Can I Use CAT4101 with Arduino to PWM High Brightness LEDs in Parallel?

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In summary: If you want to drive more LEDs, you need to add a transistor. A voltage divider will work too, but a transistor is more efficient.
  • #1
Hi all,

I'm trying to PWM a high brightness LEDs in parallel ( and I was hoping to use an Arduino and a CAT4101 driver ( I was hoping that someone could tell me if this would work or not, or if there's something I need to add to the circuit.

The LED has about a 3 V forward voltage, and so I'm wondering if I can use the 0-5V PWM pins of the Arduino to drive it using the CAT4101 with a 3V power supply. I've uploaded a sample schematic here.

Thanks for any help

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  • #2
I've never used the parts, so this is just opinion from the data sheet.

1. 3V isn't enough since the part needs 0.5V headroom (maybe a little less at only 50ma) and the LED has a 3V drop. That means 3.5V at an absolute minimum. Do you understand how a constant current driver works?

2. If you want it to light up you need to add an rset resistor to ground. 50/400 = 125uA so at 1.2V that gives 9.6 Kohms to get 50ma. Also, above 150ma will damage the LED, so be careful with rset. The LED really wants to run at 50ma..

3. The data sheet does not really address what happens if EN goes above Vin. Since all pins are OK to 6V absolute maximum, then maybe nothing. But, you may want to limit the voltage at EN to 3V. This is easily done a number of ways. A transistor, a voltage divider, or possibly just a 10K series resistor to limit the current in case there are internal ESD clamp devices.

Usually when there is a voltage sensitivity the spec will be Vin+0.3V as the pin max. Since that isn't there, there may be no problem, but a series 10K resistor on EN will cause no problems.

Not sure why you aren't just running it from a 5V supply, same as the arduino. It's function is to control the LED current from a higher voltage supply. With 5V you have 3V across the LED and 2V across the driver, which is pretty decent.
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  • #3
Ok, thanks for your input. Would you be able to draw a small schematic on how to use a 5V power supply? I was using a smaller version of the Arduino so I figured less voltage would be better, but maybe I can do 5V. I'm only vaguely familiar with how a constant current driver works. Do you mean that I need to put a resistor from the reset pin on the driver to ground?

I found this source. Basically I just want to do the same thing, but I don't need to drive as many LEDs, so I dont' think I need the TLC5940.,20675.0.html

Do you think I can follow the same schematic?

Thanks again
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  • #4
1. rset is not a reset. It is R set which is a resistor that sets the current through the LED. That current will flow no matter what voltage you supply (within limits). If you just replace 3V with 5V and add 9.6K to ground on rset, you are done.

2. I just noticed that your LED is hooked up completely wrong. Look at the data sheet again. Just do Figure 1 (same as the Arduino forum picture) with 9.6K rset. The 5V supply supplies 5V to the LED and VIN, and the LED pin sinks 50ma if rset is 9.6K.
  • #5

I would recommend consulting the datasheet for the CAT4101 to ensure that it is compatible with the Arduino and the LED you are using. It is important to check the voltage and current requirements of all components to ensure they are within the specifications of the CAT4101. Additionally, it may be helpful to simulate the circuit using software such as LTspice to see how the components will behave together. If you have any doubts or concerns, it may be beneficial to seek advice from a professional in the field or conduct further research.

Related to Can I Use CAT4101 with Arduino to PWM High Brightness LEDs in Parallel?

1. How do I connect the CAT4101 to my Arduino?

To connect the CAT4101 to your Arduino, you will need to connect the VCC pin to the 5V pin on your Arduino, the GND pin to the GND pin on your Arduino, and the OUT pin to the desired output pin on your Arduino. You can also connect the DIM pin to a PWM pin on your Arduino for dimming control.

2. Can I use the CAT4101 with any type of LED?

Yes, the CAT4101 can be used with a variety of LEDs including single color, RGB, and high power LEDs. It can also handle a wide range of LED voltages and currents.

3. How do I control the brightness of my LED with the CAT4101?

You can control the brightness of your LED by adjusting the PWM signal sent from your Arduino to the DIM pin on the CAT4101. This will adjust the current flow through the LED, thus changing its brightness.

4. Can I use multiple CAT4101s with one Arduino?

Yes, you can use multiple CAT4101s with one Arduino by connecting each VCC and GND pin to the corresponding pins on the Arduino, and connecting each OUT pin to a different output pin on the Arduino. You can also use one PWM pin on the Arduino to control the DIM pin on all the CAT4101s.

5. What is the maximum output current of the CAT4101?

The maximum output current of the CAT4101 is 1.5 amps. It also has built-in overcurrent protection to prevent damage to the LED or the IC.

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