Ron K. Jeffries wrote: > 1) What's your estimate of the (approx) max power draw > that is safe when external Ben Dongle leeches power from Ben?
Heh, I knew this question would come :-) I don't really know. But let's see what the limits are along the path: First, Q4, next to the 8:10 card slot: it's a TM2301FN [1] with a Ron of about 0.1 Ohm and a maximum current of 2.3 A. So it's not really an obstacle for anything. Q4 is supplied from +V3.3, which comes from the U2 regulator, an EUP3406 [2]. It has a nominal output current of 600 mA, peak 800 mA. Again, quite a high limit. The schematics say the inductor L1 is rated at 1 A, so it should be good for a regulator output current of about 833 mA. Q4 is supplied from +VBAT. If USB-powered, +VBAT is fed via D2 from +VUSB. D2 is an MSCD104 [3] with a maximum average current of 1 A. +VUSB passes through BD6, a PZ1608D221TF [4], which the data sheet rates at 800 mA (Adam, [6] shows a rating of 1 A ?). Of course, you could have looked up all this yourself with schematics [5] and the data sheet links in the inventory [6] :-) [1] http://downloads.qi-hardware.com/hardware/qi_avt2/v1.0/datasheet/Q1_2_4_6_11~TM2301FN.pdf [2] http://downloads.qi-hardware.com/hardware/qi_avt2/v1.0/datasheet/U2_3~EUP3406.pdf [3] http://downloads.qi-hardware.com/hardware/qi_avt2/v1.0/datasheet/D1_2_4_5_6~MSCD104H.pdf [4] http://downloads.qi-hardware.com/hardware/qi_avt2/v1.0/datasheet/BD2_3_6_7_8_9_10~PZ1608D221.pdf [5] http://en.qi-hardware.com/w/images/9/9c/Lb60_schematic.pdf [6] http://en.qi-hardware.com/wiki/Sharism_inventory So if the upstream port can handle it, the Ben can draw a maxmimum of about 600 mA at its 3.3 V rail if the other rails have no significant load. I don't know the Ben's own peak consumption, but I would estimate it's below 200 mA. So you may be able to draw up to 400 mA, provided that your upstream USB port can handle it. I wouldn't recommend to design things to go over 100 mA, which would leave a 500 mA port with ~100 mA for the 8:10 card (a bit less), maybe 200 mA for the total Ben, 110 mA for charging the battery, and a bit of tolerance. Unfortunately, there is no proper current limiter in the path. But nothing bad happened on those occasions when I accidently shorted 8:10 card power. > 2) Given recently discovered lower than optimal power > to Ben from external charger during Ben operation > (not an issue when Ben is powered down) what do you estimate > to be a steady state allowable dongle power draw that will > not cause battery to discharge? The low charge current limit only has a peripheral effect on the current available at the 8:10 card interface. After all, the charge current goes to the battery, not the 8:10 card. However, the battery would start discharging if you overload the USB upstream port to the point of it shutting down. > p.s. I hope you appreciate my suggested > OLD ubb = "universal breakout board" > NEW UBbb = "Universal Ben breakout board." I very much hope at even its successor would offer the same interface. So it would have to be something like the Universal NanoNote Breakout Board, UNNBB, which seems a little awkward. If you like triplicate letters, you'll appreciate the naming of my helper library: http://projects.qi-hardware.com/index.php/p/wernermisc/source/tree/master/libbb But I assure you, typing libbbd.c a lot of times or spotting the typo when you get a "no such file" can drive you nuts ... - Werner _______________________________________________ Qi Hardware Discussion List Mail to list (members only): [email protected] Subscribe or Unsubscribe: http://lists.en.qi-hardware.com/mailman/listinfo/discussion
