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Recent content by MChapman

  1. MChapman

    Power supply return path question

    Looking for specifics. I would only adjust one variable at a time here. Frequency. Once a board is designed I cannot influence copper pour therefore resistance due to copper is constant through the scenarios.
  2. MChapman

    Power supply return path question

    Attached are the datasheet, schematics and two design options for a switching supply boosting 7.2v to 12v,20mA. My question is intended to be general but I wanted to include my current project as an example. The first design is intended to have a return path shorter than the return path of the...
  3. MChapman

    SIM Card Holder Question

    Good mornig, I've googled the subject and have read through a couple of patents that showed up as well as Telit's app note, 80000NT10001a, HE-910 Hardware design guide, and Telit's software user guide 1vv0300784 and am not finding the answer. I understand that the SIM presence switch is CMOS...
  4. MChapman

    Inter chip-usb (ic-usb) questions

    Thank you both fory your remarks. I'm glad to hear that designs work with 500mils tolerance. That would explain why my first USB design worked. I made a simple USB to uart using an FTDI chip. The traces were very short but not equally matched. After learning a little more about differential...
  5. MChapman

    Inter chip-usb (ic-usb) questions

    I'm glad you caught that. It's merely a typo the lenghts are actually 18mm not 18cm. Thank you for the advice on impedance matching. If you don't mind I have another question. I have heard that the length of differential traces must be exactly equal and I have heard that there are...
  6. MChapman

    Inter chip-usb (ic-usb) questions

    Good day, I have designed a couple USB 2.0 to serial devices but am only a recent graduate (as of last Saturday) and have been asked to interface with a cell module using ic-usb. I have read the ic-usb addendum to USB 2.0 but will need to make sure the device will be robust enough to last at...
  7. MChapman

    Power rail troubleshooting

    Good morning, I designed a battery powered buck-boost with a 3.3v, 1.2A output. The battery pack is a custom by Tadiran made of 4 D-Cell 19A-h lithium batteries with a single Tadiran power plus capacitor. I have tested the battery down to -40 C and even at that cold of a temp it...
  8. MChapman

    SST25VF064C Serial Flash from Microchip

    I believe the second reason is correct. I've looked through other flash chips from various companies and noticed the same package options with the center 8 pins as NC.
  9. MChapman

    SST25VF064C Serial Flash from Microchip

    I have a question that is primarily a curiosity. The SST25VF064C chip comes in 3 packages. I will be hand placing the board so, for ease and accuracy, will focus on the two SOIC packages. My question is a result of this device coming in a 8 pin and 16 pin SOIC. Half the pins in the 16 pin...
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