Thanks!
Ah cheers dude, I appreciate it :THUMBS-UP: :-) .
You are right about how the LVP works. No confusion. I have removed the MCU, so cannot test it, but should be approx 1.5V.
[quote=Barkuti] Mmmkay but how is the input current limit removed or adjusted? [/quote]
Adjusted - replace R14. See datasheet for required value. Removed - short R13 to ground.
Halfway between the min Vf and max Vf. E.g XHP70 turns on at 5.3V and reaches 6.5V at 8A. Halfway is 5.9V, so set R16 for 5.9V out from MP3431.
The datasheet gives more info on the specifics. Not sure about the H1-A, but it's a different chip...
[quote=Barkuti] Is pin 2 from the VLDO a good place to set an e-switch? [/quote]
A switch to interrupt power to ONLY the MCU would work, so yeah, between LDO out and MCU pin1. You'd need to lift the leg of the MCU though.
Cutting power to the op-amp would make the light go crazy (most likely stuck in turbo or go into overvoltage shutdown).
The integrator can have better standalone stability, but the DC/DC stage is compensated to be very stable for output voltage transients.
It uses FB to detect the output voltage, so the op-amp is just giving it lots of little adjustments, which are stabilised by the compensation network. Too much op-amp 'stability' = the MP3431 being slowed down.
You are right about the sense resistor/R6/R7, but it's easier for people to replace/solder a 1206 resistor than an 0402. And it can reduce output current power loss.
They just used it in a faster configuration. The op-amp does not need much compensating, as the MP3431 handles the power stage stability and responds very well to FB (see the bode plot in datasheet).
For my circuit, I tested the voltage gain required using LTSpice, but I will link an online equivalent HERE.
It can be seen that for eg an XHP35 needs output swing of ~11V to ~14V, setting the MP3431 to 12.5V. FB is regulated to 1.00V, so op amp needs to raise and lower FB so that 2.5V is divided into FB for an output swing of 11-14V.
Simulation shows that 1.05Vopamp = 11Vout, and 0.4Vopamp = 14Vout. So op-amp output swings 0.65V. 30mR Sense Vdrop at 2.5A = 0.075V. So op-amp gain required is 0.65/0.075 = 8.67.
That's very low in openloop, and gives the op-amp plenty of gain-bandwidth headroom.
For a given combination of PWM divider and sense resistor, yes. The only catch is that the Vf needs to be within the range set by R16.
Connected my test driver to a 6V MT-G2; it is happy to feed the poor thing up to 8A+. Lower currents no problem at all. R16 needs setting to 250/270k for the Vf though, so yeah, you need to replace one resistor (as icpart mentions).