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Offline mamu

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PTH08T221W - 16A 88W w/ UVLO...
« on: June 02, 2014, 11:14:03 PM »
Features:
16A, 88W
Input: 4.5 - 14V
Output: 0.69 - 5.5V
Adjustable UVLO

2 versions - PTH08T220W and PTH08T221W.  I chose to work with PTH08T221W (ceramic cap version).

Datasheet here:  PTH08T221W

Tiny profile for a 16A module (23mm x 20mm x 9mm)...


Size comparison with the OKR-T10, OKL2-T20, and Raptor 20A...


So I go to solder wire to the pins to get it breadboarded and start by tinning the pins on the board.  The instant I touched the pin with the soldering iron - the friggin pin loosened and tilted sideways.  All of them, except pin 3, immediately loosened and tilted when I touched the soldering iron to it.  gawd lol.

I spent the next half hour or so using flux and a desoldering braid to remove all solder in all the pin holes.  It actually turned out to be an advantage that the pins came off because now I have a through hole module for wiring and with even a lower height.

Height between the through hole version compared with as it comes from the manufacturer...


All wired up but holy moly - see how close some of those onboard components are to the pins?  This would not be recommended for someone new to soldering...


I'm not using Track, Sync, and TurboTrans.  As per datasheet, connected Track to Vin, Sync to ground, and TurboTrans open.  All other pins of this converter are in use and wired as shown in the above pic.

I connected Track on the front of the board...


and Sync to the back of the board... I lined the back of the board with several layers of Kapton tape first...


Added 3x 100uF (parallel) input and output ceramic caps to the back of the board... I'll either secure these caps with epoxy or change where I placed them before putting the converter in a mod...


Now breadboarded...


I'm using a 1K POT plus 4.7 ohm trim resistor for an output voltage range of 3.5 - 5.6V.

An NC fire switch is required to turn on/off inhibit - the inhibit of this converter requires a switch that must be closed in order to turn OFF output and open in order to turn ON output.  That's the short layman's version - read the datasheet for the reason behind this.

I removed the NC switch and took the pic above with an NO tact switch - didn't have to press the button.  :laughing:

I'm not keen on NC switches plus there is a very limited supply and type.  If I can't find a work around, what I'll probably do is use a FET to handle current and wire in a non-rated NO switch on Vin.  The datasheet indicates that I should still have UVLO with this configuration with the appropriate resistor placed between inhibit and ground.

I've emailed TI tech support with some questions and am waiting to hear back.

Next step is to test the UVLO feature.  I bought resistors to test at different voltage cutoffs - 6.0V, 6.2V, 6.4V and 6.5V.
« Last Edit: June 03, 2014, 08:15:29 AM by mamu »

Offline Visus

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #1 on: June 03, 2014, 01:03:54 AM »
 freaked_out:
Already

woot

lol   

cute baby jumper there on gnd stripping wiz, no oops
the pot is kewl lookinz prolly takes kewl topper

no reviews yet on that module your in a league by yourself with it, it looks like
Ti engineers are like, 'do we have a pth08t221w
wont be far off, more off the shelf

18ga solid?

Offline mamu

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #2 on: June 03, 2014, 03:57:29 AM »
Fixed that - happy now?  :laughing:

I use 20ga solid wire for all pins with my breadboarded converters.  If a converter is new to me,  I always wire up that first one so it is breadboard friendly.  And since I only have 20ga solid wire on hand, all pins get the same. 

One converter of each of the converters I work with - DNA, OKR, Raptor, OKL2, now this one, I wire up breadboard friendly and set them aside for the just in case.  It's comes in handy if I need to re-visit the wiring configuration or test something and have to put it back on the breadboard.

Offline mamu

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #3 on: June 03, 2014, 08:53:02 AM »
Update: a work around for not having to use an NC switch and instead use an NO switch has been tested and is working aok.  Thanks so much to MJarvis for his help in locating the schematic that shows this - and of all things with an Evercool board.

I should call this converter Evercool on steroids. :laughing:  Both datasheets have some sections almost exactly the same word for word.

