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TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R28
Design-in
Page 73 of 164
2.2.1.3
Guidelines for 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
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 or MPCI-L2 Data Sheet
Power dissipation: the power handling capability of the linear regulator must be checked to limit
its junction temperature to the maximum rated 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).
and the components listed in
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
). 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-L2 series
71
VCC
72
VCC
70
VCC
GND
C3
5V
C1
R1
IN
OUT
ADJ
GND
1
2
4
5
3
C2
R4
R5
U1
SHDN
MPCI-L2 series
GND
C3
24
3.3Vaux
39
3.3Vaux
2
3.3Vaux
41
3.3Vaux
52
3.3Vaux
Figure 35: 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
µ
F Capacitor Ceramic X5R 0603 20% 6.3 V
GRM188R60J106ME47 – Murata
C3
330
µ
F 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 17: Suggested components for VCC and 3.3Vaux supply application circuit using an LDO linear regulator