Integration Manual

SARA-R4/N4 series - System Integration Manual
UBX-16029218 - R13 Design-in Page 44 of 119
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 15mΩ
T520B107M006ATE015 – Kemet
C3 100 nF Capacitor Ceramic X7R 16 V GRM155R71C104KA01 - Murata
C4 10 nF Capacitor Ceramic X7R 16 V GRM155R71C103KA01 - Murata
C5 68 pF Capacitor Ceramic C0G 0402 5% 50 V GRM1555C1E680JA01 - Murata
C6 15 pF Capacitor Ceramic C0G 0402 5% 50 V GRM1555C1E150JA01 - Murata
R1
9.1 kΩ Resistor 0402 5% 0.1 W
Generic manufacturer
R2
3.9 kΩ Resistor 0402 5% 0.1 W
Generic manufacturer
U1 LDO Linear Regulator ADJ 3.0 A LT1764AEQ#PBF - Linear Technology
Table 12: Suggested components for high reliability VCC circuit for SARA-R4/N4 series modules, using an LDO regulator
☞
☞☞
☞ See the section 2.2.1.10, and in particular Figure 27 / Table 19, for the parts recommended to be provided if the
application device integrates an internal antenna.
Figure 20 and the components listed in Table 13 show an example of a high reliability power supply circuit for SARA-
R404M, SARA-R410M and SARA-N410 modules, which do not support the 2G radio access technology, where the module