Adam Wang wrote: > See Q3 with D1 in circuit: > http://downloads.qi-hardware.com/people/adam/m1/tmp/m1r4/Misc_led_20120202.pdf
Looks good, except that R229 works against the pull-up in the FPGA, which probably works but looks a bit ugly. How about making R229 a pull-up, too ? By the way, PWM for D41/D42 is only an idea in case we need to dim the LEDs. If we don't need that, they could just be always on or off, like in M1rc3. > 1). R41 = 120 Ohm That would be very bright :-) > D1 is fully ON, If = Ids = 9.67mA when I simulated LED_PWR net(i.e. gate > pin of Q3) to connect 3.3V net [ simulated a pullup ] How did you simulate ? Qucs ? > 2). R41 = 560 Ohm > D1 ON, If = Ids = 2.446mA, 3.3V on gate pin [ a pullup ] Looks good. ~2.5 mA is also what I got in my measurements with LTST-C190KRKT. > D1 OFF, 0 uA [ a pulldown ] Well, technically it would be a "strong drive". > 3). PWM test, don't know how to test it since my current weakness on f/w. You would have to write a bit of Verilog :-) It would be easy (much simpler than the LED matrix controller), but as I said, we may not even need this. > 4). off-ledm, R42 drew with a 560 Ohm. Good. > dark --> no power/disabl , do you know which current pulled out fpga pin Nominally zero ? Not sure if I understood the question. > so I think that I need to detemine R41 value from your current flow of > LTST-C190KRK (off-ledm circuit example from circuit R42 you there), then I > fine trun same current with resistance (my site here) to get an expected > brightness. > How do you think? Yes, sounds good. I just saw that I have a few APT1608SURCK. That's the same junction as in the diode we want to M1r4. Maybe I'll give it a try ... > for off-ledm, [...] Hmm, easy to misread as "off-LED", which would be confusing :) > [...] two leds D1 [DC-in] and D2 [Booted], according chat in irc, I > drew them for: > a). on-ledm, R200 ~ R203 marks as 270 Ohm > b). off-ledm, R41, TBD > c). off-ledm, R42, 560 Ohm If Q3.Rds(on) << R41, then R41 should be equal to R42. And, given the date we have so far, both should be around 560 Ohm. I.e., you can change "TBD" to "560 Ohm" :) - Werner _______________________________________________ http://lists.milkymist.org/listinfo.cgi/devel-milkymist.org IRC: #milkymist@Freenode
