TOBY-L4 series - System Integration Manual
UBX-16024839 - R04
Design-in
Page 57 of 143
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 the
VCC
pins should meet the
following prerequisites to comply with the module
VCC
requirements summarized in Table 7:
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 the
VCC
pins the maximum peak / pulse current consumption during Tx burst at maximum Tx power specified in the
TOBY-L4 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 maximum
input voltage to the minimum output voltage to evaluate the power dissipation of the regulator).
Figure 22 and the components listed in Table 15 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 a suitable
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 illustrated
in Figure 22 and Table 15). This reduces the power on the linear regulator and improves the thermal design of
the circuit.
5V
C1
R1
IN
OUT
ADJ
GND
1
2
4
5
3
C2
R2
R3
U1
SHDN
TOBY-L4 series
71
VCC
72
VCC
70
VCC
GND
C3
Figure 22: 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
C3
330 µF Capacitor Tantalum D_SIZE 6.3 V 45 m
T520D337M006ATE045 - KEMET
R1
47 k
Resistor 0402 5% 0.1 W
RC0402JR-0747KL - Yageo Phycomp
R2
9.1 k
Resistor 0402 5% 0.1 W
RC0402JR-079K1L - Yageo Phycomp
R3
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 15: Components for high reliability VCC supply application circuit using an LDO linear regulator