CC2640: Driving led by GPIO directly or not?

Antimatter

Part Number: CC2640
Other Parts Discussed in Thread: TIDA-00756

I noticed in some TI reference designs (e.g. http://www.ti.com/tool/TIDA-00756) LED's are directly driven by the GPIO with only a resistor to control the maximum current.

The GPIO pins of the leds in this design have the setup:

Board_RED_LED    | PIN_GPIO_OUTPUT_EN | PIN_GPIO_LOW   | PIN_PUSHPULL | PIN_DRVSTR_MAX,	/* Red LED	 */
Board_YELLOW_LED | PIN_GPIO_OUTPUT_EN | PIN_GPIO_LOW   | PIN_PUSHPULL | PIN_DRVSTR_MAX,	/* Yellow LED	 */

For an ultra low power design what's the best option to control a LED, directly connected to the GPIO or using a MOSFET?

What's the leakage current of the LED pins in off state of this reference design?

Thanks.

over 7 years ago

0 Eirik V over 7 years ago

TI__Guru 56590 points

Hello Antimatter,
You can disable the output buffer on the IO's on CC26xx to avoid any leakage current. Refer to the PIN_setOutputEnable function in the pin driver.

0 Antimatter over 7 years ago in reply to Eirik V

Intellectual 430 points

Hi Eirik,

OK, good to know. Regardless the output mode (tristated, push-pull, open drain, open source) there is no leakage if the output buffer is disabled?

Sorry, I'm not an expert, but when to use the PIN_PUSHPULL option? What does it exactly do?

Thanks,
Peter

0 Eirik V over 7 years ago in reply to Antimatter

TI__Guru 56590 points

Hello Anti,
Under normal operating conditions there should be no leakage if both the output buffer and the input buffer is disabled. The push pull refer to standard output topology (drive high or drive low).

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CC2640: Driving led by GPIO directly or not?