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Recent content by jamesnguyen

  1. jamesnguyen

    Looking for Memec Design's DS-BD-V4LX25LC schematic

    I found it. Thank you anyway https://www.em.avnet.com/en-us/design/drc/Pages/SupportAndDownloads.aspx?RelatedId=143
  2. jamesnguyen

    Looking for Memec Design's DS-BD-V4LX25LC schematic

    Hi, A friend of mine gave me the Memec Design's DS-BD-V4LX25LC FPGA board. It has a Xilinx's Vertex 4 XC4VLX25 on it. He doesn't have the schematic anymore and I also can't find anything on the web. Does anyone know where I can get a copy? Thanks, James
  3. jamesnguyen

    PC resets when its USB port is connected to a portable device on charger

    Is there such an AC/DC wall adapter with the DC ground earth grounded? Most wall adapters out there have 2 prongs. Some has 3 prongs but the DC ground is isolated from earth grounded. James
  4. jamesnguyen

    PC resets when its USB port is connected to a portable device on charger

    When I connect 100 kohms between the two grounds, they are at the same potential. As soon as the 100k resistor is disconnected, the charger's "ground" voltage starts to drift. Neither system resets when I earth grounded the charger's ground, but I don't think it's practical or safe. James
  5. jamesnguyen

    PC resets when its USB port is connected to a portable device on charger

    Hi, My company makes a portable device (battery operated). If we connect the device's USB port to a PC while it sits on the charger, sometimes device resets, sometimes the PC reset, sometimes both reset. I think the problem is caused by the voltage differential between the grounds of the two...
  6. jamesnguyen

    Interfacing 3.3V device to a 1.8V parallel bus

    Anyone?
  7. jamesnguyen

    Interfacing 3.3V device to a 1.8V parallel bus

    Hi, On my existing design, the Processor's External Bus Interface (EBI) is currently interfacing to a SDR SDRAM chip. The bus runs on 1.8V @ 130 MHz. Now, I need to add a device to the EBI, but unfortunately, this device requires 3.3V to run. Besides the obvious level translation IC, do I...
  8. jamesnguyen

    USB OTG without USB ID pin?

    Hi, I have a USB OTG capable device. Unfortunately, the USB ID pin is not brought out to the connector (it's floating). Is the USB ID pin required for OTG function? Let's suppose my device somehow knows the Host/Device role it is supposed to be (by other means), would USB OTG function, in...
  9. jamesnguyen

    4-bit ECC NAND on 1-bit ECC Processor

    Thank you so much!
  10. jamesnguyen

    4-bit ECC NAND on 1-bit ECC Processor

    Hi, We have an old Processor, which have a hardware support 1-bit ECC NAND Flash. We now have to upgrade our NAND Flash IC and unfortunately, almost all newer NAND Flash ICs require 4-bit ECC. How does our Processor, which only have 1-bit ECC support, work with a 4-bit ECC NAND Flash part...
  11. jamesnguyen

    DDR memory signal integrity simulation

    Thank you so much! Is there any tutorial on how to simulate the DDR memory?
  12. jamesnguyen

    DDR memory signal integrity simulation

    Hi, I am doing a design with DDR memory and I need to simulate the signal integrity of the PCB layout. Yes, I have never done SI check for the DDR memory before, so I don't know anything... How do I find out the information such as voltage requirements (overshoot, undershoot, etc), timing...
  13. jamesnguyen

    Apply a logic high to a powered down processor. Will it damage it?

    Thank you all for your reply. The processor board fortunately has RC filter (470R & 22p) on all of its external interface signals. So its I/O ports are somewhat "protected" by the 470R resistor. I will need to check with the vendor to see if there resistance is enough. If not, I might need...
  14. jamesnguyen

    Apply a logic high to a powered down processor. Will it damage it?

    Thank you everyone for quick response! How do module vendors (who make GPS, Bluetooth, processor, Ethernet, etc modules) protect their modules from this condition? MikeHalloran: The processor is ADI's BF548 blackfin DSP. benta: How does protection diode protect the processor? I thought...
  15. jamesnguyen

    Apply a logic high to a powered down processor. Will it damage it?

    Hi everyone, I have a processor board which has a power input and a SPI port at its external interface. The SPI port is connected directly to the processor. What could happen to the processor if I just connect up the SPI port and apply a logic high to it without providing power to the...
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