Inverting the logic of the inhibit pin on TI PTR08100W

Now I have only 2 concerns with this, not with the N-FET, but with the 10K resistor.  One is will the 10K interfere with the internal pull-up resistor (datasheet says an external pull-up resistor should never be used with the inhibit pin) and will this interfere with the UVLO monitoring at inhibit.  I'll be testing and watching. 

I didn't have the part listed in the schematic so instead used the N-FET I bought for this converter in case I needed it.  Here it is breadboarded.  Working like a champ - no firing when not pressing the NO tact switch and fires when pressing the switch.

« Last Edit: June 03, 2014, 09:02:11 AM by mamu »

Offline warlordxxx

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #4 on: June 03, 2014, 10:29:27 AM »
You're welcome Mamu :D If the UVLO still works ok with it then it's golden and like you said an evercool on steroids lol

Offline Visus

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #5 on: June 03, 2014, 01:51:35 PM »
Awesome


Lol

Working breadboard models of every one, must look cool as heck on the shelf.  Instant recall when needed.. 

Hope tha uvlo works, it would seem you definitely changed the dial of it with the parallel 10k + internal  pull up, but if no change from interrupt from pull up that would be huge and uber easy.

 8)

Offline mamu

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #6 on: June 05, 2014, 05:56:52 AM »
The converter is working aok with the N.O. switch how I have it wired with the NFET, but I am having a problem with UVLO.

The actual cutoff voltage is not matching the calculated voltage - at all. Example: I used a 28.7K UVLO resistor. Calculated cutoff voltage is 6.5v, but the actual cutoff voltage is 4.4v. I used a 15K UVLO resistor. Calculated cutoff voltage is 8.4v, actual cutoff voltage is 5.8v.  There is a 0.5v hysteresis to account for some of this, but more than 2v like this is really off.

The results are the same when using a (FET + 10K pull-up resistor + N.O. switch) and (N.C. switch with no pull-up or FET).

After tinkering with various value resistors and seeing what actual cutoff voltage is vs calculated cutoff voltage, I think we're lucky that we have a narrow cutoff voltage range and that range seems to be in a linear portion because the fudge factor of calculated vs actual is the same for our cutoff voltage range.  Outside of that range, the fudge factor changes.

So now I need to buy various UVLO 1% resistors in the range of what I want actual cutoff voltage to be.  I was testing with the resistors I have on hand and some are 1% and some are 5% and some I had to series to get the value I was testing. 

Off to mouser to buy some resistors, then to bed.  Maybe I can get some sleep now. :laughing:

Offline mamu

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #7 on: June 07, 2014, 06:48:26 AM »
Three 221 versions are available - I ordered one of each from TI.  Gotta love getting free samples.  :laughing:




Offline Visus

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #8 on: June 07, 2014, 04:55:11 PM »
Mamu I know you love your accuracy in your mods, take a peek a dave's last lesson on ceramic caps.   
From v in to dialed, things can get a bit changed there.  Good vid explaining what happens.  Seems electrolytic would be better option for us; ceramics--it halves the cap rating when v drops, when v bias demand goes up(battery use)  they work best steady regulated rail.   :Thinking:


https://www.youtube.com/watch?v=2MQyQUkwmMk

Offline CraigHB

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #9 on: June 07, 2014, 05:30:55 PM »
I've mentioned that before on the forum here, MLCC caps (aka ceramic) have something called a DC bias effect which can be a real PITA. 

Not all ceramics have a DC bias effect, the COG/NPO dielectric types do not have any at all, though they are not available with higher capacitance values.  High value MLCC caps typically use an X7R or X5R dielectric that in some cases can have pretty extreme DC bias effects.  In other cases, not as much.

Temperature stability can also an issue with MLCC caps, but if you stick with X7R or X5R dialectrics (there's no reason not to), it's generally not a concern or generally a big ding against ceramic caps.

That's not to say that other capacitor types are better.  Electrolytics have several disadvantages in that ESR is much higher, they occupy a lot more space, they are polarized, and have less tolerance for voltage ripple.  That's a lot of downsides compared to essentially one downside for an MLCC cap.

You can find other types with some of the advantages of an MLCC cap.  For example, you can get organic aluminum polymer caps that have much lower ESR and higher ripple tolerance.  You can get tantalum polymer caps that also have much lower ESR, but neither are as low in ESR as an MLCC cap nor can they hanlde as much ripple.  Those other types are still polarized as well.

