Hi experts,
How to understand the spec "output resistance high" in datasheet? It is 43R in datasheet, in this way, the max pull up driver capability will be 14V/43R=0.32A, it is much lower than 4A.
For other vendor's 4A driver, for example, MAX5054, this parameter is much lower, it is 5.5R. Could you please help to explain why UCC27324-Q1 has so large output resistance? Thank you.
Hello Arie,
I believe the main reason for this difference is the output structure of the two drivers. The UCC27324 has MOSFETs in parallel with BJTs. The output resistance is calculated by running a small DC current through the output stage and measuring the voltage drop across it. See the third point in the picture you posted. 
As you can see in the image you posted, the voltage drop on the high section is 300mV compared to the 22mV typical on low. I believe this is because the VCE drop on the BJT is quite high with such a low Ic current. Here is another driver with a similar output structure, as you can see it also has a much higher pullup resistance than pulldown, much like the UCC27324. The Maxim device seems to use a different output structure and test condition, so the comparison is a bit difficult. In short, the output stage is not simply resistive, so there are some limitations to the calculation we are making. Ultimately, the part can still source 4A as advertised, but it may be harder to calculate the exact peak source current as you showed in your post. Hopefully this was helpful.
thanks,
Alex Mazany
