DIY Coin-sized SATA Power Module to Replace a Harddrive Docking Station

I find harddrive docking stations too bulky, slow, and unreliable. They are (1) inconvenient to carry when travelling light with a laptop, (2) offer relatively little throughput because the USB ones are limited to 480Mbps and the eSATA ones are often internally bottlenecked to 1.5Gbps due to the bridge chips they use (nevermind that none support SATA 6Gbps), and (3) are not reliable/act in strange ways when a drive is failing, which is sometimes the reason I put the drive in a docking station —to investigate it— and I wonder if it is the station or the drive that is failing.

Therefore I felt compelled to design and build a coin-sized SATA power module able to power a drive while the latter can be directly connected to a computer via a plain SATA or eSATA cable. I have used it for a couple of days and am very happy with it. Compared to a docking station, my solution is smaller, cheaper, faster, more reliable, and allows connecting any SATA peripherals (optical disc drives, SATA port multipliers):

Total cost and time involved were about 9 USD and one afternoon. The power module is compatible with any 12V wall adapter, as long as its current rating is sufficient for the drive —personally I use the 2A-rated adapter from the docking station it replaced :-) It steps down 12V to 5V, and supplies both voltages to the drive:



Design

Before I started this project, I knew that a SATA power cable theoretically supplies 3 voltages: 3.3V, 5V, and 12V, but that no drive on the market uses/needs 3.3V. I started by disassembling my Rosewill RX-DUS100 docking station to reverse-engineer the design and find how it was supplying 12V and 5V to the drive. 12V came directly from the output of the wall adapter whereas 5V came from the output of a chip labelled Techcode TD1509 which I quickly found out was, with 2 capacitors, a diode, and an inductor nearby, forming a circuit called a PWM buck DC/DC converter.

I must ashamedly admit I had never heard of buck converters before (hey, electronics is a hobby I rarely practice!) Now armed with the key piece of information I needed, I decided my plan will be to re-use the 12V wall adapter from the docking station, and to build a buck converter on a PCB as small as possible with a DC power jack as the input and a SATA power cable as the output.

I measured the current draw at 12V and 5V on a handful of harddrives and cross-checked with the HDD vendors' datasheets. Drives are never rated more than about 2.5A @ 12V and 0.7A @ 5V. In practice my measurements showed no more than 1.5A @ 12V and 0.6A @ 5V. Power consumption on the 5V rail is pretty much constant, whereas 12V spikes to ~1.5A during spin-up then falls back to ~0.5A. As to my docking station, its 12V wall adapter is rated 2A, and its Techcode TD1509 converter is rated 2A @ 5V (overspec'd because it powers a few other chips in addition to the drive.) With these number in mind, I decided to design my converter for minimum 1A @ 5V.

I searched around on Octopart, Digikey, and found many 5V buck converters. I reduced my search criteria to the high-efficiency, through-hole ones requiring few external components that were inexpensive. I settled on the Nat Semi LM2675, a 1A, DIP8 package, DC/DC converter to 5V. I implemented the reference circuit from the datasheet, and selected external components to match my design specifications (12V input, 1A @ 5V output.) Full bill of materials:

I found a layout that works well with this PCB, while minimizing the length of certain traces (eg. the Schottky diode needs to be as close to the LM2675 as possible):

Finally I put some heat-shrink tubing to finish the product:



Possible Improvement

The current design requires a 12V wall adapter because this 12V input is output directly to the drive. One could add another DC/DC conversion step (at the cost of increased board size) to regulate 12V, thereby making the SATA power module compatible with a wider range of input voltages, such as a laptop power adapter. One less adapter to travel with!

I would be very happy to see a commercial product like mine. I found only one on Newegg but it is still too bulky and clumsy to my taste (separate thick IEC power cord, brick adapter, 4-pin molex power cable, 4-pin molex to SATA power adapter).

mrb Saturday 12 March 2011 at 6:45 pm | | Default
Used tags: , ,

eigthteen comments

sr

Great article! Thanks!

Could you give more details on:

- “bridge chips” bottlenecks? (maybe another article on the docking station dissasembly?)
1.5Gbps is a bottleneck for SSDs, right? not spinning harddrives, yet?

- laptop having esata port (never saw one before, what’s on the picture?)

sr, - 13-03-’11 22:17
mrb

Bridge chips provide USB or SATA uplinks to a host (computer) and a SATA downlink to a device (drive). It is the most important chip in a docking station. It is very easy to identify when opening up a dock station, it is the biggest chip (BGA package). A common supplier of such chips is JMicron:

http://www.jmicron.com/Product_list.htm

For example my docking station uses the JMicron JMB20336. It is in theory capable of SATA 3Gbps according to the bridge chip datasheet, but I see it negotiate speeds of only 1.5Gbps with my laptop which supports 3G. On Linux, the SATA speed negotiated by a device is usually listed in the kernel messages (dmesg). JMicron has more detailled datasheets (but they are not available to the public), and I presume they state it supports 3G on the downlink, but not on the uplink. Of course the docking station is branded as “supporting 3Gbps”. Sigh :-/ Or perhaps the bridge chip downgrades to 1.5Gbps due to EMI issues, poor traces, who knows? That’s part of why I ditched my docking station, and others, after all.

