Texas Avenger "TA" Driver series - Triple channel + Bistro or Narsil + Clicky or E-switch - The Ultimate open source driver!

Can someone tell acceptable parameters ( Qg & RDSon) of 1 FET to drive from moonlight to turbo?

QG<30nC at 4.5V (the gate charge gets bigger with more voltage, but only a part is needed to get above the threshold and the FET conductive)
RDSON 1-4mOhm

https://www.mouser.de/datasheet/2/196/Infineon-BSC009NE2LS5-DS-v02_00-EN-540021.pdf

https://www.mouser.de/datasheet/2/427/sir800adp-1484143.pdf

this MOSFET has a relative high Gate threshold voltage
https://www.mouser.de/datasheet/2/916/PSMN2R4-30YLD-1320632.pdf

Yes, i know, but you said: “High power MOSFETs are relative slow ” Are they ok for moon?

if you get at least 12 bit resolution yes otherwise no
and with temperature drift they may get unreliable or too bright without current feedback

O.K. I got it

I’ve done some research and I think you should focus on the shortest raise time and fall time than Qg and RDSon. This probably telling you how fast you can switch FET with PWM.
Not sure how much turn on and turn off time matter.
Also lowest Vgs th better.
Power dissipation probably is also parameter you would take a look at.

Seams that FETs that Lexel already pointed are one of best we can have.

Again if you don’t have a real FET gate driver that can deliver like 1-2A with about 2-3Ohms driver resistance you will never see such short raise/fall times
the gate charge is the most limiting source when driving with the little current from an Attiny MCU

Higher RDSon MOSFETs with less max current capability have smaller chip area reducing the gate charge and speed up the switching
A MOSFET has always switching and conduction losses, at our low frequency of about 20kHz the conductive losses play the major role
If you want to increase the resolution you can reduce the Moonlight PWM frequency by factor 10 to about 2kHz still having a bit more than 10 bits resolution (but you need to implement that into a firmware)

you can create a Gate driver using two small SOT532 MOSFETs (crucial here is low RDSon and enough peak current, so they don’t get blown remember most big switching MOSFETs have like 1Ohm Gate resistance making the worst case 4A peak current while charging the gate)
one N channel on the MCU and one P-channel driving the MOSFET

Then you get very fast switching time as the gate and now you need to focus on more resolution of the PWM source

Then you have then significantly increased the current ringing problem and may need additional MCU voltage stabilization adding a 2. low pass filter (most new designs have 4.7Ohm plus 10uF behind it to eliminate the spikes that can reset the MCU)

Would it be better to use a small buck driver for the first couple hundred lumens and then switch over to pwm fet?

Designed my own FET+1 driver for D10 headlamp. Circuit identical to D4, only indicator led and cap on output to reduce moon a little. I’ll go for Si4866BDY. Found it for 12 cents :slight_smile:

It would be a very efficient way but also quite costly and complex….Really the efficiency difference wouldn’t be all that big so return of investment would be fairly low.
I’d love to see it though.

this FET has no advantages electrically over the other mainly used MOSFETs, it is only cheap
high input capacitance,
Gate charge,
relative high RDSon,
bad thermal conduction to PCB

I bought recently pretty good FETs for 1 Cent price bug I can sell them here cheap

So can this firmware be used on a driver that uses a click switch that cuts the power to the batteries, so a half-press will change the modes?

Yes, that is what bistro is designed for.

For an e-switch you need something like Narsil or Anduril.

Is there a schematic available that works with Bistro? I’m trying to figure out how it works, such as if a capacitor keeps a residual charge during a half press, etc. And how the MCU remembers the last mode after remaining off for a while.

Thanks!!!

You will have to dig through the archives to find all the details on that.

But on a basic level, the OTC cap drains when power is cut and when the MCU turns back on it reads the remaining voltage. Based on that remaining voltage it decides if it is a half press or full press.

The downside to this is that it can be inconsistent, which is why a better option has been desired for some time. The idea option is to use a larger cap to keep the MCU powered for a few seconds after the light is turned off so it can measure the exact length of the button press.

Yes, there is an option for mode memory.

I’ve been looking through the archives for a couple weeks now and haven’t been able to find anything. Any clue what to search for?

A lot of the base design stuff like that was many years ago, we have just refined the ideas since then. Not sure what to search for, off time cap and OTC are ok but honestly since the design has evolved many times over the years, not sure you will find an all inclusive rundown.

The design we are using now is fairly simple to figure out though, the OTC cap is what measures the off time like I said above and the other pins are basic inputs and outputs for the different channels.

For the firmware side of things, that is another all game, it is open source if that is your thing but toykeeper and TomE are the ones that have made this work.

Hi I was trying to understand these drivers and I got lost, wanting to try which of these I can use to power an xhp70.2 led, with the possibility of ignition and charge control, I must be able to power with 2s or 3s batteries indifferently, let me know how I feel, thanks

2-3S means a Buck driver that does not use voltage difference to determine switching frequency like the LM3409 does
And charging needs also a separate circuit like TP5100, but a charging circuit can only charge one battery configuration not 2

I have build a few TA drivers successfully but three of my latest drivers seem to have a problem. If I use them on Turbo or with all 7135’s the flashlight steps down the brightness after a few seconds. One or two minutes later the flashlight will turn off completely.

It could be the driver is overheating with the AMCs but other drivers don’t have this problem. What could be the cause of this sudden stepdown and how can I resolve it? Any suggestions would be appreciated.