ESR is a biggie in that it has a marked effect on how well a capacitor does it's job.  Higher ESR makes a capacitor less effective requiring more capacitance and more size to make up for it.  It can also introduce considerable power loss in power filtering applications.

Ripple tolerance is important because a capacitor in a power filtering application has to handle a lot of it.  If a capacitor does not have the required ripple tolerance, it will overheat and fail.

When using MLCC caps you need to be aware of their DC bias characteristic.  It varies depending on a number of factors so you have to consult the part's characterization sheet.  Other than that, they significantly outperform other capacitor types.  If it not for their DC bias, they're as close as you can get to an ideal capacitor.

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #10 on: June 07, 2014, 07:08:34 PM »
Great explain there craig, so when a data sheet suggest the caps it has taken this into account throughout its range.  Thats awesome  I can understand why they do not like pots used on some modules now per on board caps and bias..

Offline CraigHB

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #11 on: June 08, 2014, 04:19:24 AM »
Here's a couple examples for you.

Take a look at this characterization sheet; http://product.tdk.com/capacitor/mlcc/en/documents/C3216X5R1A107M160AC.pdf

Notice the DC Bias chart in the top right.  You can see that at 8V, the capacitor loses 85% of its capacitance.  Though it's a 100uF capacitor, it only has 15uF capacitance with an applied DC voltage of 8V.  That would not be a good capacitor to filter input from series cells.

Now take a look at this characterization sheet;  http://product.tdk.com/capacitor/mlcc/en/documents/C3225X5R1C226K250AA.pdf

At 8V this one retains 85% of it's capacitance.  Though it's only a 22uF capacitor, with an 8V DC bias it actually has more capacitance than the 100uF capacitor.

Also compare the temperature characteristic and the ripple temperature rise.  You can see the 22uF capacitor again performs much better than the 100uF capacitor.

One thing to notice for both these caps is the very low ESR seen in the ESR vs Frequency chart.  Under 1MHz these capacitors have only 2 mOhms.  The lowest you can find the aluminum and tantalum polymer types is about 5 mOhms and those are the most expensive.  An aluminum electrolytic capacitor ranges between 50 and 200 mOhms.  The standard tantalums are even higher, as much as 3 Ohms. 

The other capacitor types do have their niches.  MLCC caps are not widely available with high values and high voltage tolerance.  For those requirements, you need to use something other than an MLCC cap.

Offline Visus

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #12 on: June 08, 2014, 04:11:04 PM »
Holy cow you just brought us up to spec on choosing the better caps.

When module data request @ 100uf to its efficiency rating, I am definitely not getting close to its 93% efficiency with the caps I am running now..

Priceless Info

Cant make heads or tails out of the tan caps data sheet I am using
dc bias drop except it is 10% rated and freakin almost 1ohm ESR  lol whoa
no cool voltage plot charts  except for temp and esr  they do give the math figure
but whoa math gimme a beer and pretty charts lol

https://www.avx.com/docs/Catalogs/TAPTEPTECHSUMMARY.pdf

Offline CraigHB

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #13 on: June 08, 2014, 05:12:40 PM »
That's pretty typical for a standard tantalum cap.  Though, you're right, those charts are not very good in that data sheet, hard to read.  Big difference from the TDK charts.

Keep in mind ESR becomes more critical with low impedance stuff, like when using them to filter a power supply.  Tantalum caps have good temperature stability and no appreciable DC bias so for high impedance stuff, like filtering digital signals, that higher ESR is not necessarily a problem.  They're much smaller than an electrolytic cap in higher capacitance values so they have that advantage. 

Tantalums are kind of falling by the wayside anymore.  They have a big size advantage over electrolytics, but the high value MLCC caps have taken over their niche for the most part.  Keep in mind it's only in the last decade that high value MLCC caps have become inexpensive.  They used to be cost prohibitive.

Pretty much nothing beats the small size of a ceramic.  For high density stuff, the only time they're not used is when they can not meet requirements in some area.  For example, if you need high voltage tolerance with high capacitance or if you need higher temperature stability. 

