Integration Manual

SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R11 Design-in Page 53 of 157
2.2 Supply interfaces
2.2.1 Module supply (VCC)
2.2.1.1 General guidelines for VCC supply circuit selection and design
All the available VCC pins have to be connected to the external supply minimizing the power loss due to
series resistance.
GND pins are internally connected. Application design shall connect all the available pads to solid ground
on the application board, since a good (low impedance) connection to external ground can minimize power
loss and improve RF and thermal performance.
SARA-R4/N4 series modules must be sourced through the VCC pins with a suitable DC power supply that
should meet the following prerequisites to comply with the modules’ VCC requirements summarized in
Table 6.
The appropriate DC power supply can be selected according to the application requirements (see Figure
15) 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) battery
Main Supply
Available?
Bat t ery
Li-Ion 3.7 V
Linear LDO
Regulat or
Main Supply
Volt age > 5V?
Swit ching St ep-Down
Regulat or
No, portable device
No, less than 5 V
Yes, great er t han 5 V
Yes, always available
Figure 15: VCC supply concept selection
The switching step-down regulator is the typical choice when primary supply source has a nominal voltage
much higher (e.g. greater than 5 V) than the operating supply voltage of SARA-R4/N4 series. The use of
switching step-down provides the best power efficiency for the overall application and minimizes current
drawn from the main supply source. See section 2.2.1.2 for design-in.
The use of an LDO linear regulator becomes convenient for a primary supply with a relatively low voltage
(e.g. less or equal than 5 V). In this case, the typical 90% efficiency of the switching regulator diminishes
the benefit of voltage step-down and no true advantage is gained in input current savings. On the opposite