TPLD1201: What is the output impedance?

Hi Kei,

Here's an FAQ describing how to calculate output impedance from VOH.

https://e2e.ti.com/support/logic-group/logic/f/logic-forum/742466/faq-what-is-the-output-voltage-voh-or-vol-when-the-output-current-is-x-or-the-supply-voltage-is-y

I've taken the liberty of performing the calculations for you the highlighted case.

RoutH= (Vcc-VOH)/IOH = (1.8 - 1.78)/100e-6 = 200 ohms.

RoutL = VOL/IOL = 0.005/100e-6 = 50 ohms

Note that this is only for the specific case of operating at IOH/IOL = 100 uA. Operating at a different current would change the resistance. Also note that this is from worst case operating conditions with margin for error, and the real Rout is likely significantly lower.

The 2X output options can sink/source more current operating at the same VOH/VOL level. This would result in a decreased output resistance.

Best,

Ian

Hi Kei,

The maximum DC current increases from 12 mA per pin for a 1x to to 17 mA per pin for a 2X.

Using the calculations I linked yesterday, we can see that for VCC = 1.8V, moving from 1X to 2X halves the RoutH to 100 ohms and the RoutL to 25 Ohms.

Best,

Ian