Other Parts Discussed in Thread: TINA-TI, TL431LI
Hello,
I've played around with this and haven't come up with a good solution yet. I have a project that is battery powered (nominal 12V - 24V) but when the battery is removed I want to discharge all the caps on the board. I figured out that I need the LMV431 because of its wider Vin range and lower current requirements, but not sure how to connect it. I want this circuit to kick in when the rail voltage gets below 5V, and discharge through a 100 ohm resistor.
I've tried to use TINA-TI and did my best. See attached image. Will this work?
Shunt voltage will be set with Rtop/Rbot = 10k/10k which gives me a reference voltage of 5V.
Iref needs to be at least 0.5uA; current through Rbot+Rtop (20k total) at 5V is 250uA so that should be good. I used 100k in the simulation just to see.
Cathode current for LMV431 must be at least 100uA. At 3V, R=30k; at 24V, R=240k. So for no we will use 10k to set cathode current at minimum of 300uA at 3V or 2.4mA at 24V.
Error of 10% on voltage threshold is fine. Temperature range of the product is -10C to 40C.
Question: will this work? Is there an easier way to do this?
Question: What is the highest value of Rtop & Rbot that I can use to meet the minimum Iref for the TL431LI? These resistors are going to drain current continually so I want to minimize that current.
Thanks,
Derek