American Audio UCD-200 - REV 8-10 User Manual download pdf (Page 11)

SARA-U2 series - Data Sheet

UBX-13005287 - R05 Early Production Information Interfaces

Page 11 of 51

2 Interfaces

2.1 Power management

2.1.1 Module supply (VCC)

SARA-U2 modules must be supplied through the VCC pins by a DC power supply. Voltages must be stable:

during operation, the current drawn from VCC can vary by some order of magnitude, especially due to the

surging consumption profile of the GSM system (described in SARA-G3 and SARA-U2 series System Integration

Manual [7]). It is important that the system power supply circuit is able to support peak power.

2.1.2 RTC supply (V_BCKP)

V_BCKP is the Real Time Clock (RTC) supply of SARA-U2 modules. When VCC voltage is within the valid

operating range, the internal Power Management Unit (PMU) supplies the RTC and the same supply voltage is

available on V_BCKP pin. If the VCC voltage is under the minimum operating limit (e.g. during not powered

mode), the V_BCKP pin can externally supply the RTC.

2.1.3 Generic digital interfaces supply (V_INT)

SARA-U2 modules provide a 1.8 V supply rail output on the V_INT pin, which is internally generated when the

module is switched on. The same voltage domain is used internally to supply the generic digital interfaces of the

modules. The V_INT supply output can be used in place of an external discrete regulator optimizing the bill of

material for various applications, e.g. with u-blox GNSS receivers operating at 1.8 V.

2.2 Antenna

2.2.1 Antenna RF interface (ANT)

The ANT pin has an impedance of 50  and provides the RF antenna interface of SARA-U2 modules.

2.2.2 Antenna detection (ANT_DET)

The ANT_DET pin is an Analog to Digital Converter (ADC) input to sense the antenna presence (as optional

feature), evaluating the resistance from the ANT pin to GND by means of an external antenna detection circuit

implemented on the application board (for more details see the SARA-G3 and SARA-U2 series System

Integration Manual [7] and the u-blox AT Commands Manual [4], +UANTR).

2.3 System functions

2.3.1 Module power-on

SARA-U2 modules can be switched on in one of the following ways:

 Rising edge on VCC pins to a valid voltage for module supply, i.e. applying module supply

 Low pulse on PWR_ON pin, i.e. forcing the pin (normally high with external pull-up) to a low level for a valid

time period (see section 4.2.6): PWR_ON pin requires an external pull-up resistor to set its value to logic

high and may not be left floating

 Rising edge on RESET_N pin, i.e. releasing the pin from the low level, normally high with internal pull-up

 RTC alarm, i.e. pre-programmed scheduled time by AT+CALA command

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American Audio UCD-200 - REV 8-10 User Manual Page 11