Other Parts Discussed in Thread: LM5109, , UCC27712, LM5109B
Hi I'm planning on using the LM5109A to drive a couple of low Rdson MOSFETs. The two MOSFETs are configured to drive a solenoid from automotive voltages. Solenoid manufacturer claims 200 Hz PWM frequency should work to drive it. Drive voltage at 13.8V, Vdd of the LM5109 = 12V. So HB would like to be at 25.8V right?
The question is, will this part work with such a low frequency? What is the lowest drive frequency a person could use and still guarantee that the Cboot capacitor (1 uF per my calculations) would still hold HB up?
Would it work to toggle the gate driver at 20 kHz for a bit just to charge Cboot? If this is a good idea (and it probably isn't), then how long could you expect that high side MOSFET to stay on before parasitics allow that gate voltage to drop far enough to let the MOSFET turn back off?
MOSFET has 2 ohms gate resistance and 25nC of total gate charge.
The gate-source leakage current is 100nA (maybe this answers that last question 2).
Thanks!!