Open-collector Schottky-clamped output and timing
The HCPL0638R2: The output stage is an open-collector Schottky-clamped transistor that sinks up to 15 mA per channel — the Schottky clamp prevents the collector from saturating deeply, which keeps propagation delay short and repeatable at 75 ns max for both tpLH and tpHL. Rise and fall times are 17 ns and 5 ns typical respectively, so the output edges stay fast enough for 10 Mbps NRZ signalling without excessive duty-cycle distortion. Both input channels are on side 1 (2/0 configuration), meaning the LED drive is referenced to a single supply domain — the second channel does not require its own isolated power, saving board space in multi-channel isolation banks.