ULN2801 to drive 3.3V GPIOs

[mahenreddy]

3.3v darlington array

Attached the snapshot of ULN280x datasheet. I think I need to use ULN2801 (without base series resistor) as my GPIOs are 3.3V Vdd logic and can source only 2 ma from each GPIO. The Voh and Vol for the GPIOs are 2.66 min and 0.66 max respectively. Will my MCU GPIOs able to drive the ULN2801 which inturn are connected to the relays.

https://www.st.com/stonline/products/literature/ds/1536.pdf is the link to full datasheet of ULN280x.

Is ULN2801 suitable for the 3.3V GPIOs?

Also help me understand the calculation of base current / voltage required to switch on the Darlington array of ULN280x from the datasheet. For example how did they come up with Ii (ON) of 0.35ma typ and 0.5max for ULN2804A at Vi = 5V?

Thanks

 

[FvM]

darlington array 3v3

I think I need to use ULN2801 (without base series resistor)

You shouldn't, if you don't want to damage the CPU I/Os. 2803 is still fine at 3.3V voltage node, as the datasheet clarifies.