There's also the cost consideration.  MLCC caps get a lot more expensive when you get into the high values.  For high capacitance, you can't beat the low cost of a standard aluminum electrolytic.  That's why you still see them used heavily when you look at the PCB in consumer electronics devices.  Though the aluminum polymer caps are kind of taking over there.  You see them used a lot now.  They perform better than the standard aluminum electrolytics and there's not a big cost disparity there.

Offline mamu

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #14 on: June 08, 2014, 08:39:17 PM »
Keeping in mind space constraints and total uF required, I chose 100uF/16v/X5R/1210 ceramic caps - 3x on input and 3x on output.  The cap datasheet is worthless for specs.  It would be nice if TI would put more caps onboard so we wouldn't have to get into the high capacitance range for external caps.  Having to buy 6x 100uF caps cost almost as much as the converter.

The caps I had chosen (what was actually available) weren't listed in the TI datasheet, so I asked TI tech support and he said they were acceptable.

When I tested UVLO across various input voltage cutoffs, I also kept an eye on output.  Haven't noticed any issues with voltage regulation at lower input voltage until it gets to the cutoff voltage, then I get a bit of oscillation on output, then the converter quits firing.

Getting ready to put this converter in a mod.  I chose a 6.4v low voltage cutoff (resistor sets unloaded cutoff).  All the resistors, caps, and N-FET are tied to the board.  Makes a nice small 1" x 1" package...



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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #15 on: June 08, 2014, 09:50:18 PM »
Badarse Mamu

My cheaper build would have 1 on in, 1 on out hopefully do gewd enough for our use...  Especially after I saw the ceramic prices lol
 :laughing2:

http://www.digikey.com/product-detail/en/16SEPC470M/P16299-ND/4204136




Offline mamu

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #16 on: June 08, 2014, 10:13:11 PM »
You only need min 300uF on in and out, Visus.

If you're going to go with the aluminum polymer caps, this might be a better choice and with a bit of a lower ESR: http://www.digikey.com/product-detail/en/RR71C331MDN1/493-3718-ND/2207254

Still really big though.

Offline Visus

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #17 on: June 09, 2014, 12:31:08 AM »
They are huge lol omg I ferget about that part

10mm dia X 12 mm  godzilla of caps  fainting:

ok you have convinced me to go with ceramics since your running stable but I read

Quote
When using the PTH08T220W, observe the minimum ESR of the entire output capacitor bank. The minimum
ESR limit of the output capacitor bank is 7m?.
caps you added work great on 220w

I have also read

Quote from: page 14
When using the PTH08T221W without the TurboTrans feature, the maximum amount of capacitance is 3000µF
of ceramic type. Large amounts of capacitance may reduce system stability.

The caps I choose for 220w are 4700 total µFxm? used only with turbotrans

The ones you added are 2310µFxm? total   phew, learning is awesome  :thumbsup:

Ceramics much lower esr X capacitance  = greater stability = awesome  :thumbsup:
The ceramic module 221w may be the one to go with, its not approaching tolerances..

No reason to penny pinch around with ti and kindness to my style of builds
My nickname is fox after redfox from sanford and son lol
If I could measure the caps on my old puters then aha
or get the schematics and toaster oven later, oh yeah

Thanks

Offline CraigHB

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #18 on: June 09, 2014, 12:56:53 AM »
The problem with MLCCs is that when you get into a high capacitance value like 100uF, you have to use a bigger part to get the DC Bias within an accepatable range.  That's how it works with DC Bias and MLCCs, the bigger the part, the less they have.  It really comes down to that for any MLCC though there is some variance from one part number to the next. 

22uF is about the highest you can go with a 1210 size part (3225 metric).  To go as high as 100uF with an MLCC, you need to use a really large part like this one.  Even then, DC Bias is about 50% at the rated voltage.  To get those high capacitance values, you need to go with a different type of capacitor.  When you need high capacitance, there's just no way to get around the size requirements.

OS-CON is the Panasonic brand aluminum polymers.  In general the aluminum polymers are really good caps.  They have low ESR, high temperature stability, good ripple tolerance, and good service life.  The main down side is they're kind of big and of course they're polarized.  Looking at the Mouser listings, there's this one.  It's relatively inexpensive and not terribly large at 8 x 8mm.

