Other Parts Discussed in Thread: DRV8704, CSD18540Q5B,
Hello TI Support,
I am working on a medical motor drive application. I am using the DRV8704 + H-Bridge (4x CSD18540Q5B) to drive a BDC motor.
Motor is battery powered 24V nominal voltage, and can draw up to 25A
In normal use case, the H-Bridge drives the motor for bi-directional control. so far so good.
Since this is a medical device, there is a requirement to provide a secondary path to drive the motor in ONE direction in the event of emergency.
Conceptually, we provide direct path from Battery to the motor for uni-directional control. Note, that the system power would be switched OFF
The problem, since the motor connects to the H-Bridge and therefore the DRV8704 AOUT1/AOUT2 pins, I need isolation
Due to system physical constraints, we can't use relays (25A). I was thinking to use the LM74700 to drive external N-CH MOSFET as per the image below
Q1) The first question, is it even possible to use LM74700 as shown above? any potential problems?
Q2) assuming it's a non issue, is it possible to use 1x LM74700 to drive 2 Nch-FETs?
In the case of normal use case, H-Bridge is Enabled, so in one direction AOUT1 is +VM and AOUT2 is GND, and in the other direction AOUT1 is GND and AOUT2 is +VM
therefore, depending on the polarity, a reverse current must pass through the FETs. I understand that LM74700 normally blocks reverse current but can be made to allow reverse current as per another thread.
the follow up question, then
Q3) Can the LM74700 be used to drive the 2-Nch FETs in this configuration? How would one connect Anode/Cathode ?
Any recommendation / solution to the above is appreciated.
Thank you
AJ