PSoC 5, 3 & 1 MCU

[Anonymous]

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

[KyTr_1955226 · Accepted solution]

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.