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Old 23rd August 2014, 11:46 PM   #11
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LOL! Guitar = forward. I was curious about the basis for 'Forward voltage drop' and 'Reverse voltage'
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Old 31st August 2014, 03:45 PM   #12
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Lots of good help here. Thank you. BTW: HexFred does seem to be a possible option for an existing PCB using the TO-247 package. The lead spacing is about 11mm and lead width is said to be 0.99mm. (The diode holes on my PCB are 1.0mm, 11mm apart.)

For example Vishay's HFA15PB60PBF or HFA25PB60PBF.

...or I may just stick with the Schottky 11DQ10's.
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Old 6th September 2014, 05:30 PM   #13
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Oh well, you risk 12 and sometimes you lose. I ordered the HexFred HFA15PB60PBF and found that the lead is 1.21mm x 0.69mm, larger than indicated in the datasheet, and won't fit in my 1.0mm holes. No big deal I guess; I'll stick with my Schottky.
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Old 6th September 2014, 05:46 PM   #14
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I took a look at the datasheet and found this drawing on page 6.

It appears to say that the lead width (which I will call "W") and the lead thickness (which I will call "T") are permitted to fall anywhere in the min/max range:
  • 1.00 mm < W < 1.40 mm {red}
  • 0.40 mm < T < 0.80 mm {green}
Thus a skeptical/pessimistic/conservative engineer {choose your own adjective} would prepare to receive parts with W=1.3999 mm and T= 0.7999 mm.

Good old Pythagoras tells us that the required hole diameter is sqrt(W^2 + T^2) = 1.612 mm, after plating.

_
Attached Images
File Type: png datasheet_p6.png (38.7 KB, 41 views)

Last edited by Mark Johnson; 6th September 2014 at 05:49 PM. Reason: exponent fiddling
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Old 11th September 2014, 05:49 AM   #15
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I got all of the engineers at work last week with this question:

which has the highest current rating: 1N5408 (3A) or STTH16L06 (20A or so).

the obvious answer (STTH) of course is exactly wrong if you look at i_FSM - the single half-cycle surge current rating. the huge dual fast diode has i_FSM = 120A whereas the 1N5408 has i_FSM = 200A.

sure one is spec'd at 50H the other 60Hz but a quick bit of maths shows that aint even close to the difference. especially when one considers the continuous current rating.

THIS is why a 1N5408 is so often spec'd as a boost converter bypass diode in boost PFC circuits. i havent looked in a while, but istr SiC schottkies are even crappier wrt i_FSM

and boy was this hard to explain to folks with ESL. even with the two datasheeets, many folks didnt believe me.

apparently all that super fast stuff comes at a cost....

TANSTAAFL
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Old 11th September 2014, 12:57 PM   #16
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Diodes Inc. provides a nice table that shows the current "surge" (I_FSM) ratings for several different diode types:

Click the image to open in full size.

Their website also lets you sort by I_FSM. This revealed a fairly low-cost "fast" diode rated for 300 amps surge: the PR6004:

Click the image to open in full size.

The sort feature also turned up the 10A04, which is a standard slow diode like the 1N5404, but rated for 600 amps surge:

Click the image to open in full size.
Attached Images
File Type: png diodes_inc_table.png (105.5 KB, 53 views)
File Type: png PR_300_amps.png (58.9 KB, 29 views)
File Type: png 10A05_600_amps.png (50.1 KB, 29 views)

Last edited by Mark Johnson; 11th September 2014 at 01:01 PM. Reason: adjust images
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