You can also look at the tantalum polymers for low ESR and small size.  They're a bit pricey, but they'll be a lot smaller than the aluminum polymers.  Here's a listing at Mouser for 10V 220uF and 330uF.  The 330uF ones are really expensive so if you can get by on the 220uF ones they're cheaper.  They're only 10V and it's it's better to use a higher rating, but going to 16V with tantalum polymers is cost prohibitive.

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #19 on: June 09, 2014, 04:06:39 AM »
I watched the video knew there was something in to it but Mamu has a stable output so was kewl with it there lol..  Now you had me re-read cause your right it will be @ 50 capacitance which is well below optimum specs.  I read and read again and what d  ya know they give ya the optimum set-up without using the turbo trans..

Quote from: page 13
The PTH08T221W requires a minimum input capacitance of 300µF of ceramic type.
The PTH08T220W requires a combination of one 22µF X5R/X7R ceramic and 330µF electrolytic type.

Thinking getting close to maximum tolerance was a bad thing I read right over this..

Quote from: page 14
If the TurboTrans feature is not used, minimum ESR and maximum capacitor limits must be followed. System
stability may be effected and increased output capacitance may be required without TurboTrans.

I wonder if Mamu's setup at uvlo and the start of oscillation; would changing the caps work it out.

They recommend adding up to 330uf with 10uf I know thats whoa but known dc biasing also softening the transients which may not become apparent initially since some build across time.. 

.
Quote from: page 15
Generally, with load steps greater than 100A/µs, adding
multiple 10µF ceramic capacitors plus 10×1µF, and numerous high frequency ceramics (?0.1µF) is all that is
required to soften the transient higher frequency edges.

Worst case scenario:
Using the turbo trans is looking rather lovely since it lowers need for caps and makes sure those transients don't show up knocking later if/as switch and fets cause static havoc.

lol its me bad time now,  I wanna dial in the 08100 better if can be - see what it does  -tomorrow.  :thumbsup:

Offline mamu

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #20 on: June 09, 2014, 07:54:07 PM »
I emailed TI tech support about the loss of capacitance due to DC bias voltage, he said "Input Large Ceramic  capacitors have DC bias voltage drift and temperature up to worst case 30% of each capacitor.  This lower total input capacitance is considered when determining minimum operating input ceramic capacitance."

Visus, all my buck converter mods oscillate on off output voltage under load when the input voltage is near or at cutoff voltage.  There's not enough current to sustain the voltage at min input cutoff.  With my Raptor mod, when input gets at that 6v cutoff under load, output oscillates on off for a few draws and then the converter quits firing.  So this converter is not doing anything unexpected.

I'm not getting an output voltage deviation (except of course at min input voltage cutoff), so TurboTrans and those additional caps aren't needed.  That being said, I'm not testing under the full 16A so results there might be different.


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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #21 on: June 09, 2014, 08:13:47 PM »
Thnaks Mamu was wondering because normal shutoff is much lower than 6.4v.  Thats just how it goes with regulators then, because my ego twist did it and 4050's 08100 etc do it.  It would be so cool just boom no more, off..   The provari supposedly does just that, no oscillates it just goes boom,, off'-- per busardo chats on yt,  not tested myself and he minutely judges other mods by that.. It is cool..  :yes"

I did find on the 08100 data sheet a request for optimum opps: 100uf cap and a 22uf ceramic to stop transients)  I get a load sag of .1-.2 depending on coil build, higher ohm .2 lower subs .1 .  Like you said Mamu,  it would be awesome to know which resistor controlled the uvlo and the math to change it-- maybe the same as the 221w..  Not like I could desolder or solder that lil mofo, but maybe  lol...  Thats a great feature..


How is it performing battery time against the new okl runtime champ?
 :popcorn:


Offline mamu

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #22 on: June 09, 2014, 08:37:13 PM »
A supervisory IC with hysteresis would do that for us, Visus. 

