AEC-Q101 photocoupler for the 125°C bus
The TLX9309(TPL,F is a single-channel DC-input transistor-output photocoupler from Toshiba's Automotive series, qualified to AEC-Q101. Isolation is rated at 3750Vrms, which covers the galvanic separation needed between the high-voltage traction bus and the low-voltage control domain in an inverter or DC-DC converter. The 6-SOIC 5-lead package (4.55 mm body width) fits the same footprint as other Toshiba SO6 photocouplers, so a board already laid out for the TLX9000 family accepts this part without a spin.
CTR spread and what it means for the sense threshold
Current transfer ratio is specified from 15% minimum to 300% maximum, both measured at 7 mA forward current. The wide spread means the designer sizes the pull-up resistor and the downstream logic threshold for the 15% floor — at 7 mA in, the output transistor sinks at least 1.05 mA. The 300% ceiling (21 mA out at 7 mA in) is the saturation limit; the output does not need to sink more than 25 mA continuous per channel. Forward voltage is 1.6 V typical, and the maximum DC forward current is 15 mA. Driving the LED at 7 mA (the CTR test condition) gives a good balance between isolation lifetime and output drive margin — running at the 15 mA ceiling reduces the LED's long-term light output due to degradation, which matters in a 15-year automotive lifecycle.
Active production — sourcing for the BOM line
No pin-compatible second-source is listed from another manufacturer, but the TLX9000(TPL,F from the same Toshiba family shares the same SO6 footprint and 3750Vrms isolation rating — a functional cross-reference for a BOM hedge when needed.