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TS5A623157 - VIH threshold discrepancy

Wabri
Prodigy 35 points
Other Parts Discussed in Thread: TS5A623157, TS5A23159, TS5A23157

Need to power a TS5A623157 switch (or similar) with a V+ of 3.3 volt, but drive it with 1.8 volt logic:

1. Table on page 5 says "Input logic high VIH min. V+x0.7", which means 2.3 volts for a V+ of 3.3 volt - definitely much too high for 1.8 volt logic.

2. Figure 8 on page 14 "Logic-Level Threshold" is a diagram showing both VIH and VIL being about 1.4 volts for a V+ of 3.3 volts - quite comfortable for 1.8 volt logic.

I'm puzzled about the contradiction of these two statements, so how to proceed? Would some user or TI engineer with more insight explain that to me, please? - Thanks.

  • 0
    Expert 2400 points

    Hi,

    On page 5 you have got the minimum/maximum values. These values are guaranteed over the complete temperature range. The figure 8 on page 14 shows just typical values.

    Best regards,
    Edwin Krasser

  • 0 in reply to Edwin Krasser
    Prodigy 35 points

    Please have a look at the similar TS5A23159 instead. On page 13, you'll find figure 9, an absolutely identically-looking "Logic-Level Threshold" diagram when compared to figure 8 on the TS5A623157 datasheet mentioned above.

    What surprizes me: the values from the associated TS5A23159 table (pg.6) read "Input logic high VIH Full 2 5.5 V" here. Same holds for the 5 volt spec (pg. 4): "Input logic high VIH Full 2.4 5.5 V. I see that both switches (i.e.TS5A623157 and TS5A23159) share the same Threshold diagram, but there's no such contradiction in the context of the TS5A23159 datasheet - table and diagram match nicely here.

    Why not simply designing-in the flawless TS5A23159 instead? -  It's Ron is much lower, and so the associated capacitances are much higher - unusable for my application.

    Next surprize: have a look at the TS5A23157 - a sibling closely related the TS5A623157. Once again, there is the "VIH min. V+x0.7" spec in the datasheet table. But there's NO misleading "Logic-Level Threshold" diagram in this datasheet, so, again, there's no contradiction. In this case, I'll take the V+0.7 for granted.

    To me, the contradiction in the TS5A623157 datasheet (and only there) looks like a copy-and-paste slip of the datasheet author.