Other Parts Discussed in Thread: DRV110
I have a question regarding the latch in TIDA-00289, specifically how the plunger movement detection circuit resets.
Much treatment is given to the operation of the plunger detection circuit based on back EMF and this is straightforward and well detailed. However, if a controller/PLC is expected to cycle a solenoid repetitively, the plunger motion detection latch (U3 in TIDU578 Figure 48) must somehow reset in order to be useful in detecting plunger motion in subsequent operational cycles.
It is described in section 2 of TIDU578 that the system is to activate from an Enable signal supplied by a PLC or controller. As described subsequently, such an external controller/PLC would supply an activation signal to the EN input of the DRV110 and the circuit would operate as described. Because the DRV110 (U4) is assuredly intended to serve as the controlling device, in an industrial application it would seem the circuit would be powered on continuously, and only the Enable signal would be toggled to activate and deactivate the solenoid. It does not seem the intent of the designers for the entire circuit to need to be de-powered to reset the plunger detection circuitry for subsequent operations of the solenoid, however I can see no other way for the latch (U3, D8, R39) to be reset.
As far as I can tell, when the controller/PLC de-asserts the activation signal connected to the EN pin of the DRV110, the PWM activation of Q4 will cease, and the solenoid will no longer be energized, and its physical plunger would being returned to its "off" position by a spring or gravity, etc. For subsequent cycling of the EN signal, although the DRV110 may operate normally the ITRIP signal appears it may remain latched from the previous operation. I expect I may not fully understand the Solenoid Plunger Position Detection Circuit (Figure 16 in TIDU578), can someone please walk through how the latch resets?
Many thanks,
Charles "Casey" Goodwin
