Please read the question to the end. The answer to this question may be non-trivial.
Replacing a number of 2-coil latching relays with single coil latching relays to save space on the board. The trouble: single coil relays are a lot more trouble to drive with the current reversal requirement.
Currently low-side switches such as darlington arrays or mosfets are doing the work and they cost pennies. Here are the common solutions I've thought of which do not work in our case:
An array of h-bridges: Too expensive and not enough room on the pbc board.
The method shown in the picture below (from Maxim) for every relay driven by two low-side switches: The relay coil voltage is close to Vcc (3V) which yeilds low R values and a total current draw above what the PS can provide.
Capacitor Charge and discharge drive: This method requires large capacitors that are physically too large to fit in the enclosure (defeats the purpose of using single coil relays).
An array of analog switches (one per coil as an on/off switch and two to flip Vcc and Gnd and reverse pol): This might work, however analog switches with low on-resistance are expensive compared to low-side mosfet or bjt switches.
What other solutions are recommended in this case?