SARA-R4 series - System Integration Manual
UBX-16029218 - R06
Design-in
Page 38 of 102
2.2.1.3
Guidelines for VCC supply circuit design using a 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
SARA-R4 series Data Sheet
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 minimum output voltage to evaluate the power dissipation of the regulator).
Figure 12 and the components listed in Table 10 show an example of a power supply circuit, where the
VCC
module supply is provided by an LDO linear regulator capable of delivering the required current, with proper
power handling capability.
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 for the
VCC
, as in the circuits described
in Figure 12 and Table 10). This reduces the power on the linear regulator and improves the thermal design of
the circuit.
5V
C1
R1
IN
OUT
ADJ
GND
5
8
1
3
4
C2
R2
R3
U1
EN
SARA-R4 series
52
VCC
53
VCC
51
VCC
GND
C4
C3
C5
C6
Figure 12: Example of high reliability VCC supply application circuit using an LDO linear regulator
Reference
Description
Part Number - Manufacturer
C1
1 µF Capacitor Ceramic X5R 6.3 V
Generic manufacturer
C2
22 µF Capacitor Ceramic X5R 25 V
Generic manufacturer
C3
15 pF Capacitor Ceramic C0G 50 V
Generic manufacturer
C4
68 pF Capacitor Ceramic C0G 50 V
Generic manufacturer
C5
10 nF Capacitor Ceramic X7R 16 V
Generic manufacturer
C6
100 nF Capacitor Ceramic X7R 16 V
Generic manufacturer
R1
47 k
Resistor 0.1 W
Generic manufacturer
R2
41 k
Resistor 0.1 W
Generic manufacturer
R3
10 k
Resistor 0.1 W
Generic manufacturer
U1
LDO Linear Regulator 1.0 A
AP7361 – Diodes Incorporated
Table 10: Components for high reliability VCC supply application circuit using an LDO linear regulator
