Hi everyone,
I am going through initial powerup on a cape I designed, and I have one thing misbehaving: the battery backup circuit. I have the simple circuit depicted below, where the battery is a li=ion cell in a battery clip on the cape. <https://lh5.googleusercontent.com/-rG_KhXfNzNc/VCqdi9UzyuI/AAAAAAAAACE/xdCnm6U_QQ8/s1600/bat.png> What I have found is that the board will not power up if the battery is absent. I get brief flashes on the power LED as if it were overloaded. Experimenting with the BeagleBone with no cape installed, I found that if I installed a 10k resistor between GND (TP8) and TS (TP7) , and a jumper between BAT1/2 (TP5) and BAT_SENSE (TP6), I got the same behavior. This behavior is present when powered from either USB or VDD_5V via P9. If I install the battery, the board powers up. If I remove the jumper, the board powers up. In fact, if I install a 10k pulldown between BAT1/2/SENSE and GND, the board powers up. In the TPS65217C datasheet, it implies that an absent battery should not be a problem - but does "absent battery" also mean that BAT_SENSE must be disconnected from BAT1/2? Or could this be an issue with the rise time of my 5VDC coming in? I don't think this is the case since it does the same thing when plugged in to USB power. Any insight would be much appreciated! -Nate -- 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.
