Welcome to our peer-to-peer forums, where owners help owners. Need help now? Visit eSupport here.

English Community

ThinkPad TabletsThinkPad Tablets
All Forum Topics
Options

1808 Posts

08-17-2011

USA

5548 Signins

38544 Page Views

  • Posts: 1808
  • Registered: ‎08-17-2011
  • Location: USA
  • Views: 38544
  • Message 161 of 411

Re: TPT2 has USB port power issue

2013-01-26, 6:56 AM
LOL Nah, more like "Les Money Hungry". ;)
===================
Don't get mad, get root.
3679CTO
Reply
Options

23 Posts

01-16-2013

Australia

28 Signins

178 Page Views

  • Posts: 23
  • Registered: ‎01-16-2013
  • Location: Australia
  • Views: 178
  • Message 162 of 411

Re: TPT2 has USB port power issue

2013-01-26, 17:05 PM

FYI:

 

Livescribe Pulse pen uses 250mA

 

Stingray USB Oscilloscope uses 160mA

 

Both of these may well be supported by the less than full power USB port of he TPT2.

 

Still interested in the TPT2 as it is lighter and smaller all round than the Dell Latitude 10.

Reply
Options

23 Posts

01-16-2013

Australia

28 Signins

178 Page Views

  • Posts: 23
  • Registered: ‎01-16-2013
  • Location: Australia
  • Views: 178
  • Message 163 of 411

Re: TPT2 has USB port power issue

2013-01-26, 17:20 PM

Now not available online in Australia until April 2013.

 

Probably means they are going to rejig a few of the things that have been problems, like the USB.

Reply
Options

165 Posts

12-10-2008

United States of America

2299 Signins

13298 Page Views

  • Posts: 165
  • Registered: ‎12-10-2008
  • Location: United States of America
  • Views: 13298
  • Message 164 of 411

Re: TPT2 has USB port power issue

2013-01-26, 20:28 PM

If I bought two TPT2s, could they power one drive via Y-cable?:smileytongue:

Reply
Options

226 Posts

10-08-2011

Florida

1049 Signins

4987 Page Views

  • Posts: 226
  • Registered: ‎10-08-2011
  • Location: Florida
  • Views: 4987
  • Message 165 of 411

Re: TPT2 has USB port power issue

2013-01-27, 19:21 PM

The TPT2 user guide makes reference only to keyboards, mice, and thumb drives.  From page 23:

 

Using the USB connector
Use the USB connector to connect a compatible USB device, such as a USB mouse, USB keyboard, or USB
memory key. To locate the USB connector on your tablet, see “Tablet layout” on page 1 .
Notes:
• The USB connector is compatible with the USB 2.0 standard.
• The USB connector can provide a maximum of 2.5 W power output.

 

http://download.lenovo.com/ibmdl/pub/pc/pccbbs/mobiles_pdf/tablet2_ug_en.pdf

 

 

 

Is 2.5W standard, meaning this problem is unintended, or is it substandard meaning the problem is by design?

JC

Reply
Options

135 Posts

01-19-2013

Austria

132 Signins

1387 Page Views

  • Posts: 135
  • Registered: ‎01-19-2013
  • Location: Austria
  • Views: 1387
  • Message 166 of 411

Re: TPT2 has USB port power issue

2013-01-28, 8:55 AM

A port is USB 2.0 compliant when it fulfills the USB 2.0 specs and they state - as already layed out in a former post on this thread - that it has to provide at least 100mA immedately when the device gets plugged in. During the enumeration process the device can apply for up to five times that current meaning 500mA.

 

Since the specs state that voltage can range between 4.75V and 5.25V.

 

Given the fact that power [P in Watts] is the product of voltage [U in Volts] and current [I in Ampere] and the statement of the manual that the connector should provide up to 2.5W, you'd come to several combinations:

  1. Given supply voltage 4.75V: 4.75V * 0.500A = 2,375W -> within manual and specs
  2. Given supply voltage 4.75V: 2.5W / 4.75V = 0.526A -> within manual and exceeding minimal specs 
  3. Given supply voltage 5.00V: 5.00V * 0.500A = 2.5W -> within manual and specs
  4. Given supply voltage 5.25V: 5.25V * 0.500A = 2,625W -> within specs, but not promissed by manual
  5. Given supply voltage 5.25V: 2.5W / 5,25V = 0.476A -> within manual promisses,  but not complying to specs

Conclusion:

Given the specs are fulfilled and the manual is correct the TPT2 USB port HAS TO HAVE a voltage range between 4,75V and 5,00V (above 5.00V is not allowed, since the 2.5W limit the current to currents below the USB 2.0 specs demands) and HAS TO BE ABLE to drive a current of 0.5A (500mA).