The TI tech support guy linked me to this when I asked him for a chip that would shut-off firing for the voltage shutoff range we work with: http://www.ti.com/product/tl7712a/samplebuy?keyMatch=tl7712acdg4&tisearch=Search-EN

I also found another one that I have coming in.  I want to work with it for the OKL2-T20 which has nothing that will shut off firing at low voltage.  I found sometimes I'm not paying attention to the low volt indicator I installed.

That shut off of 6.4v is unloaded, not loaded.  I could have chosen a resistor that would give 6.2v unloaded shutoff because my Sony batts are dropping 0.2 under load at min cutoff voltage, sometimes 0.3v under load though.  So I gave it a bit of a cushion by choosing 6.4v.

I chose to work with this converter because of the internal UVLO and the small footprint for a 16A module.  But after working with it, the biggest disadvantage is having to add 6x 100uF caps and the cost of those caps as well as wiring in those caps.  It makes it fairly expensive considering we have lower cost alternatives to high amp converters.  But I do like the small size of it and that it has the internal UVLO.  We'd be all set if TI would get on board and add more capacitance to the board with their converters.

Offline Jasen

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #23 on: June 09, 2014, 08:38:01 PM »
OK I need to go drink a couple beer's now, I think I broke my Hippocampus reading the last 10-12 posts.

Keep up the brain storming :thumbsup:

Offline CraigHB

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #24 on: June 11, 2014, 12:02:47 AM »
I emailed TI tech support about the loss of capacitance due to DC bias voltage, he said "Input Large Ceramic  capacitors have DC bias voltage drift and temperature up to worst case 30% of each capacitor.  This lower total input capacitance is considered when determining minimum operating input ceramic capacitance."

I think he was talking about ones bigger than 1210, more like 2220 like the one I posted the sheet on before.  If you're using 100uF 1210 caps, you're not getting better than 50uF per capacitor at 8V, possibly less.  Smaller case size = more DC bias.  That's what the charts always show.  For example this 1210 100uF part; 

http://www.yuden.co.jp/eu/product/category/capacitor/putpdf/LMK325ABJ107MM-T_SS.pdf

You really have to look at the characterization sheet for any high value MLCC cap.  The one I listed above is the absolute best 100uF 1210 cap I've found.  I have that capacitor on hand from a non-ecig project.  Others I've looked at with that value and size have a less favorable DC bias characteristic.  I'll only use that capacitor in applications with a DC bias under 3V otherwise it loses too much capacitance.

In any case, it's not a big deal.  That regulator is designed to run within spec with no caps at all, yeah?  So, adding more or less capacitance should not be an issue.  Even if the caps are required, they said they've compensated for DC Bias in the design, but you're running with somewhat more than 30% loss, on input at least.  Output voltage is lower so there's less of a loss there.

Offline ride_bmx_mhell

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #25 on: June 11, 2014, 01:14:26 AM »
hi mamu, what trimmer resistor value should i use if i want a voltage output of 2.85v - 5.50v with this chip? :think:

Offline mamu

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #26 on: June 11, 2014, 02:17:19 PM »
I'm only going to make a few mods with this converter, Craig.  With the extra cost of the caps, the N-FET, and the hassle of extra wiring it's not really a feasible converter for us.  The UVLO is not consistent, so I have to find a work around for that.  The TI tech guy told me:

"There is no guarantee that the resistor selected will always shut it down at 6.4V.

When the input voltage sags to constant lower voltages, not decaying voltage to 0V, the input current sources more current .

At 6.4Vconstant voltage , with your load, battery source  increased  current can force the  output voltage  to oscillate, on-off, until the battery can no longer sustain  the voltage.

The TPS3838 series SVS  a selectable delay  of from 20msec to 100s of msec which will prevent this oscillation."

bleh... :laughing:

hi mamu, what trimmer resistor value should i use if i want a voltage output of 2.85v - 5.50v with this chip? :think:

Look in the datasheet for the resistor value that gives you the low min voltage you want.  Choose a POT close to that resistor value given for the low min voltage you want.  The 5.5 output voltage is set by the 4.7 ohm resistor and that's such a low value that it doesn't need to be added to the value of the POT.

