Power Supply Info
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- | I | + | I don't know why but linksys looks like they like starving their Wireless Routers and AP's of POWER. |
- | + | They supply you with a .5 to 1.5 amp switching power supply way under what you need . | |
- | + | Look a the product spec sheet for a WPC300N PCMCIA WiFi card; | |
- | + | ||
Power Consumption | Power Consumption | ||
TX: <900mA (Maximum) | TX: <900mA (Maximum) | ||
RX: <700mA (Maximum) | RX: <700mA (Maximum) | ||
- | http://downloads.linksysbycisco.com/downloads/WPC300N_ds,0.pdf | ||
+ | [http://downloads.linksysbycisco.com/downloads/WPC300N_ds,0.pdf http://downloads.linksysbycisco.com/downloads/WPC300N_ds,0.pdf] [broken] | ||
+ | |||
+ | |||
+ | Look at what the BCM4705 CPU Power Consumption is; | ||
+ | 5v @ 2.4w = 0.48 amp just under 1/2 amp. | ||
+ | |||
+ | [http://www.broadcom.com/collateral/pb/4705-PB01-R.pdf http://www.broadcom.com/collateral/pb/4705-PB01-R.pdf] [broken] | ||
- | + | the switch BCM 5325 Power Consumption is 5v 1.4W = 0.28 amp | |
- | + | ||
+ | [http://www.broadcom.com/collateral/pb/5325-PB05-R.pdf http://www.broadcom.com/collateral/pb/5325-PB05-R.pdf] | ||
- | + | also add the RAM power consumption (unknown at this time) | |
- | + | ||
- | + | Remember the variation that is needed; normally 5% to 10% | |
- | + | Power needed just for this item at minimum so far: | |
- | + | 900 ma | |
+ | 270 ma | ||
+ | 480 ma | ||
+ | total: 1650 ma which equals 1.65 amp | ||
- | + | Other Routers have this problem too!! | |
- | + | This is a thread were you can find out More Info if you need: [http://www.dd-wrt.com/phpBB2/viewtopic.php?t=54242&postdays=0&postorder=asc&start=0 DD-Wrt Forum] | |
- | + | ---- | |
+ | Engineer's comment:<br /> | ||
+ | I'm not refuting the fact that they could very well be power starved, I just want to clear up a misconception of the original author. | ||
- | + | What is important here is the sum of the POWERS not the sum of the currents. | |
+ | Switching power supplies, are very efficient at converting voltage/current levels; and if properly designed can reach efficiencies of 95%.<br /> | ||
- | + | Using the values provided above, and assuming a Vbus of 3.3v:<br /> | |
+ | 1.65a * 3.3v = 5.45w | ||
- | + | The router needs at least 5.45w to operate correctly. | |
- | + | Now let's look at the wall wort.<br /> | |
+ | 12v output, at 500ma = 6watts.<br /> | ||
+ | factoring in the inefficiencies of the power supply on the router, it is obvious that we are running at the limit of the wall wort. | ||
- | + | Recommendation: if you have a 12v/500ma adapter with your router, seriously consider getting a new one. | |
+ | Get an adapter rated for at least 1a at 12v and you should be fine. | ||
- | + | --[[User:Dejagerd|Dejagerd]] 03:26, 19 February 2010 (CET) | |
- | + | [[Category:Linksys]] | |
+ | [[Category:Hardware]] |
Current revision
I don't know why but linksys looks like they like starving their Wireless Routers and AP's of POWER. They supply you with a .5 to 1.5 amp switching power supply way under what you need . Look a the product spec sheet for a WPC300N PCMCIA WiFi card;
Power Consumption TX: <900mA (Maximum) RX: <700mA (Maximum)
http://downloads.linksysbycisco.com/downloads/WPC300N_ds,0.pdf [broken]
Look at what the BCM4705 CPU Power Consumption is;
5v @ 2.4w = 0.48 amp just under 1/2 amp.
http://www.broadcom.com/collateral/pb/4705-PB01-R.pdf [broken]
the switch BCM 5325 Power Consumption is 5v 1.4W = 0.28 amp
http://www.broadcom.com/collateral/pb/5325-PB05-R.pdf
also add the RAM power consumption (unknown at this time)
Remember the variation that is needed; normally 5% to 10%
Power needed just for this item at minimum so far: 900 ma 270 ma 480 ma total: 1650 ma which equals 1.65 amp
Other Routers have this problem too!!
This is a thread were you can find out More Info if you need: DD-Wrt Forum
Engineer's comment:
I'm not refuting the fact that they could very well be power starved, I just want to clear up a misconception of the original author.
What is important here is the sum of the POWERS not the sum of the currents.
Switching power supplies, are very efficient at converting voltage/current levels; and if properly designed can reach efficiencies of 95%.
Using the values provided above, and assuming a Vbus of 3.3v:
1.65a * 3.3v = 5.45w
The router needs at least 5.45w to operate correctly.
Now let's look at the wall wort.
12v output, at 500ma = 6watts.
factoring in the inefficiencies of the power supply on the router, it is obvious that we are running at the limit of the wall wort.
Recommendation: if you have a 12v/500ma adapter with your router, seriously consider getting a new one. Get an adapter rated for at least 1a at 12v and you should be fine.
--Dejagerd 03:26, 19 February 2010 (CET)