• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 369 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Power management forum

KLP KLP
Prodigy 60 points
Part Number: TPS23881
Other Parts Discussed in Thread: TPS23882B, TPS23882, TPS23880, , TPS23841, TPS2384, TPS23861

Hi, 

Good morning. Our objective is to incorporate PoE to our device. Our use case is such that our device could connect to a single class 1 PD (4W max). We have run through selection guide but could not come to a firm decision on which component to use. So far our selections shows that most of the PSE controller allow connections to 4 and 8 PSE ports.

Would like advice on the follow questions -

1. Is there a PSE controller with a single PSE port?

2. How do we know if we should use 2 pairs or 4 pairs control? Since our target PD is a low power sensor of Class 1, it should not require 4 pairs. However, we could not confirm if the target PD is using either Pair 1-2. 3-6 OR Pair 4-5, 7-8. My reading shows that Endspan is based on Pair 1-2, 3-6 while Midspan Pair 4-5, 7-8. How do we design in such a way that we could cater for PD that uses Midspan or Endspan? Analog Devices seems to have a different definition of Midspan. 

3. Would using a PSE controller for 4 pairs cater for PD that either uses Mid Span or Endspan?

4. What are the considerations of using TPS23882B in place of TPS23882? 

5. What are the considerations of using TPS23881 in place of TPS23880?

6. The pricing for TPS23841 is very expensive at USD6.60. Is this an old chip?

7. TPS2384 is bigger and more expensive than TPS23882B. Is this a recommended chip as well?

8. TPS23861 is the cheapest among them all and with autonomous mode as well. Any concerns on using this chip?

Any information is much appreciated on this. 

Best rgds,

Pang

  • 0
    TI__Genius 15685 points

    Hi Pang,

    Sorry for my delayed response. Please see my answers below. 

    1. Is there a PSE controller with a single PSE port?

    [PX]No.

    2. How do we know if we should use 2 pairs or 4 pairs control? Since our target PD is a low power sensor of Class 1, it should not require 4 pairs. However, we could not confirm if the target PD is using either Pair 1-2. 3-6 OR Pair 4-5, 7-8. My reading shows that Endspan is based on Pair 1-2, 3-6 while Midspan Pair 4-5, 7-8. How do we design in such a way that we could cater for PD that uses Midspan or Endspan? Analog Devices seems to have a different definition of Midspan. 

    [PX]Alt A and Alt B both are OK for mids-span applications according to the latest IEEE standard. 

    3. Would using a PSE controller for 4 pairs cater for PD that either uses Mid Span or Endspan?

    [PX]You don't need to. The PDs are required to be able to receive power from either Alt A or Alt B pairs. PSE has the option to choose sending power through Alt A or Alt B. 

    4. What are the considerations of using TPS23882B in place of TPS23882? 

    [PX]Both TPS23882 and TPS23882B are active devices and TPS23882B has autonomous mode and doesn't need SRAM patch to be loaded after power up. 

    5. What are the considerations of using TPS23881 in place of TPS23880?

    [PX]TPS23881 is a newer generation compared to TPS23880 and we will recommend TPS23881 as it has reduced Rsense to improve system efficiency. 

    6. The pricing for TPS23841 is very expensive at USD6.60. Is this an old chip?

    [PX]Yes. TPS2384 is an old device. 

    7. TPS2384 is bigger and more expensive than TPS23882B. Is this a recommended chip as well?

    [PX]We always recommend newer devices for new designs. 

    8. TPS23861 is the cheapest among them all and with autonomous mode as well. Any concerns on using this chip?

    [PX]TPS23861 is cost optimized for lower port count systems as well as systems without I2C bus available for PSE chip. 

    Thanks. 

    Penny

  • 0 in reply to Penny Xu
    Prodigy 60 points

    Dear Penny, 

    Happy Chinese New Year to you and thanks for the reply. 

    Further questions.

    How shall we choose between TPS23882B and TPS23861 considering we are just a device with a single Ethernet port connecting to a PD of Type 1 PoE? Can I assume TPS23861 fully adequate?

    Thanks.

    Best rgds,

    Pang

  • +1 in reply to KLP KLP
    TI__Genius 15685 points

    Hi Pang,

    TPS23861 should be good enough for your application. Thanks!

    Best regards,

    Penny