So I built my module and, ta-da, all the drives and laptops I have now work at 3G with a passive SATA cable.

You are correct that 1.5Gbps is usually not a bottleneck with a single 7200 RPM HDD. However it is one when reading from the drive cache (which can mostly only be shown in synthetic benchmarks), as well as recent 15k RPM HDDs, SSDs, and also SATA port multipliers.

As to my laptop (Lenovo U160), yes it has an eSATA port. It was one of my requirements when I purchased it. The story of the amount of time I spent researching a laptop that met my needs is worthy of another blog post :-)

mrb, - 14-03-’11 01:03
sr

Merci encore pour les infos.

- I use this one http://www.ldlc.com/fiche/PB00080893.htm.. Will try to get the chip info. Needs also to test if esata hotplug has progressed.

- “from the drive cache”: ah yes, forgot this one.

- “amount of time I spent researching a laptop that met my needs is worthy of another blog post “ : yes, lots of laptops that are the same, but few features.
Other example: it seems impossible to find resolutions that were available few years ago (1440×900 12” or 1600×1200 14/15”). Even the X series does not seem to have an esata port!

sr, - 14-03-’11 01:50
Alex

A possible redesign you could go for a longer rather than wider approach. Try and fit as much of it as possible in the same height and width of the power connector. Making it look like just long plug.

Alex, - 14-03-’11 10:25
Roger

Parts from those supply houses get expensive when purchased one at a time and all the postage is added. Have you thought about putting together DIY kits and selling them for, say, 20% above cost? Many of us know how to solder or have a friend who does, we just don’t have the patience to round up the individual parts.

If you did this, a short Youtube video would be good advertising.

Roger, - 23-03-’11 14:05
mrb

Sorry I can’t sell kits.

However I hope you noticed I provided direct links to the exact Digikey or Sparkfun parts for this project, so there is no “hunting” necessary to find them.

mrb, - 24-03-’11 23:15
ACG

If there is anyone out there that has read this page top to bottom, I am interested in obtaining a few ‘kits’. Call it a first-timers’ worry-free order; perhaps I’ll successfully create one on the first try, though I would like to have a ‘testable’ adapter before creating very many. I see this as a business opportunity for someone, though have too much on my plate right now to even think of creating a quantity order for adaptation/sale.

ACG, - 16-04-’11 20:35
ACG

address.unknown@myfairpoint.net is a legitimate eddress.

ACG, - 16-04-’11 20:36
Portable Hard Drive Deals

Looks difficult, will do it anyway!

Portable Hard Drive Deals, (URL) - 22-09-’11 23:20
Dude

I need something like this, many thanks for the links to the parts mrb. Does your sata to esata cable have the required extra shielding of an external interconnect? Perhaps you are not too concerned if it is just for testing purposes.

From the External Serial ATA White Paper.

Additional steps were taken to modify the cable by adding an extra layer of shielding surrounding both of the differential signal pairs in the cable. In a standard internal cable, each pair is shielded individually. This shielding remains in the external cable, but an additional over wrap is also provided.

Dude, - 16-10-’11 16:56
mrb

The SATA to eSATA cable in the picture does not seem to have this extra shielding. But I have a few other cables that have it.

The SATA protocol has built-in error correction anyway, but I would say if you have the choice, be conservative and go with an extra-shielded cable to reduce the theoretical error rate.

mrb, - 16-10-’11 18:43
Dude

Thanks for the info. Are you able to put up a picture of the reverse side of the hex board after the parts are mounted. That way I can follow the physical traces. I am pretty newb to reading electrical schematics (even simple ones).

Dude, - 17-10-’11 03:08
mrb

I am sorry. I already put heat-shrink tubing. I would have to cut it open…

mrb, - 17-10-’11 20:51
Lucas Anthony@laptop overheating problem

please be more specific. i want to apply this on my laptop. this idea of your is interesting.

Lucas Anthony@laptop overheating problem, (URL) - 25-10-’11 19:43
Ryan Gibson

Hey,

Great build you’ve put together here. Do you have an email I can grab you on? I have a few questions i’d love to send your way.

Thanks

Ryan

Ryan Gibson, (URL) - 02-02-’12 02:06
mrb

My email address is listed on my personal page: http://www.zorinaq.com

mrb, - 02-02-’12 19:25
Joerg

Good stuff, thank you! I would like to build a NAS using the marsboard. I am thinking of building a similar rig to power a 3.5” drive. It would be great if I could also throw in a USB supply to also power the marsboard itself from the same plug.
Would it be possible to run the marsboard in parallel to the SATA 5V line, or would that need to be decoupled – and how?

Joerg, - 27-11-’13 04:41
mrb

Yes the 5V output of my module can be fed into both SATA and USB in parallel.

mrb, - 29-11-’13 00:56
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