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LM5105 with 50ns dead time

Intellectual 2430 points

Replies: 3

Views: 325

Hi

my customer wants to reach 50ns dead time on LM5105 / LM5102.

our D/S says that deadtime can be adjusted from 100ns to 600ns which seems to tell that 50ns is not achievable

BUT

it also says that one can use 5kOhm RDT, which implies deadtime < 80ns because 80ns typ is achieved with 10kOhm.

What shall the customer expect with 5kOhm RDT? (or can they reach 50ns deadtime with LM5105 / LM5102?)

exerpt from LM5105 D/S:

page5:

DT1, DT2 Dead-Time LO OFF to HO ON & HO OFF to LO ON  ///  RDT = 10k  ///   80 ns

page10:

Operational Notes

The LM5105 is a single PWM input Gate Driver with Enable that offers a programmable dead-time. The deadtime

is set with a resistor at the RDT pin and can be adjusted from 100ns to 600ns. The wide dead-time

programming range provides the flexibility to optimize drive signal timing for a wide range of MOSFETS and

applications.

The RDT pin is biased at 3V and current limited to 1 mA maximum programming current. The time delay

generator will accommodate resistor values from 5k to 100k with a dead-time time that is proportional to the RDT

resistance. Grounding the RDT pin programs the LM5105 to drive both outputs with minimum dead-time.

thanks!

3 Replies

  • Hi Sebastien,

    Actually, the value of RT resistance below 5k is not recommand because the delay time curve is non-linear and the dealy time will be unpredictable when RT<5k, please refer to Figure 13 on LM5102 DS, the delay time seems around 50ns with RT short to ground, maybe it can be usd as a reference for minimum dead time.

    Thanks
    Oliver
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  • In reply to Oliver Pan91:

    Oliver,

    LM5105 datasheet has slightly different curves vs LM5102:
    figure14 shows dead time vs RDT, but there is nothing below 10k RDT (even though it is also mentioned in the section "operational notes" page 10 that 5k RDT is acceptable)

    Can you please just confirm that using 5k RDT is ok despite figure14 does not show anything below 10k?

    thanks
  • In reply to Sebastien Lefebvre:

    HI Sebastien,

    Sorry about the delay...
    Yes, you can using 5k RDT even though the dead time curve does not show the value. The problem is there is no data here so I can't tell you what is the exact deadtime in specific RDT below 10k. But I think it will just similar to LM5102.

    Thanks
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