I am designing a board with L6206 drivers for solenoids. My board is using connectors with a 3-amp per pin maximum, so I chose the 6206 for its ability to set a conservative 3 amp shutdown limit on the high side using an external resistor. Unfortunately these parts do not have over-current or short protection on the low side. What is the best, simplest way to augment the typical application circuit for protection on the low side? I am using the part initially as four separate half-bridges for driving solenoids (so the high-side current limit is split between two solenoids on each bridge), and would like to protect the chip, by deactivating the low-side switches, if the output gets shorted to a 12V supply.
Here are a couple ideas:
1. A comparator on a low-side sense resistor pulling the enable pin low alongside the high-side overcurrent shutdown pin;
2. An NPN transistor hanging off the low-side sense resistor, pulling the enable pin low
3. A chip-based solution such as the L6506
I looked at the app node Short-circuit protection on the L6201, L6202, and L6203 where the author suggested something similar to option #2, but using an SCR, and then a one-shot. These solutions probably stem from the lack of Schmitt triggers on the L6201-3. Since the L6206 has Schmitt triggers on the enable pins, I'm assuming a simple NPN tugging on the enable pin, with sense resistor chosen for 0.7V at the overcurrent level, would do the trick. I'm planning to add small inductance (10uH) to each half-bridge output to guarantee enough time for this protection to act. Is this necessary?