO + IIH mayproduce such a voltage drop through the RL that the criticalVIH voltage (minimum = 2 V) is not if another + 20 % safety is added to the VIH voltage,For calculating the smallest usable RL value, ICmax = 8 mA isassumed as in example 1 and use is made of the low stateof the optocoupler output. In this circuit the current IIL of theTTL input flows through the phototransistor in such a waythat the following applies: IC = IL + results in the following:To select the value for RL, the following should be from the voltage VIL = V, the phototransistoris on the limits of to the voltage VCE being relatively unstable in thisstate, VCE should be selected in such a way that thephototransistor is in full the diagram VCEsat vs. IC in any given 4 pin or 6 pinphototransistor data sheet, CTR reduced by 50 % and forIC < 5 mA follows VCEsat < is now reduced to approximately 4 mA and for theminimum RL follows,If a suitable value is selected for the resistor RL, it is possibleto determine RV at the for RL = k follows:IC = IIL + IL = mAand with CTR = 25 %, IF = IC/CTR = mA:This interface circuit can be used for transmission rates ofup to about 28 kbit/s The fact that considerably lowertransmission rates are possible here compared with thecircuit given in example 1 is partly due to the saturation stateof the phototransistor, and to a large extent, to the highervalue required for 3:Here are other circuit configurations to interface with TTLcircuit, specifically the 7400 ,VIH15097 TTLIIHICRLVCCVIH ICEOIIH+--------------------------<5 V2 V A------------------------7 4.

6 6 k ==RLVCCVIHVIH20 100 +() ICEOIIH+-------------------------------- ---------------------------------------- -------<5 V k ==RLVCCVIL ICmaxIIL --------------------------->5 V mA-----------------------------6 5 6 ==RLVCCVCEsat 4 mA mA ---------------------------------------> 5 () V mA----------------------------------1 8 7 5 ==ILVCCVCEsat mA k mA===RVVCCVF VOL mA-------------------------------------- ---3 1 7 RV330 =,== Application ExamplesAPPLICATION NOTEA pplication Note Semiconductors Rev. , 07-Nov-113 Document Number: 83741 For technical questions, contact: DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENTARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT ACTIVE LEVEL LOW (7400)It is more difficult to operate into TTL gates in the activelevel- high configuration. Some possible methods are asfollows:Obviously, several optocoupler output transistors can beconnected to perform logical : Use smaller pull-up resistorfor higher speed12 k Vcc17454 Note: Best method if negativesupply is availableVCC2 mAV_240 Note: Requires 10 mA fromtransistor and sacrificesnoise margin10 k Note: High sensitivity but sacrificesnoise margin.

7 Needs extra parts174552 k VCCVCC10 k VCCNote: Extra parts cost but, high sensitivity1745610 k VCCA+B7400 Note: Logical OR connectionABA B7400AB17457 Note: Logical AND connectionVCC12 k 12 k Application ExamplesAPPLICATION NOTEA pplication Note Semiconductors Rev. , 07-Nov-114 Document Number: 83741 For technical questions, contact: DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENTARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT DRIVING CIRCUITSThe input side of the optocoupler has an emittercharacteristic as forward current must be controlled to provide thedesired operating input can be conveniently driven by integrated circuitlogic elements in a number of different ACTIVE LEVEL HIGH (7400 SERIES)TTL ACTIVE LEVEL LOW (7400 SERIES)There are obviously many other ways to drive the devicewith logic signals, but a majority can be met with the abovecircuits. All provide 10 mA into the LED, giving 2 mAminimum out of the phototransistor.

8 The 1 V diode knee andits high capacitance (typically 100 pF) provides good noiseimmunity. The rise time and propagation delay can bereduced by biasing the diode onto perhaps 1 mA forwardcurrent, but the noise performance will be INPUT COMPATIBLE OPTOCOUPLERINTRODUCTIONWith the rapid penetration and diversification of electronicsystems, demand for optocouplers is strengthening. Mostpopular are products featuring compact design, low cost,and high added value. To meet the market needs, Vishay isexpanding the optocoupler . This Application note focuseson optocouplers compatible with AC input, and coversconfiguration, principles of operation, and (V)VF(V)IR(tnA)IR( A)1745868 Note: Can omit resistor for about15 mA into diodeVCC17459 Note: More parts required than above270 510 Note: Not as good as above recommended2 k VCCVcc330 17460 Application ExamplesAPPLICATION NOTEA pplication Note Semiconductors Rev. , 07-Nov-115 Document Number: 83741 For technical questions, contact: DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE.

9 THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENTARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT (INTERNAL PIN CONNECTION DIAGRAM) Fig. 1 - 4 Pin AC-Input optocoupler Fig. 2 - 4 Pin DC-Input OptocouplerFigure 1 shows the internal pin connection of a 4 pinAC-input SFH620A-x optocoupler TCET1600, K814P series;and figure 2, of a 4 pin DC-input optocoupler TCET1100,SFH61xA-x, and K817P series. The main difference is thatthe AC-input optocouplers incorporate an input circuit withtwo emitters connected in reverse parallel. In the DC-inputoptocoupler one emitter is connected in the input circuit sothat the emitter emits light to provide a signal when a currentflows in one direction(1- > 2 in figure 1) (one-direction inputtype).However, in the configuration shown in figure 2, when acurrent flows in direction 1 to 2, emitter 1 emits light to senda signal, and when it flows from 2 to 1, emitter 2 emits lightto send a signal (bi-directional input type). Namely, even ifthe voltage level between 1 and 2 varies, and the positiveand negative polarities are changed, either of two emittersemits light to send a signal.

10 This means that theone-direction input optocoupler permits DC input only,while the bi-directional input type permits AC input as next section describes the status of output signals whenVac power is directly input to an AC input compatibleoptocoupler via a current limit resistor. example 1: AC/DC converter Fig. 3 - AC-Input-Compatible optocoupler (Bi-Directional Input) Fig. 4 - Conventional optocoupler (One-Direction Input)(Full-Wave Rectification by Means of Diode Bridge) example 2: detection of a telephone bell signal Fig. 5 - AC-Input-Compatible optocoupler (Bi-Directional Input) Fig. 6 - Conventional optocoupler (One-Direction Input)(Rectified by CR Circuit)14A,KA,KCE127102323141259015099 LineVoltageVCC0+ 15100 LineVoltage0+ 0+VCC0+ Ring Line151010+ Ring Line151020+ Application ExamplesAPPLICATION NOTEA pplication Note Semiconductors Rev. , 07-Nov-116 Document Number: 83741 For technical questions, contact: DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE.