User Manual
TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R08 Early Production Information Design-in
Page 74 of 158
2.2.1.3 Guidelines for VCC or 3.3Vaux 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 and the VCC or the
3.3Vaux value is low. The linear regulators provide high efficiency when transforming a 5 VDC supply to a
voltage value within the module VCC or 3.3Vaux normal operating range.
The characteristics of the Low Drop-Out (LDO) linear regulator connected to VCC or 3.3Vaux pins should meet
the following prerequisites to comply with the module VCC or 3.3Vaux 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 or 3.3Vaux pins within the specified operating range and must be capable of delivering to
VCC or 3.3Vaux pins the maximum peak / pulse current consumption during Tx burst at maximum Tx
power specified in TOBY-L2 series Data Sheet [1] or in MPCI-L2 series Data Sheet [2].
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 34 and the components listed in Table 16 show an example of a power supply circuit, where the VCC or
3.3Vaux 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 or 3.3Vaux normal operating range (e.g. ~4.1 V for the VCC and ~3.44 V
for the 3.3Vaux as in the circuits described in Figure 34 and Table 16). 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
C2R2
R3
U1
SHDN
TOBY-L2 series
71
VCC
72
VCC
70
VCC
GND
C3
5V
C1 R1
IN OUT
ADJ
GND
1
2
4
5
3
C2R4
R5
U1
SHDN
MPCI-L2 series
GND
C3
24
3.3Vaux
39
3.3Vaux
2
3.3Vaux
41
3.3Vaux
52
3.3Vaux
Figure 34: Suggested schematic design for the VCC and 3.3Vaux 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
R4
3.3 k Resistor 0402 5% 0.1 W
RC0402JR-073K3L - Yageo Phycomp
R5
1.8 k Resistor 0402 5% 0.1 W
RC0402JR-071K8L - Yageo Phycomp
U1
LDO Linear Regulator ADJ 3.0 A
LT1764AEQ#PBF - Linear Technology
Table 16: Suggested components for VCC and 3.3Vaux supply application circuit using an LDO linear regulator