I'm using a 1K POT plus the 4.7 ohm resistor which gives me a range of 3.5v - 5.5v.  Higher POT ohms will give lower output voltage.  A 1.5K POT plus the 4.7 ohm resistor gives a range of 3.0v - 5.5v.  You can also use the equation provided to calculate what POT ohms you need for a min of output of 2.85v.

Offline CraigHB

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #27 on: June 11, 2014, 08:23:06 PM »
P
I'm only going to make a few mods with this converter, Craig.  With the extra cost of the caps, the N-FET, and the hassle of extra wiring it's not really a feasible converter for us.

Probably good enough for government as they say.  Interestingly the TI TPS43061 converter controller I'm working with right now has the exact same function on the enable pin as it's called in that part's data sheet.  Though, I don't need it since the MCU handles under-voltage conditions.  I just tie that pin to supply voltage.

Offline joubjonn

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TI PTH08T221
« Reply #28 on: August 20, 2014, 10:41:14 AM »
Hello! really appreciate the forum, wouldn't have been able to build the two mods i have now without it!

So i bought a TI PTH08T221WAD Chip, 16 Amp 88 Watt, nice specs. However i'm getting a weird reading off it. I believe Mamu has mentioned this chip on the forum here.

I wired it up with SMD Neo Tantalum caps, 300 uF low ESR. NEF jN8 type on the input and output, directly at the wires coming off the chip. The -Sense was soldered on the board directly to the GND, + sense was soldered to the output on the board. i'm using a 5k ohm pot at Vo adjust pin to give me around 1.7-5.5V output. Track pin is connected to Vi (not used), Turbo Trans pin left open (unused), SmartSync connected to GND pin (unused). Used a UVLO resistor at 23k ohm for 7V threshold.

 it works great when i fire it up, i had my Fluke 87 hooked up to it and i noticed when i let go of the fire button (the fire button is directly connected to the Vi instead of using the Inhibit/UVLO pin, the voltage drops off slow, takes about 3-4 seconds to get back to 0 volts. was wondering if anyone had an opinion on that.

Also, what would be the easiest way to use the Inhibit pin? so i could use a lower rated switch for a firing button. Appreciate the help!!

Because of this forum i have built a LSS/T10 mod (basically the same as the OKR/T10) with a 2S 1300mAh Lipo (have to use the special 2S/3S charger every night but thats ok  and a OKL/T20 mod with x2 18650, did not use capictors on either build, they work great, vape on them both daily, all day. no issues at all.


Online Breaktru

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #29 on: August 20, 2014, 02:38:22 PM »
I moved your post to the appropriate topic/thread.

I don't believe that you can use Pin 11 as an Inhibit if you are also using it as a UVLO. I think it's either/or.
See page 24 of the datasheet. It mentions using a discrete transistor BSS 138.

As far as the output slowly dropping: Did you have a load on the output when you measured output voltage?

Offline joubjonn

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #30 on: August 20, 2014, 09:50:23 PM »
no the switched I used was either fully on or off. I think maybe it was the fluke reading a slower response and picking up the drop off voltage fast. if that makes sense. appreciate the response.  I'm thinking of setting up a nice power supply to test the UNder volt protection. where I work, we have lots of electronic equipment I can use. I would like to know if it's reliable.

I also picked up the lower input voltage of this chip. I believe it is 2.2-5.5V input with 16amp 3.6V max output. a smaller box with 1x18650 or 1S lipo.

wish I would have found this post a long time ago! appreciate all the background info Mamu!

Offline shandy27

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #31 on: August 21, 2014, 04:48:30 AM »
With all this talk about uvlo, I was thinking. With the inverted logic for the switch would it not be possible to wire a zener diode before the 10k resistor in that schematic.

Offline glenn1210

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Re: PTH08T221W - 16A 88W w/ UVLO...
« Reply #32 on: February 20, 2015, 07:58:08 AM »
hey friend, its me glenn from philippines. just wanna ask you a question, im building a vv mod with a pth08t220WAH chip on it. and im having a hard time to fix the voltage control, im using a 2.2k vishay pot without a resistor. and adjusting the pot to lowest will not display any on my volt meter. did i do my wiring wrong ? or do i really need to put a resistor on +pin of my pot. thankyou bro, hope you get what im trying to point out. if u need a picture of my wiring just let me know. thanks

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