Power Supply Info

From DD-WRT Wiki

(Difference between revisions)
Jump to: navigation, search
Revision as of 23:12, 1 July 2009 (edit)
Donny (Talk | contribs)
m (New page: Here is a page for putting power supply info on....)
← Previous diff
Current revision (18:08, 16 November 2017) (edit) (undo)
Ian5142 (Talk | contribs)

 
(9 intermediate revisions not shown.)
Line 1: Line 1:
-Here is a page for putting power supply info on....+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 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)