I guess it has to do with the low-voltage process, but it does take away the open drain's most interesting feature.Ī totem pole driver or output is fast and relatively 'powerful' when switching in either direction compared to passive resistor stages or current source or open collector loaded stages.Ī totem pole arrangement is not suitable for paralleling with other divers to make 'wired OR' stages - which can be useful in some applications.Ī totem pole driver switches 'between its supply rails' so cannot drive loads which are connected on one end to voltages outside the supply rails - as is required in some applications. When the load you're driving goes beyond \$V_\$.CMOS totem-poles are more symmetrical, and don't suffer from this. So don't use them when you need to both source and sink current. TTL totem-poles are highly asymmetrical: they can hardly source current, typically 0.4mA versus 16mA when sinking.
Always use open collector/open drain drivers for wired AND. If one output is high and the other low you get a short. You can't use totem-poles for wired AND (often called wired OR, but most often they're ANDs).
