u-blox EVA-8M Series Hardware Integration Manual

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u-blox EVA-8M Series Hardware Integration Manual Manual pdf 8 page image

EVA-8M and EVA-M8 series - Hardware Integration ManualUBX-16010593 - R06 Design-in Page 8 of 47Early Production InformationLDOs generate stabilized voltages for the Core and RF domains of the chip respectively. The currentat VCC depends heavily on the current state of the system and is in general very dynamic.☞ Do not add any series resistance (< 0.2 Ω) to the VCC supply, as it will generate input voltage noisedue to the dynamic current conditions.☞ The equipment must be supplied by an external limited power source in compliance with the clause2.5 of the standard IEC 60950-1.2.1.1.2 I/O supply voltage (VCC_IO)The digital I/Os of the EVA-8M / EVA-M8 series GNSS modules can be supplied with a separate voltagefrom the host system connected to the VCC_IO pin of the module. The wide range of VCC_IO allowsseamless interfacing to standard logic voltage levels. However, in most applications VCC_IO and VCCshare the same voltage level and are tied together. VCC_IO supplies also the RTC and the backup RAM(BBR) during normal operation.The EVA-8M / EVA-M8 series GNSS modules come in two different IO voltage range flavors:1. EVA-M8Q with IO voltage from 2.7 V to 3.6 V2. EVA-M8M and EVA-8M with the wider range from 1.65 V to 3.6 V. The level should be setaccording to section 2.2.5.☞ VCC_IO must be supplied in order for the system to boot.☞ When running the firmware from the external SQI Flash most of the VCC_IO current is consumedby the SQI bus.2.1.1.3 Backup power supply (V_BCKP)In the event of a power failure at VCC_IO, the backup domain is supplied by V_BCKP.☞ If no backup supply is available, connect V_BCKP to VCC_IO.☞ Avoid high resistance on the V_BCKP line: During the switch from main supply to backup supply,a short current adjustment peak can cause high voltage drop on the pin with possiblemalfunctions.☞ If the “single crystal” feature is enabled (which derives the RTC frequency from the main clock),the V_BCKP pin also supplies the clock domain if there is a power failure at VCC_IO, meaning thatthe V_BCKP current will also be higher. Ensure that the capacity of the backup battery chosenmeets your requirements. EVA-M8Q module uses TCXO oscillator and does not support the“single crystal” feature. For more information about “single crystal” feature see section 2.4.22.1.1.4 USB interface power supplyVDD_USB supplies I/Os of the USB interface. If the USB interface is being used, the system can beeither self-powered, i.e. powered independently from the USB bus, or it can be bus-powered, i.e.powered through the USB connection. In bus-powered mode, the system supply voltages need to begenerated from the USB supply voltage VBUS.☞ If the USB interface is not used, the VDD_USB pin must be connected to GND.2.1.2 Power management configurationDepending on the application, the power supply schematic will differ. Some examples are shown in thefollowing sections:• Single supply voltage for VCC and VCC_IO, no backup supply see Appendix, Figure 13• Separate supply voltages for VCC, VCC_IO and V_BCKP see Appendix, Figure 14• Single supply voltage for VCC and VCC_IO, use of a backup supply see Appendix, Figure 16