SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R26
Design-in
Page 104 of 217
Figure 44 and the components listed in Table 27 show an example of a low cost power supply circuit, where the
VCC
module supply is provided by an LDO linear regulator capable of delivering the specified highest peak /
pulse current, with proper power handling capability. The regulator described in this example supports a limited
input voltage range and it includes internal circuitry for current and thermal 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 44
and Table 27). 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
C2
R1
R2
U1
EN
SARA-G3 / SARA-U2
52
VCC
53
VCC
51
VCC
GND
Figure 44: Suggested low cost solution for the VCC voltage supply application circuit using an LDO linear regulator
Reference
Description
Part Number - Manufacturer
C1, C2
10 µF Capacitor Ceramic X5R 0603 20% 6.3 V
GRM188R60J106ME47 - Murata
R1
27 k
Resistor 0402 5% 0.1 W
RC0402JR-0727KL - Yageo Phycomp
R2
4.7 k
Resistor 0402 5% 0.1 W
RC0402JR-074K7L - Yageo Phycomp
U1
LDO Linear Regulator ADJ 3.0 A
LP38501ATJ-ADJ/NOPB - Texas Instrument
Table 27: Suggested components for low cost solution VCC voltage supply application circuit using an LDO linear regulator
2.2.1.4
Guidelines for VCC supply circuit design using a rechargeable Li-Ion or Li-Pol battery
Rechargeable Li-Ion or Li-Pol batteries connected to the
VCC
pins should meet the following prerequisites to
comply with the module
VCC
requirements summarized in Table 6:
Maximum pulse and DC discharge current
: the rechargeable Li-Ion battery with its output circuit must be
capable of delivering to
VCC
pins the specified maximum peak / pulse current with 1/8 duty cycle, and a DC
current greater than the module maximum average current consumption (refer to the
SARA-G3
series Data
[1] or the
SARA-U2 series Data Sheet
[2]). The maximum pulse discharge current and the maximum
DC discharge current are not always reported in battery data sheets, but the maximum DC discharge current
is typically almost equal to the battery capacity in Amp-hours divided by 1 hour.
DC series resistance
: the rechargeable Li-Ion battery with its output circuit must be capable of avoiding a
VCC voltage drop greater than 400 mV during transmit bursts.
