Ublox TOBY-R2 Series System Integration Manual

Also see for TOBY-R2 Series: User guide

Contents

Ublox TOBY-R2 Series System Integration Manual Manual pdf 65 page image

TOBY-R2 series - System integration manualUBX-16010572 - R10 Design-in Page 65 of 1512.2 Supply interfaces2.2.1 Module supply (VCC)2.2.1.1 General guidelines for VCC supply circuit selection and designAll the available VCC pins have to be connected to the external supply minimizing the power loss dueto series resistance.GND pins are internally connected. Application design shall connect all the available pads to solidground on the application board, since a good (low impedance) connection to external ground canminimize power loss and improve RF and thermal performance.TOBY-R2 series modules must be sourced through the VCC pins with a proper DC power supply thatshould meet the following prerequisites to comply with the modules’ VCC requirements summarizedin Table 6.The proper DC power supply can be selected according to the application requirements (see Figure 27)between the different possible supply sources types, which most common ones are the following: Switching regulator Low Drop-Out (LDO) linear regulator Rechargeable Lithium-ion (Li-Ion) or Lithium-ion polymer (Li-Pol) battery Primary (disposable) batteryMain SupplyAvailable?BatteryLi-Ion 3.7 VLinear LDORegulatorMain SupplyVoltage > 5V?Switching Step-DownRegulatorNo, portable deviceNo, less than 5 VYes, greater than 5 VYes, always availableFigure 27: VCC supply concept selectionThe switching step-down regulator is the typical choice when the available primary supply source hasa nominal voltage much higher (e.g. greater than 5 V) than the operating supply voltage of TOBY-R2series. The use of switching step-down provides the best power efficiency for the overall applicationand minimizes current drawn from the main supply source. See sections 2.2.1.2, 2.2.1.6, 2.2.1.11, 2.2.1.12for specific design-in.The use of an LDO linear regulator becomes convenient for a primary supply with a relatively lowvoltage (e.g. less or equal than 5 V). In this case the typical 90% efficiency of the switching regulatordiminishes the benefit of voltage step-down and no true advantage is gained in input current savings.On the opposite side, linear regulators are not recommended for high voltage step-down as theydissipate a considerable amount of energy in thermal power. See sections 2.2.1.3, 2.2.1.6, 2.2.1.11,2.2.1.12 for specific design-in.If TOBY-R2 series modules are deployed in a mobile unit where no permanent primary supply sourceis available, then a battery will be required to provide VCC. A standard 3-cell Li-Ion or Li-Pol batterypack directly connected to VCC is the usual choice for battery-powered devices. During charging,batteries with Ni-MH chemistry typically reach a maximum voltage that is above the maximum ratingfor VCC, and should therefore be avoided. See sections 2.2.1.4, 2.2.1.6, 2.2.1.7, 2.2.1.11, 2.2.1.12 forspecific design-in.