u-blox TOBY-L4 Series System Integration Manual

Contents

TOBY-L4 series - System Integration ManualUBX-16024839 - R04 Design-inPage 60 of 1432.2.1.6 Additional guidelines for VCC supply circuit designTo reduce voltage drops, use a low impedance power source. The series resistance of the power supply lines(connected to the modules’ VCC and GND pins) on the application board and battery pack should also beconsidered and minimized: cabling and routing must be as short as possible to minimize power losses.Three pins are allocated to the VCC supply. Several pins are designated for GND connection. It is recommendedto correctly connect all of them to supply the module to minimize series resistance losses.For modules supporting 2G radio access technology, to avoid voltage drop undershoot and overshoot at thestart and end of a transmit burst during a GSM call (when current consumption on the VCC supply can rise up asspecified in the TOBY-L4 series Data Sheet [1]), place a bypass capacitor with large capacitance (at least 100 μF)and low ESR near the VCC pins, for example: 330 μF capacitance, 45 m ESR (e.g. KEMET T520D337M006ATE045, Tantalum Capacitor)To reduce voltage ripple and noise, improving RF performance especially if the application device integrates aninternal antenna, place the following bypass capacitors near the VCC pins: 68 pF capacitor with Self-Resonant Frequency in the 800/900 MHz range (e.g. Murata GRM1555C1H680J) 15 pF capacitor with Self-Resonant Frequency in 1800/1900 MHz range (e.g. Murata GRM1555C1E150J) 8.2 pF capacitor with Self-Resonant Frequency in 2500/2600 MHz range (e.g. Murata GRM1555C1H8R2D) 10 nF capacitor (e.g. Murata GRM155R71C103K) to filter digital logic noise from clocks and data sources 100 nF capacitor (e.g. Murata GRM155R61C104K) to filter digital logic noise from clocks and data sourcesA suitable series ferrite bead can be correctly placed on the VCC line for additional noise filtering if required bythe specific application according to the whole application board design.C2GNDC3 C4TOBY-L4 series71VCC72VCC70VCCC1 C5 C63V8+Figure 24: Suggested schematic for the VCC bypass capacitors to reduce ripple / noise on the supply voltage profileReference Description Part Number - ManufacturerC1 8.2 pF Capacitor Ceramic C0G 0402 5% 50 V GRM1555C1H8R2DZ01 - MurataC2 15 pF Capacitor Ceramic C0G 0402 5% 50 V GRM1555C1H150JA01 - MurataC3 68 pF Capacitor Ceramic C0G 0402 5% 50 V GRM1555C1H680JA01 - MurataC4 10 nF Capacitor Ceramic X7R 0402 10% 16 V GRM155R71C103KA01 - MurataC5 100 nF Capacitor Ceramic X7R 0402 10% 16 V GRM155R71C104KA01 - MurataC6 330 μF Capacitor Tantalum D_SIZE 6.3 V 45 m T520D337M006ATE045 - KEMETTable 17: Suggested components to reduce ripple / noise on the VCCThe necessity of each part depends on the specific design, but it is recommended to provide all the bypasscapacitors illustrated in Figure 24 / Table 17 if the application device integrates an internal antenna.The ESD sensitivity rating of the VCC supply pins is 1 kV (HBM as per JESD22-A114). A higher protectionlevel can be required if the line is externally accessible on the application board, e.g. if the accessiblebattery connector is directly connected to the supply pins. A higher protection level can be achieved bymounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor) close to the accessible point.