User Manual
LARA-R2 series - System Integration Manual
UBX-16010573 - R02 Objective Specification Design-in
Page 69 of 148
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:
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 peak / pulse current consumption during Tx burst at maximum Tx power specified in LARA-R2
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 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).
Figure 28 and the components listed in Table 21 show an example of a high reliability 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
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 28
and Table 21). 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
C2R1
R2
U1
SHDN
LARA-R2 series
52
VCC
53
VCC
51
VCC
GND
Figure 28: Example of high reliability VCC 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
9.1 k Resistor 0402 5% 0.1 W
RC0402JR-079K1L - Yageo Phycomp
R2
3.9 k Resistor 0402 5% 0.1 W
RC0402JR-073K9L - Yageo Phycomp
U1
LDO Linear Regulator ADJ 3.0 A
LT1764AEQ#PBF - Linear Technology
Table 21: Components for high reliability VCC supply application circuit using an LDO linear regulator