 

OR

 

The USB 2.0 specs are not fulfilled and the port is merely USB 2.0 "compatible" but not complient. In this case Lenovos advertisements and videos (e. g. one reference on this thread) are somehow missleading, exploiting the gullibility of customers, which is not to suitable for a company that respects its customers.

 

 

Reply
Options

391 Posts

08-25-2011

Iran, Tehran

3812 Signins

8808 Page Views

  • Posts: 391
  • Registered: ‎08-25-2011
  • Location: Iran, Tehran
  • Views: 8808
  • Message 167 of 411

Re: TPT2 has USB port power issue

2013-01-28, 9:13 AM
They must hire you ScruffR, at least you know how to do maths.

I think it is now the time that Mark comes and asks us again about which HDDs/Devices we tried, as if there's no one in Lenovo to test TPT2.

The funny thing is that TPT2 is their flagship, kinda.
----------------------------------------------------------------
ThinkPad Tablet 2 - 367927U
ThinkPad Tablet - 183822U
Reply
Options

23 Posts

01-16-2013

Australia

28 Signins

178 Page Views

  • Posts: 23
  • Registered: ‎01-16-2013
  • Location: Australia
  • Views: 178
  • Message 168 of 411

Re: TPT2 has USB port power issue

2013-01-28, 10:15 AM

Basically if all the TPT2s cannot supply the 2.5W (approx. within tolerances of voltage), as stated on p23 of the manual, then it is design problem that will not be easily fixed, which is probably why it's supply from Lenovo has been delayed by three months.

 

Of course, some sellers may still have stocks they want to move.

 

Let's see what the capabilities are by the time it is available again. Perhaps a beefed up USB, LTE and whatever else the market counts as the minimum that needs to be laid on the table.

Reply
Options

23 Posts

01-16-2013

Australia

28 Signins

178 Page Views

  • Posts: 23
  • Registered: ‎01-16-2013
  • Location: Australia
  • Views: 178
  • Message 169 of 411

Re: TPT2 has USB port power issue

2013-01-28, 10:27 AM
Convention has it that the power is always quoted at the nominal voltage (5.00) and current (500mA).

If the voltage is at the low end of the tolerable limit, then the power will be down proportionally, but that is still within spec.

Running any motorised peripheral close to the maximum spec is always risky because even a little bit extra mechanical resistance to the motor may put it over what the port will be able to supply as the drive circuit tries to pull more power to overcome the resistance.

One would really want a nominal maximum of around 450mA drawn by a motorised peripheral to be sure that power spikes can be handled.
Reply
Options

135 Posts

01-19-2013

Austria

132 Signins

1387 Page Views

  • Posts: 135
  • Registered: ‎01-19-2013
  • Location: Austria
  • Views: 1387
  • Message 170 of 411

Re: TPT2 has USB port power issue

2013-01-28, 15:23 PM

Well said Patanjali!

 

Building a device that lives dead on the limits of specs can be considered suicidal :smileywink:

 

Since customers usually do NOT and should NOT HAVE TO care about production tolerances but expect that one certified devices will work together with another certified device, it's up to the OEMs to be well over or under spec limits.

 

Producers of power drawing devices are well adviced to keep the average (over each single entity of that device type) power consumtion below the minimum spec (4.75V * 500mA = 2.375W) allowing for a production tolerance of +5%, still ending below the nominal limit of 2,5W at 5V at 500mA.

Power sourcing devices should be built to supply the upper end of the spec range (5,25V * 500mA = 2,625W) allowing for -5% tolerance and still maintaining nominal 2,5W at 5V at 500mA.

 

Any product exceeding this +5% OR -5% tolerance runs the risk to fail with any other product, even if the other one lives within its respective +5% or -5% tolerance!

 

Tolerances are not there to be used up deliberately, but to allow for inevitable fluctuations of production factors (components, work force, environmental influence, ...).

 

If TPT2 would have been built in respect to this QA principle, there might be only few TPT2s that have this problem and even less devices that would not work with those. But since this seems to be a problem with most of the TPT2s in connection with most of devices that don't cause problems connected to power sourcing devices, I'd say Lenovo has not understood the specs in the way they were intended to be understood.

Or they knew about this hickup and still yielded devices that should have faild QA. Or even worse, they acually failed and still have been marked "PASS" to increase output and profit, hoping that noone will notice.

 

BUT WE HAVE!!!!!

 

 

Reply
Forum Home

Community Guidelines

Please review our Guidelines before posting.

Learn More

Check out current deals!

Go Shop
X

Save

X

Delete

X

No, I don’t want to share ideas Yes, I agree to these terms