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HCPL-5300 Datasheet(PDF) 9 Page - AVAGO TECHNOLOGIES LIMITED |
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HCPL-5300 Datasheet(HTML) 9 Page - AVAGO TECHNOLOGIES LIMITED |
9 / 15 page 9 CMR With The LED Off (CMRH) A high CMR LED drive circuit must keep the LED off (VF ≤ VF(OFF)) during common mode transients. For example, during a +dVCM/dt transient in Figure 18, the current flowing through CLEDN is supplied by the parallel combination of the LED and series resistor. As long as the voltage developed across the resistor is less than VF(OFF) the LED will remain off and no common mode failure will occur. Even if the LED momentarily turns on, the 100 pF capacitor from pins 6-5 will keep the output from dipping below the threshold. The recommended LED drive circuit (Figure 13) provides about 10 V of margin between the lowest optocoupler output voltage and a 3 V IPM threshold during a 10 kV/ s transient with VCM=1000 V. Additional margin can be obtained by adding a diode in parallel with the resistor, as shown by the dashed line connection in Figure 18, to clamp the voltage across the LED below VF(OFF). Since the open collector drive circuit, shown in Figure 19, cannot keep the LED off during a +dVCM/dt transient, it is not desirable for applications requiring ultra high CMRH performance. Figure 20 is the AC equivalent circuit for Figure 16 during common mode transients. Essentially all the current flowing through CLEDN during a +dVCM/dt transient must be supplied by the LED. CMRH failures can occur at dv/dt rates where the current through the LED and CLEDN exceeds the input threshold. Figure 21 is an alternative drive circuit which does achieve ultra high CMR performance by shunting the LED in the off state. IPM Dead Time and Propagation Delay Specifications These devices include a Propagation Delay Difference specification intended to help designers minimize “dead time”in their power inverter designs. Dead time is the time period during which both the high and low side power transistors (Q1 and Q2 in Figure 22) are off. Any overlap in Q1 and Q2 conduction will result in large currents flowing through the power devices between the high and low voltage motor rails. To minimize dead time the designer must consider the propagation delay characteristics of the optocoupler as well as the characteristics of the IPM IGBT gate drive circuit. Considering only the delay characteristics of the optocoupler (the characteristics of the IPM IGBT gate drive circuit can be analyzed in the same way) it is important to know the minimum and maximum turn-on (tPHL) and turn-off (tPLH) propagation delay specifications, preferably over the desired operating temperature range. The limiting case of zero dead time occurs when the input to Q1 turns off at the same time that the input to Q2 turns on. This case determines the minimum delay between LED1 turn-off and LED2 turn-on, which is related to the worst case optocoupler propagation delay waveforms, as shown in Figure 23. A minimum dead time of zero is achieved in Figure 23 when the signal to turn on LED2 is delayed by (tPLHmax - tPHLmin) from the LED1 turn off. This delay is the maximum value for the propagation delay difference specification which is specified at 500 ns for the HCPL-530X over an operating temperature range of -55° C to +125° C. Delaying the LED signal by the maximum propagation delay difference ensures that the minimum dead time is zero, but it does not tell a designer what the maximum dead time will be. The maximum dead time occurs in the highly unlikely case where one optocoupler with the fastest tPLH and another with the slowest tPHL are in the same inverter leg. The maximum dead time in this case becomes the sum of the spread in the tPLH and tPHL pro- pagation delays as shown in Figure 24. The maximum dead time is also equivalent to the difference between the maximum and minimum propagation delay difference specifications. The maximum dead time (due to the opto- couplers) for the HCPL-530X is 670 ns (= 500 ns - (-170 ns)) over an operating temperature range of -55° C to +125° C. |
Similar Part No. - HCPL-5300_12 |
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Similar Description - HCPL-5300_12 |
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