PCB Stack Impedance issue

[huypq6]

Hi there,
I am preparing to design an iMX6UL development kit.
My PCB stack is 4 layer.

L1 (signal)
L2 (GND)
L3 (POWER)
L4 (signal)

Should i have to control impedance on both of layer when routing DDR3? Assume that the track what has 50Ohm impedance in layer 1 is 0.12 mm width, but 0.12mm track is not 50Ohm impedance in layer 4. So that what will i have problem if i route 0.12mm track for DDR3 signal in layer 4?

Thank you for your help!

[mairomaster]

You definitely need impedance control on all layers where you are routing DDR3 signals. L4 will normally use the L3 power layer as a reference, so you should be having the same track parameters.

Despite the reference design for iMX6UL from NXP being done on 4 layers (if I remember correctly), this puts some limitations on what you can do on the board and will be quite challenging as well, if you don't have much experience designing such boards.

[robertferanec]

I agree with mairomaster.

PS: This iMX6UL design confused a lot of people. If you would like to use POWER as a reference plane, be sure there are a lot of decoupling capacitors between the plane and GND and also be sure this plane is above all the memory tracks.

[huypq6]

Thank you mairomaster and robertferanec,
Exactly, the reference layout is 4 layers. I checked reference layout and reference design and i did not find some decoupling capacitor such C101, C102. I guest that it was be removed.

This is my very first high speed design. So that i will try to route with 6 layers PCB. Base on robertferanec 's guide in his course, I define my PCB stack like attachment.

Do you have any comment for my further work?

[robertferanec]

6 layers could help. Be sure you know track geometry on top and bottom layer for all the impedances you need. Double check the stackup and impedances with your PCB manufacturer.

[huypq6]

robertferanec Thank you, I worked with 8 layers.

[huypq6]

i got the pcb.
Now, i have trouble while debug it. I used Mfg tool from NXP.
when i upload uboot into kit, i received error about initializing memory. Below is MFG log and config. Pls, give me some advice in this case.

MFG log

DLL version: 2.6.2
Friday, June 30, 2017 10:22:44   Start new logging
ModuleID[2] LevelID[10]: CMyExceptionHandler thread is running
ModuleID[2] LevelID[1]: new MxHidDeviceClass
ModuleID[2] LevelID[10]: new MxHidDevice[04718FB8]
ModuleID[2] LevelID[1]: new MxHidDeviceClass
ModuleID[2] LevelID[10]: new MxHidDevice[04719488]
ModuleID[2] LevelID[1]: new MxHidDeviceClass
ModuleID[2] LevelID[10]: new MxHidDevice[047BF6D8]
ModuleID[2] LevelID[1]: new MxHidDeviceClass
ModuleID[2] LevelID[10]: new MxHidDevice[04819050]
ModuleID[2] LevelID[1]: new MxHidDeviceClass
ModuleID[2] LevelID[10]: new MxHidDevice[04842A38]
ModuleID[2] LevelID[1]: new MxHidDeviceClass
ModuleID[2] LevelID[10]: new MxHidDevice[0483D730]
ModuleID[2] LevelID[10]: Device Manager thread is running
ModuleID[2] LevelID[1]: Can't set m_hStopEvent before it initialized or it already stop

