u-blox TOBY-L4 Series System Integration Manual

Contents

TOBY-L4 series - System Integration ManualUBX-16024839 - R04 Design-inPage 57 of 1432.2.1.3 Guidelines for VCC supply circuit design using a Low Drop-Out linear regulatorThe use of a linear regulator is suggested when the difference from the available supply rail source and the VCCvalue is low. The linear regulators provide high efficiency when transforming a 5 VDC supply to a voltage valuewithin the module VCC normal operating range.The characteristics of the Low Drop-Out (LDO) linear regulator connected to the VCC pins should meet thefollowing prerequisites to comply with the module VCC requirements summarized in Table 7: Power capabilities: the LDO linear regulator with its output circuit must be capable of providing a voltagevalue to the VCC pins within the specified operating range and must be capable of delivering to the VCCpins the maximum peak / pulse current consumption during Tx burst at maximum Tx power specified in theTOBY-L4 series Data Sheet [1]. Power dissipation: the power handling capability of the LDO linear regulator must be checked to limit itsjunction temperature to the maximum rated operating range (i.e. check the voltage drop from the maximuminput voltage to the minimum output voltage to evaluate the power dissipation of the regulator).Figure 22 and the components listed in Table 15 show an example of a power supply circuit where the VCCmodule supply is provided by an LDO linear regulator capable of delivering the required current with a suitablepower handling capability.It is recommended to configure the LDO linear regulator to generate a voltage supply value slightly below themaximum limit of the module VCC normal operating range (e.g. ~4.1 V for the VCC, as in the circuits illustratedin Figure 22 and Table 15). This reduces the power on the linear regulator and improves the thermal design ofthe circuit.5VC1 R1IN OUTADJGND12 453C2R2R3U1SHDNTOBY-L4 series71 VCC72 VCC70 VCCGNDC3Figure 22: Example of high reliability VCC supply application circuit using an LDO linear regulatorReference Description Part Number - ManufacturerC1, C2 10 μF Capacitor Ceramic X5R 0603 20% 6.3 V GRM188R60J106ME47 - MurataC3 330 μF Capacitor Tantalum D_SIZE 6.3 V 45 m T520D337M006ATE045 - KEMETR1 47 k Resistor 0402 5% 0.1 W RC0402JR-0747KL - Yageo PhycompR2 9.1 k Resistor 0402 5% 0.1 W RC0402JR-079K1L - Yageo PhycompR3 3.9 k Resistor 0402 5% 0.1 W RC0402JR-073K9L - Yageo PhycompU1 LDO Linear Regulator ADJ 3.0 A LT1764AEQ#PBF - Linear TechnologyTable 15: Components for high reliability VCC supply application circuit using an LDO linear regulator