TI电容隔离技术详解.ppt

Above diagram shows TDDB (Time Dependent Dielectric Breakdown) test results, drawn on a semi-logarithmic scale, time to fail in years over stress-voltage in RMS-volts. A number of devices from different production lots is stressed continuously with voltages exceeding the rated voltage by far. For each test-voltage, the time to fail for the first part failing is noted. The pink dots show ADIs test results taken at 800Vrms through 1200Vrms the non-linear extrapolation results into the 50years lifetime-prediction at 565V peak or ~400Vrms. The green dots show TI’s ISO721 test-points, for quick results taken at much higher voltage. The above shows the same data-points on the same scales, just the extrapolation is linear now. This results into the 28 years lifetime for TI-capacitive couplers, that we specify. With the linear extrapolation, ADI shows significantly less. Furthermore, please note the light-blue data-point: For about 2.5 years, we have 240 parts running at 1000Vrms (Note: that 2.5 times the rated voltage!) without any failures, or in other words, about two orders of magnitude longer surviving compared to the ADuM1100. Power-up and –down behavior is an important criteria for an isolation part. Above diagrams show a ramp in the milli-second range for Vcc1, while Vcc2 is valid already, output is enabled, input is set to low. The ISO721 shows a single transition once sufficient voltage is reached. For power-down, the device assumes the opto-coupler-like failsafe-high in a single transition, once Vcc1 falls below the threshold. Magnetic couplers like the ADuM1100 show oscillation before reaching a steady-state value. Notes for powering up ADUM: In real terms, iCoupler supplies are considered off for values below 2.7 V. Given that supplies have finite rise times, a subtle point is raised: at some value of supply voltage below 2.7 V, a channel may start to operate, albeit not predictably. ADuM1xxx series of iCouplers require rise times for supplies of 0.1 V/μs. EVMs