4170 Vrms isolation and the transistor-with-base output
The H11A1SR2VM is a single-channel DC-input optoisolator from onsemi with a transistor-with-base output, rated for 4170 Vrms of isolation between input and output.
CTR and switching speed — what they mean for the drive circuit
The minimum current transfer ratio (CTR) is 50% at a forward current of 10 mA. This means that with 10 mA through the input LED, the output transistor can sink at least 5 mA. The CTR sets the minimum input current needed to guarantee the output switches on; for a given load resistor on the output side, you calculate the required If from the CTR floor. The typical turn-on and turn-off times are both 2 µs, which supports switching frequencies up to roughly 100 kHz in digital isolation applications, though the actual data rate depends on the output pull-up resistor and load capacitance.
Surface-mount package and temperature range
Housed in a 6-SMD gull-wing package (supplier device package 6-SMD), this part is designed for standard reflow soldering. The 30 V maximum output voltage and 400 mV maximum Vce saturation mean the output transistor can interface with 5 V, 12 V, or 24 V logic rails with minimal voltage drop across the transistor when on.