ModuleID[2] LevelID[10]: CmdOperation[0] device chagned and reset to state 0
ModuleID[2] LevelID[10]: CmdOperation[0], skip current command, so SetEvent(hDevCanDeleteEvent)
ModuleID[2] LevelID[10]: CmdOperation[0], skip current command, so SetEvent(hDevCanDeleteEvent)
ModuleID[2] LevelID[10]: CmdOperation[0], skip current command, so SetEvent(hDevCanDeleteEvent)
ModuleID[2] LevelID[10]: CmdOperation[0], skip current command, so SetEvent(hDevCanDeleteEvent)
ModuleID[2] LevelID[10]: CmdOperation[0], skip current command, so SetEvent(hDevCanDeleteEvent)
ModuleID[2] LevelID[10]: ExecuteCommand--Boot[WndIndex:0], File is C:\Users\Huypq6\Downloads\L4.1.15_1.0.0_ga-mfg-tools.tar\L4.1.15-1.0.0_ga-mfg-tools\mfgtools\Profiles\Linux\OS Firmware\firmware\u-boot-imx6ul14x14ddr3arm2_sd.imx
ModuleID[2] LevelID[1]: MxHidDevice::Write() Error writing to device 0x1f.
ModuleID[2] LevelID[1]: Failed to initialize memory!
ModuleID[2] LevelID[1]: PortMgrDlg(0)--MxHidDevice--Command Boot excute failed
ModuleID[2] LevelID[10]: CmdOperation[0], current command executed failed, so SetEvent(hDevCanDeleteEvent)
ModuleID[2] LevelID[10]: ExecuteCommand--Boot[WndIndex:0], File is C:\Users\Huypq6\Downloads\L4.1.15_1.0.0_ga-mfg-tools.tar\L4.1.15-1.0.0_ga-mfg-tools\mfgtools\Profiles\Linux\OS Firmware\firmware\u-boot-imx6ul14x14ddr3arm2_sd.imx
ModuleID[2] LevelID[1]: MxHidDevice::Write() Error writing to device 0x1f.
ModuleID[2] LevelID[1]: Failed to initialize memory!
ModuleID[2] LevelID[1]: PortMgrDlg(0)--MxHidDevice--Command Boot excute failed
ModuleID[2] LevelID[10]: CmdOperation[0], current command executed failed, so SetEvent(hDevCanDeleteEvent)
ModuleID[2] LevelID[10]: ExecuteCommand--Boot[WndIndex:0], File is C:\Users\Huypq6\Downloads\L4.1.15_1.0.0_ga-mfg-tools.tar\L4.1.15-1.0.0_ga-mfg-tools\mfgtools\Profiles\Linux\OS Firmware\firmware\u-boot-imx6ul14x14ddr3arm2_sd.imx
ModuleID[2] LevelID[1]: MxHidDevice::Write() Error writing to device 0x1f.
ModuleID[2] LevelID[1]: Failed to initialize memory!
ModuleID[2] LevelID[1]: PortMgrDlg(0)--MxHidDevice--Command Boot excute failed
ModuleID[2] LevelID[10]: CmdOperation[0], current command executed failed, so SetEvent(hDevCanDeleteEvent)
ModuleID[2] LevelID[10]: ExecuteCommand--Boot[WndIndex:0], File is C:\Users\Huypq6\Downloads\L4.1.15_1.0.0_ga-mfg-tools.tar\L4.1.15-1.0.0_ga-mfg-tools\mfgtools\Profiles\Linux\OS Firmware\firmware\u-boot-imx6ul14x14ddr3arm2_sd.imx
ModuleID[2] LevelID[1]: MxHidDevice::Write() Error writing to device 0x1f.
ModuleID[2] LevelID[1]: Failed to initialize memory!
ModuleID[2] LevelID[1]: PortMgrDlg(0)--MxHidDevice--Command Boot excute failed
ModuleID[2] LevelID[10]: CmdOperation[0], current command executed failed, so SetEvent(hDevCanDeleteEvent)
ModuleID[2] LevelID[10]: DeviceManager::DevChangeWnd::OnDeviceChange() - DEVICE_REMOVAL_EVT(\\?\USB#VID_15A2&PID_007D#6&106a4439&0&2#{a5dcbf10-6530-11d2-901f-00c04fb951ed})
ModuleID[2] LevelID[10]: DeviceManager::DevChangeWnd::OnDeviceChange() - end
ModuleID[2] LevelID[10]: DeviceManager::OnMsgDeviceEvent() - DEVICE_REMOVAL_EVT(\\?\USB#VID_15A2&PID_007D#6&106a4439&0&2#{a5dcbf10-6530-11d2-901f-00c04fb951ed})
ModuleID[2] LevelID[10]: DeviceClass::FindDeviceByUsbPath--DeviceListType_Current, _devices.size: 1
ModuleID[2] LevelID[10]: DeviceClass::FindDeviceByUsbPath--DeviceListType_Current, devInstPathToFind: USB\VID_15A2&PID_007D\6&106A4439&0&2, _deviceInstanceID: USB\VID_15A2&PID_007D\6&106A4439&0&2
ModuleID[2] LevelID[10]: DeviceClass::FindDeviceByUsbPath--DeviceListType_Current, Find the device
ModuleID[2] LevelID[10]: DeviceManager::OnMsgDeviceEvent() - DEVICE_REMOVAL_EVT,[MxHidDeviceClass] vid_15a2&pid_007d, Hub:6-Port:2
ModuleID[2] LevelID[10]: DeviceManager::OnMsgDeviceEvent() - DEVICE_REMOVAL_EVT, Notify
ModuleID[2] LevelID[10]: CmdOpreation[0]--OnDeviceChangeNotify, Volume Arrive/Remove or Device Arrive/Remove
ModuleID[2] LevelID[10]: CmdOpreation[0]--OnDeviceChangeNotify, m_p_usb_port is not NULL, so only refresh
ModuleID[2] LevelID[10]: CmdOpreation[0]--OnDeviceChangeNotify, Volume/Device Remove
ModuleID[2] LevelID[1]: CmdOpreation[0]--set m_hDeviceRemoveEvent.
ModuleID[2] LevelID[10]: CmdOpreation[0]--WaitforEvents device remove1
ModuleID[2] LevelID[10]: DeviceManager::OnMsgDeviceEvent()-DEVICE_REMOVAL_EVT, hDevCanDeleteEvent has been set
ModuleID[2] LevelID[10]: delete MxHidDevice[0483D730]

MFG config

[profiles]
chip = Linux

[platform]
board = SabreSD[LIST]
name = SDCard

[variable]
board = sabresd
mmc = 0
sxuboot=sabresd
sxdtb=sdb
7duboot=sabresd
7ddtb=sdb
6uluboot=14x14ddr3arm2
6uldtb=14x14-ddr3-arm2
ldo=
plus=
initramfs=fsl-image-mfgtool-initramfs-imx_mfgtools.cpio.gz.u-boot
seek = 1
sxnor=qspi2
7dnor=qspi1
6ulnor=qspi1
nor_part=0

[robertferanec]

I am not sure. I do not use latest MFG tools. I use this: http://www.imx6rex.com/open-rex/soft...setup-mfgtool/