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My Arduino Pro Micro can source 500mA from 3.3V VCC, when it is USB powered.

The chip itself, is rated for 200mA, though, and its output pins for 20mA recommended, 40mA max.

I am looking to have 3 PWM outputs, though, each doing 120mA. The combined 360mA would be in-spec for VCC, but not for the chip.

Is there a buffer IC that I can use that will switch these loads at that current, and can keep up with a few hundred Hz PWM?

From what I've read, you can switch loads with discrete transistors, but these require extra components like resistors? Are there CMOS chips that will take the PWM signal and output it at 120mA?

I am looking to source the current, not sink it.

The load in my application are LEDs driven with constant-current drivers that are daisy chained. I just want to PWM the Vled supply so I can dim per channel, of the entire daisy chain.

UPDATE: I went with @Majenko's solution of pre-biased DTB114EK. Although it somewhat works, it seems to struggle to deliver 30mA out, even though it is rated at 500mA?

UPDATE: The DTB113ZC works better. Due to a lower bias resistor, I can get more current through it.

Bram
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  • @gbg that datasheet seems to indicate it needs 4.5V to operate? My Arduino runs with 3.3V as VCC. Also, 2A per channel is far more than I need? – Bram Oct 10 '21 at 21:40
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    Wait, what kind of load do you have? RGB LED, I presume? – gbg Oct 10 '21 at 21:48
  • @gbg It is complicated. I drive LEDs with a TLC5928 but I want to dim them per channel, by modulating Vled. I now there is the TLC5940 option, but I want to stick with the 5928. So the load is a led, hooked up to a constant current driver. I'll add a link to my application. – Bram Oct 10 '21 at 21:56
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    You can get pre-biased transistors that don't need resistors, such as the [DTB114ECHZG](https://www.farnell.com/datasheets/2311868.pdf). – Majenko Oct 10 '21 at 21:59
  • @Majenko Thanks! That looks interesting. So I would hook my PWM output to the base, my VCC to emitter and the load to the collector? Also it mentions 'invertor.' Does that mean that I need to reverse my duty cycle? – Bram Oct 10 '21 at 22:09
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    That's correct. You pull the base LOW to turn the output ON. You could add an NPN (or n-FET) to invert it for you if you wanted but that's more components... – Majenko Oct 10 '21 at 22:10
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    How about the ULN2003? – gbg Oct 10 '21 at 22:37
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    @gbg They sink current, not source it. – Majenko Oct 11 '21 at 00:16
  • I used this module https://wiki.seeedstudio.com/Grove-MOSFET/ – Juraj Oct 11 '21 at 09:03
  • Use a transistor. [Here is an example schematic and calculations I did for an NPN BJT transistor](https://arduino.stackexchange.com/a/77602/7727). You can learn how to do the math and process yourself following my answer. – Gabriel Staples Nov 22 '21 at 08:43

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Here is a part that will do the job for you, just 4 wires to connect. Use your favorite search engine or go to your favorite china supplier and use this term: "Low Control High Voltage 12V 24V 36V switch Mosfet Module For Arduino Connect IO MCU PWM Control Motor Speed 3V 5V". You will get many choices several in the dollar range. It is opto isolated so that eliminates the ground connections etc. I have used them several times and they work nicely. enter image description here

Gil
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