User's Manual

SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R18 Advance Information Design-in
Page 94 of 206
Figure 41 and the components listed in Table 24 show an example of a low cost power supply circuit, where the
VCC module supply is provided by a step-down switching regulator capable of delivering to VCC pins the
specified maximum peak / pulse current, transforming a 12 V supply input.
SARA-G3 / SARA-U2
12V
R5
C6C1
VCC
INH
FSW
SYNC
OUT
GND
2
6
3
1
7
8
C3
C2
D1
R1
R2
L1
U1
GND
FB
COMP
5
4
R3
C4
R4
C5
52
VCC
53
VCC
51
VCC
Figure 41: Suggested low cost solution for the VCC voltage supply application circuit using step-down regulator
Reference Description Part Number - Manufacturer
C1
22 μF Capacitor Ceramic X5R 1210 10% 25 V
GRM32ER61E226KE15 – Murata
C2
100 μF Capacitor Tantalum B_SIZE 20% 6.3V 15m:
T520B107M006ATE015 – Kemet
C3
5.6 nF Capacitor Ceramic X7R 0402 10% 50 V
GRM155R71H562KA88 – Murata
C4
6.8 nF Capacitor Ceramic X7R 0402 10% 50 V
GRM155R71H682KA88 – Murata
C5
56 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H560JA01 – Murata
C6
220 nF Capacitor Ceramic X7R 0603 10% 25 V
GRM188R71E224KA88 – Murata
D1
Schottky Diode 25V 2 A
STPS2L25 – STMicroelectronics
L1
5.2 μH Inductor 30% 5.28A 22 m:
MSS1038-522NL – Coilcraft
R1
4.7 k: Resistor 0402 1% 0.063 W
RC0402FR-074K7L – Yageo
R2
910 : Resistor 0402 1% 0.063 W
RC0402FR-07910RL – Yageo
R3
82 : Resistor 0402 5% 0.063 W
RC0402JR-0782RL – Yageo
R4
8.2 k: Resistor 0402 5% 0.063 W
RC0402JR-078K2L – Yageo
R5
39 k: Resistor 0402 5% 0.063 W
RC0402JR-0739KL – Yageo
U1
Step-Down Regulator 8-VFQFPN 3 A 1 MHz
L5987TR – ST Microelectronics
Table 24: Suggested components for low cost solution VCC voltage supply application circuit using a step-down regulator
2.2.1.3 Guidelines for VCC supply circuit design using a Low Drop-Out (LDO) linear regulator
The use of a linear regulator is suggested when the difference from the available supply rail and the VCC value is
low: linear regulators provide high efficiency when transforming a 5 V supply to a voltage value within the
module VCC normal operating range.
The characteristics of the LDO linear regulator connected to the VCC pins should meet the following
prerequisites to comply with the module VCC requirements summarized in Table 6:
x Power capabilities: the LDO linear regulator with its output circuit must be capable of providing a proper
voltage value to the VCC pins and of delivering to VCC pins the specified maximum peak / pulse current
with 1/8 duty cycle (see the SARA-G3 series Data Sheet [1] or the SARA-U2 series Data Sheet [2]).
x Power dissipation: the power handling capability of the LDO linear regulator must be checked to limit its
junction temperature to the maximum rated operating range (i.e. check the voltage drop from the max input
voltage to the min output voltage to evaluate the power dissipation of the regulator).