Ublox MAX-7C-0 Manual

Contents

Ublox MAX-7C-0 Manual Manual pdf 15 page image

MAX-7 / NEO-7 - Hardware Integration ManualUBX-13003704 - R09 Production Information DesignPage 15 of 523 Design3.1 Design checklistDesigning-in a u-blox 7 module is easy, especially when based on a u-blox reference design. Nonetheless, it paysto do a quick sanity check of the design. This section lists the most important items for a simple design check.The design checklist can also help to avoid an unnecessary PCB respin and achieve the best possibleperformance. Follow the design checklists when developing any u-blox 7 GNSS applications. This cansignificantly reduce development time and costs.3.1.1 Schematic checklist If required, does your schematic allow for using different module variants? See the u-blox website(www.u-blox.com) to compare the available features of u-blox 7 GNSS modules. Plan the use of a second interface (Test points on UART, DDC or USB) for firmware updates or as aservice connector.Power supply requirements GNSS positioning modules require a stable power supply. In selecting a strategy to achieve a clean andstable power supply, any resistance in the VCC supply line can negatively influence performance.Consider the following points: Wide power lines or even power planes are preferred. Avoid resistive components in the power line (e.g. narrow power lines, coils, resistors, etc.). Placing a filter or other source of resistance at VCC can create significantly longer acquisition times. For ground plane design, see section 3.3.3. Are all power supplies (VCC, VDD_USB) within the specified range? (See the data sheet: NEO-7 [1] orMAX-7 [2]) Compare the peak supply current consumption of your u-blox 7 module with the specification of thepower supply. (See the data sheet for more information.) At the module input, use low ESR capacitors that can deliver the required current/charge for switchingfrom backup mode to normal operation.Backup battery Use of valid time and the GNSS orbit data at startup will improve the GNSS performance i.e. enables hotstarts, warm starts and the AssistNow Autonomous process as well as AssistNow Offline. To make use ofthese features connect a battery to V_BCKP to continue supplying the backup domain in case of powerfailure at VCC_IO.If no backup supply voltage is available, connect the V_BCKP pin to VCC_IO (or to VCC if not avaiable).3.1.2 Layout checklistSee section 3.3. Is the GNSS module located according to the recommendation? Has the grounding concept been followed? Has the micro strip been kept as short as possible? Add a ground plane underneath the GNSS module to reduce interference. For improved shielding, add as many vias as possible around the micro strip, around the serialcommunication lines, underneath the GNSS module etc. Have appropriate EOS/ESD/EMI protection measures been included? This is especially important fordesigns including cellular modules.