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Wiring/driving Si2305DS SOT-23 P-mosfets correctly
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spec:

--- Quote from: 3dgeo on January 21, 2019, 01:34:02 pm ---I would really appreciate your help. Basically my circuit is a copy from

but instead of 3 * TCL5940 I'm using 3 * TCL59116 (I2C interface), and only 15 outputs per chip with 7 P-mosfets. Originally I've designed this to run on a USB with 10mA per LED (still bright enough), so 10 mA * 45 LEDs ON at one time = 450mA. MCU is ATMEGA32U4. But I also implemented a feature – if desired free TLC output will cut TLCs IREF pins resistance to ground in half and increase LEDs current to about 20mA (total ~900mA).
This project is a macro keyboard and I probably should point out that P-mosfets outputs also are used to multiplex keyboard matrix.
--- End quote ---
Thanks for info. I will have a look at the design.
3dgeo:
I made simplifies schematic, hope this will help.
ICs (TLC59116) sinks the current (PWM) and sets constant current according to resistance from REXT pin to ground.

3dgeo:
I found that there already is 22R in the BOM, so with some effort and a lot of cursing I managed to squeeze all in   :rant:
China new year soon, so I have to hurry up with PCB prototyping or I will have to wait 3 weeks until china sobers out  ;D
Feedback?


spec:
+ 3dgeo

I have not found any radical changes to the design of the PMOS switch, except that it would be better to reduce the gate pull up resistor to 1k, so you can go ahead with the PCB procurement.

I have been looking for a PMOSFET with a higher gate threshold voltage, which would improve the turn-off performance and have found a couple of PMOSFETs, but have not completed the search yet. Will advise.
spec:
+ 3dgeo

This is the PMOSFET that I would recommend: http://www.vishay.com/docs/67401/sq3469ev.pdf

It is a TSOP pack. Hope it will fit.

Attached below is the  latest schematic for the PMOSFET switch:
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