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In my design, I would like to use a constant current source pin from component A, which is normally used to drive an external LED, to activate the enable pin of another component, component B.

Here are more details:

  • Component A is a fuel gauge (datasheet : URL). It has three output pins (LEDCNTLA, LEDCNTLB, and LEDCNTLC) used to control external LEDs. According to the reference manual (URL), it is possible to activate or deactivate the LEDs by writing to a specific register via SMBus (register 0x0054, bit 17). enter image description here
  • Component B is a boost converter (datasheet : URL). The enable pin of the boost converter has a threshold of 1.5V. enter image description here
  • The diagram is as follows : enter image description here

When I enable the LED, I want the boost converter to turn on, and when I disable the LED, I want the boost converter to turn off. However, I am concerned that this may not be possible because the LED output pin is a current source rather than a standard GPIO output.

Is there a circuit that would allow me to achieve this functionality?

Thank you!

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  • \$\begingroup\$ I see you are kind of rebooting your earlier question with some newly hatched direction to consider. No extra pins required, either. \$\endgroup\$ Commented Mar 11 at 10:23
  • \$\begingroup\$ Will you have any of those LEDs populated in your design to provide a visual output to the user, or are you only interested in sending a signal over to the boost converter? \$\endgroup\$ Commented Mar 11 at 16:08
  • \$\begingroup\$ I am only interested in sending a signal over to the boost converter. The LEDs aren't necessary \$\endgroup\$ Commented Mar 12 at 8:45

1 Answer 1

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Not just a current source : it looks like the LEDs are multiplexed, so the pins will be constantly switching in a sequence depending on which LEDS should light.

Of course measuring the voltage across a resistor placed where a LED would be will produce a signal which depends on the current. But you will have to decode the voltages on each end of the resistor to work out if they would have lit the LED. Another idea would be an optocoupler with a smoothing filter on its output -light the LED in the optocoupler, the output transistor will start pulsing on and off , you filter the pulses to produce a switching signal.

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