------Question for SI8231AB-D-IS Please Put your question below------
I am designing a circuit using a GaNFET with a fall time of 7.5ns, driven by a SI8231AB-D-IS driver. I’m trying to evaluate the programmable DT pin.
On the data sheet it provides RDT=6Kohms → 70ns and RDT=100Kohms -->900ns. It also mentions that tying DT to VDDI gives about 400ps.
My question: is the 6Kohm and 100Kohms the only specified range for RDT, or can I safely use an RDT below 6Kohms to achieve a dead time in the tens-of-nanoseconds.
Thank you,
Jake
Greetings,
The dead time equation given in section 2.7 (p.17) of the datasheet is subject to a degree of imprecision. I wouldn’t read too much into the specific choice of 6K and 100K as discrete points within the usable range (<220K per footnote p.23) for characterization; picking two discrete points to characterize/guarantee/test is a lot more practical than doing the entire continuum, and to pick those points roughly a third-ish from either end is a lot more informative than two points in close proximity.
Likely more significant is the range of variability at those two points, which looks to push into +/- 30% territory; try to tune things too finely during development and one’s liable to get burned in production. (pun intended…)
So if the datasheet indicates that there’s a 400ps default dead time with the DT pin floating/pulled high, but increasing RDT to ground extends dead time, one can infer that there’s some sort of logic function that kicks in somewhere above 220K that abruptly changes a programmed 2.2us dead time to a 400ps one. At the lower end I wouldn’t really expect the default to be abrogated by shorting the program pin to ground, but think it entirely reasonable to aim for a dead time in the 10s of nanosecond range.
