The BBB requires a very stable supply. The spec is 5.0 Volts plus/minus 0.25 Volts under all loads, none to maximum. If the supply, as viewed at the BBB PMC, goes above 5.5 or below 4.6 for even a few milliseconds, the PMC will go into protective shutdown. Put a scope on the power leads and make sure your supply can stay inside the specifications, while the load is jumping around. --- Graham
== On Friday, February 19, 2016 at 8:42:12 PM UTC-6, john3909 wrote: > > Yep, a linear regulator will cook with a BBB attached. Assuming the BBB > consumes 1A, then you will dissipate (25v - 5v) * 1A = 20Watts. This > regulator cannot handle that power dissipation and will die. Better to use > a switching regulator which has an efficiency of around 90% or better. > > > Regards, > John > > > > > On Feb 19, 2016, at 5:15 PM, Rizalino Antonio de Guzman < > [email protected] <javascript:>> wrote: > > given that my source voltage is 25V, i assumed that i should scale up this > resistor. ill give that a try next time. Thank you > > Rizalino de Guzman > > On Feb 19, 2016, at 6:06 PM, Bill Pretty <[email protected] > <javascript:>> wrote: > > Looking at your schematic, I believe that 1K is too large a value. It > should be about 240 ohms and R2 should be scaled accordingly. It could be > that the LM317 is taking too long to stabilize. You will notice that the > application circuit provided by the data sheet uses a 240 ohm resistor. > > *From:* [email protected] <javascript:> [ > mailto:[email protected] <javascript:>] *On Behalf Of *Rizalino > de Guzman > *Sent:* Friday, February 19, 2016 7:06 PM > *To:* BeagleBoard > *Subject:* [beagleboard] Custom Power Supply > > Hello, > I am currently trying to build a power supply based on an LM317 to provide > different voltage outputs, powered by a single voltage source. One of the > loads is a Beaglebone Black. I'm curious as to why my beaglebone black does > not turn on even when my p/s output is a steady 5V (give or take. my > simulations show 4.6V while my actual circuit produces around 5.3V). I'm > attaching a schematic of my LM317 power supply. When I hook up the > beaglebone on a DC power supply, it turns on. Any help would be > appreciated. Thanks! > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > For more options, visit https://groups.google.com/d/optout. > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > For more options, visit https://groups.google.com/d/optout. > > > -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected] <javascript:>. > For more options, visit https://groups.google.com/d/optout. > > > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
