Integration Manual
SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R11 Design-in Page 60 of 157
2.2.1.3 Guidelines for VCC supply circuit design using low drop-out linear regulator
The use of a linear regulator is suggested when the difference from the available supply rail source and the
VCC value is low. The linear regulators provide high efficiency when transforming a 5 VDC supply to a
voltage value within the module VCC normal operating range.
The characteristics of the Low Drop-Out (LDO) linear regulator connected to VCC pins should meet the
following prerequisites to comply with the module VCC requirements summarized in Table 6:
Power capabilities: the LDO linear regulator with its output circuit must be capable of providing a
voltage value to the VCC pins within the specified operating range and must be capable of delivering
to VCC pins the maximum current consumption occurring during a transmission at the maximum Tx
power, as specified in the SARA-R4/N4 series Data Sheet [1].
Power dissipation: the power handling capability of the LDO linear regulator must be checked to limit
its junction temperature to the rated range (i.e. check the voltage drop from the maximum input voltage
to the minimum output voltage to evaluate the power dissipation of the regulator).
Figure 19 and the components listed in Table 12 show an example of a high reliability power supply circuit
for the SARA-R412M modules supporting the 2G radio access technology. This example is also suitable for
the other SARA-R4/N4 series modules, where the VCC module supply is provided by an LDO linear regulator
capable of delivering the highest peak / pulse current specified for the 2G use-case, with an appropriate
power handling capability. The regulator described in this example supports a wide input voltage range,
and it includes internal circuitry for reverse battery protection, current limiting, thermal limiting and reverse
current protection.
It is recommended to configure the LDO linear regulator to generate a voltage supply value slightly below
the maximum limit of the module VCC normal operating range (e.g. ~4.1 V as in the circuit described in
Figure 20 and Table 13). This reduces the power on the linear regulator and improves the whole thermal
design of the supply circuit.
5V
C1
IN
OUT
ADJ
GND
1
2
4
5
3
R1
R2
U1
SHDN
SARA-R4/N4
52
VCC
53
VCC
51
VCC
GND
C2
C3 C4 C5 C6
Figure 19: Example of high reliability VCC supply circuit for SARA-R4/N4 series modules, using an LDO linear regulator
Reference
Description
Part Number - Manufacturer
C1
10 µF Capacitor Ceramic X5R 0603 20% 6.3 V
Generic manufacturer
C2
100 µF Capacitor Tantalum B_SIZE 20% 6.3V 15m
T520B107M006ATE015 – Kemet
C3
100 nF Capacitor Ceramic X7R 16 V
GRM155R71C104KA01 - Murata