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Which diode specifications for equivalence?
Which diode specifications for equivalence?
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Old 23rd August 2014, 11:46 PM   #11
brucew268 is offline brucew268  United Kingdom
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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
brucew268 is offline brucew268  United Kingdom
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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
brucew268 is offline brucew268  United Kingdom
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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
Mark Johnson is offline Mark Johnson  United States
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Which diode specifications for equivalence?
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, 109 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
Terry Given is offline Terry Given  New Zealand
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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
Mark Johnson is offline Mark Johnson  United States
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Which diode specifications for equivalence?
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, 120 views)
File Type: png PR_300_amps.png (58.9 KB, 102 views)
File Type: png 10A05_600_amps.png (50.1 KB, 102 views)

Last edited by Mark Johnson; 11th September 2014 at 01:01 PM. Reason: adjust images
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Old 7th August 2017, 10:24 PM   #17
Karl vd Berg is offline Karl vd Berg
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Excellent thread!!
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Old 7th August 2017, 11:17 PM   #18
Chris Daly is offline Chris Daly  Australia
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Quote:
Originally Posted by brucew268 View Post
I'm looking for equivalent diodes for 1N4003's used in a power supply, but having difficulty identifying which specs are relevant and which are not. For example the
1N4003 gives: Vpeakrev=200, Vrevrms=140, CurAve=1.0A, CurPeak=30, FwdVolt=1.0V.
Schottky11DQ09 gives: Vpeakrev=90, Vrevrms=?, CurAve=1.0A, CurPeak=30, FwdVoltDrop=0.68-0.96V.
Some Hexfreds give a FwdVoltage drop of 2.2V and CurAve=25A others 15A.

I'm not sure which measures are relevant to my application and which are not. (I'm not designing a circuit, just trying to consider what would be good equivalent replacements.)

You can reference my power supply schematic if that helps (attached).
I would tend to stick with 1N4003, as the 78X 79x are not going to be any better, although they work, they are miserable for audio related circuits.

A really imaginative circuit would see the LT4320 with some N channel Hexfets and followed by mosfet cascode regulators.

Last edited by Chris Daly; 7th August 2017 at 11:20 PM.
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