I have had the bellow circuit designed with the intention of switching the high side of a 12v automotive relay:

enter image description here

Now I've realised I need the option to switch the low side of relays, as sometimes I have no access to the live wiring or can't control it.

However I don't want to add any extra connectors, so I need to have one output pin that switches between high(14v) and low. (I think the correct term would be a half bridge?)

Can I just add a BTS3134N like the following:

enter image description here

The FPF2700 is active low and the BTS3134N seems to be active high so it would be impossible for them to be turned on at the same time.

Or could I use a H bridge IC such as the L6206Q which lets me control both outputs to High, Low and High impedance. But i'm concerned as I'm not sure if it is designed to supply current from both outputs at the same time.

  • \$\begingroup\$ Schematic of what you propose please. \$\endgroup\$ – Andy aka May 24 '17 at 13:15
  • \$\begingroup\$ They WILL be turned on for the same tame for something about 100ns each time you switch from ON to OFF because of the propagation delays and turn off time. During this you will short your power supply and depend only on current protection of these ICs, which is not a very good idea. Either control them with separate signals and ensure a valid dead time, either use some half bridge siwtches with drivers that assure the proper dead time. \$\endgroup\$ – Todor Simeonov May 24 '17 at 13:46
  • \$\begingroup\$ I agree with Todor, try to define I/O functions and values then behaviour to make a "spec" with constraints of MUST have and Nice To have , rather than will this fuzzy or novel idea work? \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 May 24 '17 at 14:56
  • \$\begingroup\$ I have now updated with the proposed schematics \$\endgroup\$ – B.Baker May 25 '17 at 19:31

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