P1<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
---<br>
<br>
B1, B2, B3 - call +1.5V "DRAM_VCC" and +0.75V "DRAM-REF", then put 1<br>
of the capacitors connected directly to the DRAM-REF, and mark it<br>
"keep as close to DDR3 as possible", to remind yourself. joe will<br>
know what value those need to be, but that ref voltage *must* be kept<br></blockquote><div><br>All the decoupling capacitors kept on one sheet for ease of handling, will note it down in the schematic about the critical positions. Joe is going to attempt a layout. Could you give some suggestions regarding layers, the ones to be dedicated for ground etc. My understanding is that there should be s ground layer next to the DDR3 tracks to get the characteristic impedance correct and also to give good return path. Something like:<br>
L1 : tracks , L2 : ground, L3 : power, L4 : tracks, L5 : GND, L6 : tracks<br>Since you already have done it, please make some concrete suggestions on that.<br></div><div><br> </div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
A6, A7 - 24mhz XTAL is connected to RTC :) that'll need to be to N23<br>
and N22 :) then, if you are going to have an RTC, you *need* that<br>
32mhz crystal - you cannot leave it off. remember the 10M/1% resistor<br>
which needs to be put in parallel with the 32mhz XTAL.<br></blockquote><div><br>That was a mistake, intention is to use only the 24MHz oscillator, not the 32k one. Corrected.<br><br></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
E4, E5 - if the SY8008C is the same as the SY8008B, then you want<br>
resistors 10x that size, and you want them @ 1%. so: R10 = 150K/1%,<br>
R11 = 100K/1%, and R13 = 442K/1% and R16 = 100K/1%.<br></blockquote><div><br>SY8008B or C would do 1A and 1.2A, the resistors calculated as per the data book. Olinuxino seems to be using 1.1K and 4.99K, I thought it is too much of current wasted and used higher values. 100k & 1500k will make the feedback path current 4 micro amps, will it make it more prone to noise. Should I change it ?<br>
</div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
also you're missing the capacitors which *must* be close to the SY8008<br>
- you want a 10uF on the IN as well as the OUT, but also on the OUT<br>
you want a 2nd much *smaller* capacitor (joe - 0.1uF?) as this catches<br>
the high frequencies. make sure you put these as connected directly<br>
to the SY8008 because that tells you, when you come to do the layout,<br></blockquote><div><br>The instructions for layout will be marked in the schematic, so that is it is not overlooked. <br><br><br></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
to each and every single pin. my recommendation here: follow the<br>
example schematic on p5 of the AXP209 datasheet.<br></blockquote><div><br>I did not find an English version, learned somewhat from a lower version AXP202.<br> <br></div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
C7 - what's the 6-pin thing connected to DM0/DP0? it's not marked.<br></blockquote><div><br>Another mistake, it is only a USB header with two shield pins. Corrected.<br><br> </div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
other comments:<br>
<br>
* no JTAG! no JTAG+UART equals very very baaad :)<br></blockquote><div><br>Should I add a 20 pin JTAG connector or just bring TDI0, TDO0, TMS0, TCK0 and RESET to a header. Please suggest.<br><br><br>with regards<br><br>
Ajith<br><br><br> </div><blockquote class="gmail_quote" style="margin:0pt 0pt 0pt 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
* joe, what you reckon - a 5V Zener diode on VUSB near the CPU? VUSB's<br>
range is +4.75 to +5.25. put a BZT52C5V1S from VUSB to GND?<br>
<br>
/peace<br>
<br>
l.<br>
<br>
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</blockquote></div><br><br clear="all"><br>-- <br>Dr. Ajith Kumar B.P.<br>Scientist SH<br>Inter-University Accelerator Centre<br>Aruna Asaf Ali Marg<br>New Delhi 110067<br><a href="http://www.iuac.res.in/" target="_blank">www.iuac.res.in</a><br>
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