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PSoC 5, 3 & 1 MCU

Anonymous
Not applicable

Hi all,

I'm confused regarding how much current 5LP GPIO pins can drive; any help is appreciated.

Here's where I get confused:

  • The CY8CKIT-059's "User LED BLUE" is a LTST-C170TBKT from Lite-On Inc. 

  • This LED has a DC Forward Current of 20 mA, according to its data sheet. 

  • On the CY8CKIT-059, this LED is driven by P2_1 (via a 820 ohm resister), according to the CY8CKIT-059's schematics.
  • AN72382, § 2.4 states "In general, [PSOC 5LP] GPIO pins can source 4 mA."

  • If the GPIO pins can only source 4 mA (unless ganged), then how can P2_1 drive enough current to light "User LED BLUE" if that LED has a DC Forward Current of 20 mA?

What am I missing here?

I'm sure it is something really obvious.

Thanks in advance,

-Chris

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Contributor II

20mA is an absolute maximum rating for that LED.  You don't need to send 20mA, you can send less, it'll just be dimmer than if it was running at a full 20mA.

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1 Reply
Contributor II

20mA is an absolute maximum rating for that LED.  You don't need to send 20mA, you can send less, it'll just be dimmer than if it was running at a full 20mA.

View solution in original post

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