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Old 11th May 2019, 03:39 PM   #141
prasi is offline prasi  India
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LT4320 based active rectifier
Hello Nattawa,
I have it presently at 1.2mm. and as can be seen from the layout, there is no space to put another set of vias of 1.8mm unless I increase the size of board vertically; this may not be ideal from other user's perspective. let us have some opinions.
regards
Prasi
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Old 11th May 2019, 04:56 PM   #142
RainfallSky is offline RainfallSky  Russian Federation
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Quote:
Originally Posted by prasi View Post
I am almost done with layout and here is the panel.

I plan to place order for PCB by this Friday with final quantity.

Regards
Prasi
Prasi, are SMD PCB PowerPAK SO-8 compatible?
Is a FET like this a good candidate?
SIRA50DP-T1-RE3 Vishay / Siliconix | Mouser
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Old 11th May 2019, 05:00 PM   #143
nattawa is offline nattawa  Canada
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Quote:
Originally Posted by prasi View Post
Hello Nattawa,
I have it presently at 1.2mm. and as can be seen from the layout, there is no space to put another set of vias of 1.8mm unless I increase the size of board vertically; this may not be ideal from other user's perspective. let us have some opinions.
regards
Prasi
the additional holes don't have to line up, and there is no need of increasing the PCB size. Please see attached sketch. To recover the lost copper plane area, if concerned, Rs can rotate 90 CCW and tie to pin-1 of LT4320 instead of the small via in the current layout. Cx could then be shifted to the right slightly for best copper flooding area. Just a thought.
Attached Images
File Type: png 4-MORE-HOLES.png (127.2 KB, 580 views)
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Old 11th May 2019, 05:17 PM   #144
Lo_Tse is offline Lo_Tse  Canada
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Quote:
Originally Posted by Vunce View Post
Hello Active bridge builders,

I was running some numbers to see if it would be worth a bulk purchase from the USA and then distribute to buyers.
The shipping cost is based on USPS international flat rate padded envelope.
Canada as an example will cost $25USD plus the envelope to ship.

This is the price breakdown of part# LT4320IN8#PBF from Mouser:
1 - $8.84
25 - $5.87
100 - $4.85

With these numbers as an example you would have to buy 6 units at $4.85 plus shipping to equal buying 6 units direct from Mouser.
If you bought 10 units @ $4.85 versus full price you save $15.
I think you would have to buy more than 14 to see significant savings.
It is strange. When I looked up Mouser.com US site, the price for 100 is 5.81 us$
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Old 11th May 2019, 05:20 PM   #145
Lo_Tse is offline Lo_Tse  Canada
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Quote:
Originally Posted by RainfallSky View Post
I see different prices.
I guess Mouser include tax and shipping depending on region.
My prices at Mouser are:
1 - $14.78
25 - $9.82
100 - $8.12
These numbers are very similar to those I saw at Mouser.ca (Canada) in Canadian $
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Old 11th May 2019, 05:47 PM   #146
prasi is offline prasi  India
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LT4320 based active rectifier
Quote:
Originally Posted by RainfallSky View Post
Prasi, are SMD PCB PowerPAK SO-8 compatible?
Is a FET like this a good candidate?
SIRA50DP-T1-RE3 Vishay / Siliconix | Mouser
Wow! thats an amazing FET as far as Rdson is concerned. Yes, SMD version is compatible with the linked FET.
Some hints while choosing the mosfet.
1. highest Vds (depending upon your voltage application)
2. Lowest RDS(on)
3. Highest Vgs(th) (2V min!)
4. Lowest total gate charge Qg.

I will shortly share the schematic here with suggestive options of FET that I could find. One is free to choose his own fet depending upon availability, pricing, PCB compatible package , etc as long as above mentioned facts are taken care .

regards
Prasi
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Last edited by prasi; 11th May 2019 at 05:49 PM.
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Old 11th May 2019, 06:40 PM   #147
jean-paul is offline jean-paul  Netherlands
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Hi Prasi, some questions/requests although I am very aware that changes only add up to the work you do. Still, better a 99% perfect design than a 98% perfect design

THT version: can C1 and C4 moved a bit closer to C2 and C3 (THT version). Then there is somewhat more clearance for the PCB mount AMP spade connectors.

