I'm trying to drive a solenoid to create a magnetic field. I've got a constant current controller circuit that supplies the current I need, but I'd like to control this using an H-Bridge so the the polarity can be changed and/or the coil can be turned off quickly. (<1ms)
I'd been planning to do this with an IC H-bridge, but am running into problems. Typical currents for my application are ~10-300mA which can require voltages of 5mV or less. The current controller is capable of supplying this and regulating itself, however the H-briges I've seen can't operate at such low voltages.
For instance, the SN754410's datasheet says:
The SN754410 is a quadruple high-current half-H driver designed to provide bidirectional drive currents up to 1 A at voltages from 4.5 V to 36 V. The device is designed to drive inductive loads such as relays, solenoids, dc and bipolar stepping motors, as well as other high-current/high-voltage loads in positive-supply applications.
The SN754410 has seperate supply pins for the logic circuits and for the outputs but the lowest recommended voltage I can find for the supply of an H-bridge is around 4.5V.
How can I quickly turn on/off a solenoid that only requires mVs and mAs?