Ublox LISA-U1 Series System Integration Manual

Also see for LISA-U100: Integration manual

Contents

Ublox LISA-U1 Series System Integration Manual Manual pdf 18 page image

LISA-U1 series - System Integration Manual3G.G2-HW-10002-3 Preliminary System descriptionPage 18 of 125V_BCKP is the Real Time Clock (RTC) supply. When the VCC voltage is within the valid operating range, theinternal PMU supplies the Real Time Clock and the same supply voltage will be available to the V_BCKP pin. Ifthe VCC voltage is under the minimum operating limit (for example, during not powered mode), the Real TimeClock can be externally supplied via the V_BCKP pin (see section 1.5.4).When a 1.8 V or a 3 V SIM card type is connected, LISA-U1 series modules automatically supply the SIM card viathe VSIM pin. Activation and deactivation of the SIM interface with automatic voltage switch from 1.8 to 3 V isimplemented, in accordance to the ISO-IEC 7816-3 specifications.The same voltage domain used internally to supply the digital interfaces is also available on the V_INT pin, toallow more economical and efficient integration of the LISA-U1 series modules in the final application.The integrated Power Management Unit also provides the control state machine for system start up and systemreset control.1.5.2 Module supply (VCC)The LISA-U1 series modules must be supplied through the VCC pins by a DC power supply. Voltages must bestable: during operation, the current drawn from VCC can vary by some orders of magnitude, especially due tosurging consumption profile of the GSM system (described in the section 1.5.3). It is important that the systempower supply circuit is able to support peak power (refer to LISA-U1 series Data Sheet [1] for specification).Name Description RemarksVCC Module power supply input VCC pins are internally connected, but all the available padsmust be connected to the external supply in order tominimize the power loss due to series resistance.Clean and stable supply is required: low ripple and lowvoltage drop must be guaranteed.Voltage provided must always be above the minimum limit ofthe operating range.Consider that during a GSM call there are large current spikesin connected mode.GND Ground GND pins are internally connected but a good (lowimpedance) external ground can improve RF performance: allavailable pads must be connected to ground.Table 4: Module supply pinsVCC pins ESD sensitivity rating is 1 kV (Human Body Model according to JESD22-A114F). Higherprotection level can be required if the line is externally accessible on the application board. Higherprotection level can be achieved by mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistorarray) on the line connected to this pin.The voltage provided to the VCC pins must be within the normal operating range limits as specified in theLISA-U1 series Data Sheet [1]. Complete functionality of the module is only guaranteed within the specifiedminimum and maximum VCC voltage operating range.Ensure that the input voltage at the VCC pins never drops below the minimum limit of the operatingrange when the module is switched on. This is the case even during a GSM transmit burst, where thecurrent consumption can rise up to minimum peaks of 2.5 A in case of a mismatched antenna load.Operation above the operating range maximum limit is not recommended and extendedexposure beyond it may affect device reliability.