SMD version: can the LED and its series resistor on the SMD PCB be skipped and the required 10 uF electrolytic output cap added? There are enough power LED's in PSU's already after the regulators (in general). The 10 F cap is more needed than a LED IMHO. The LED is also not on the THT board. Or: add pads for the 10 F cap where the series resistor for the LED is. The suggested way in post #45 of soldering the 10 F cap to the SMD capacitor is not good practice I think.

* I do not see the point of adding 1.8 mm holes as soldering power wiring straight to PCB's is a no no anyway according most countries regulations. The SMD version is clearly meant to replace various through hole diode bridges in existing designs so using pins to make it SIP compatible is fine. As the SMD PCB has no mounting holes soldering power wiring to a floating PCB is asking for trouble/technically undesired situations. One has the choice of using the THT version which has both mounting holes and larger pads. More sturdy, safer and more fit for the purpose.
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Last edited by jean-paul; 11th May 2019 at 06:58 PM.
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Old 11th May 2019, 08:36 PM   #148
prasi is offline prasi  India
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LT4320 based active rectifier
Hello JP,
Thanks for your comments. Yes, I too believe 99% is way better than 98%.

THT: Here is revised version of THT. I have spaced the electro further way from faston tabs. Additionally added optional 10mm pitch spacing for 1 uF cap.

SMD: Although not very clear from the 3D model, there are pads just to the right of text C2 and just above the text C1 in image of post # 45. This is where it is intended to solder the 10uF electro.
However this will require kinking of cap's leads by the builder to create a pitch of 7.5mm. Made to stand above the board like a flag.
Since the weight of cap would be approx. 0.5gm only, I thought this would not create any problems.

To Nattawa,
The point JP is making is correct regarding safe mounting of SMD board. I tried it , vias still eat too much into copper even if i keep thin pads with 1.8mm dia. Here is how it looks.
Attached Images
File Type: png LT4320-TO220-THT-LAY.png (36.1 KB, 547 views)
File Type: png new lt toshiba.png (25.4 KB, 548 views)
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Old 12th May 2019, 02:05 AM   #149
Lo_Tse is offline Lo_Tse  Canada
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Quote:
Originally Posted by Vunce View Post
Hello Active bridge builders,

I was running some numbers to see if it would be worth a bulk purchase from the USA and then distribute to buyers.
The shipping cost is based on USPS international flat rate padded envelope.
Canada as an example will cost $25USD plus the envelope to ship.

This is the price breakdown of part# LT4320IN8#PBF from Mouser:
1 - $8.84
25 - $5.87
100 - $4.85

With these numbers as an example you would have to buy 6 units at $4.85 plus shipping to equal buying 6 units direct from Mouser.
If you bought 10 units @ $4.85 versus full price you save $15.
I think you would have to buy more than 14 to see significant savings.
Your info confirmed my hunch. The shipping costs from US to other countries are not cheap, which erase the benefit of buying the chips in bulk in US

To make the GB work, I think it would have to be conducted "within one country or region" and then use regular mail (no tracking) to reship the chip to control the cost.

Regards,
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Old 12th May 2019, 04:01 AM   #150
nattawa is offline nattawa  Canada
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Quote:
Originally Posted by prasi View Post
To Nattawa,
The point JP is making is correct regarding safe mounting of SMD board. I tried it , vias still eat too much into copper even if i keep thin pads with 1.8mm dia. Here is how it looks.
Hi prasi,

In the amp where I intend to try the LT4320 rectifier, the PCB would be supported by the pin headers just like a regular SIL diode bridge supported by its own pins. There are no floating PCBs.

Thanks a lot for spending time trying on the added holes. But I guess I'd better design my own PCB to suit that particular need. I don't have to stick with DIP LT4320 and that would free up some space.
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