Power Supply Info

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Revision as of 02:26, 19 February 2010 (edit)
Dejagerd (Talk | contribs)
(misconception is commented on.)
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Ian5142 (Talk | contribs)

 
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-I dont know why but linksys looks like they like starving their Wireless Routers and AP's of POWER.+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 . 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; Look a the product spec sheet for a WPC300N PCMCIA WiFi card;
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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; Look at what the BCM4705 CPU Power Consumption is;
5v @ 2.4w = 0.48 amp just under 1/2 amp. 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 http://www.broadcom.com/collateral/pb/4705-PB01-R.pdf] [broken]
the switch BCM 5325 Power Consumption is 5v 1.4W = 0.28 amp 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 http://www.broadcom.com/collateral/pb/5325-PB05-R.pdf]
also add the RAM power consumption (unknown at this time) also add the RAM power consumption (unknown at this time)
-Remember the varation that is needed; normaly 5% to 10%+Remember the variation that is needed; normally 5% to 10%
Power needed just for this item at minimum so far: Power needed just for this item at minimum so far:
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total: 1650 ma which equals 1.65 amp total: 1650 ma which equals 1.65 amp
-Other Routers have this problem to!! +Other Routers have this problem too!!
-This is a thread were you can find out More Info if you need .+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]
-http://www.dd-wrt.com/phpBB2/viewtopic.php?t=54242&postdays=0&postorder=asc&start=0+
---- ----
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Recommendation: if you have a 12v/500ma adapter with your router, seriously consider getting a new one. 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. Get an adapter rated for at least 1a at 12v and you should be fine.
 +
--[[User:Dejagerd|Dejagerd]] 03:26, 19 February 2010 (CET) --[[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)