Ublox TOBY-L2 series, System Integration Manual

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TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R28 Design-in Page 74 of 164
Figure 36 and the components listed in Table 18 show an example of a low cost 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 limited input voltage range and it includes internal circuitry for current and
thermal 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 36 and Table 18 ). 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
C2 R1
R2
U1
EN
TOBY-L2 series
71 VCC
72
VCC
70
VCC
GND
C3
5V
C1
IN OUT
ADJ
GND
1
2 4
5
3
C2 R3
R4
U1
EN
MPCI-L2 series
GND
C3
24
3.3Vaux
39 3.3Vaux
2
3.3Vaux
41
3.3Vaux
52
3.3Vaux
Figure 36: 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 27 k  Resistor 0402 5% 0.1 W RC0402JR-0727KL – Yageo Phycomp
R2
4.7 k  Resistor 0402 5% 0.1 W
RC0402JR-074K7L – Yageo Phycomp
R3 12 k  Resistor 0402 5% 0.1 W RC0402JR-0712KL – Yageo Phycomp
R4 2.7 k  Resistor 0402 5% 0.1 W RC0402JR-072K7L – Yageo Phycomp
U1 LDO Linear Regulator ADJ 3.0 A LP38501ATJ-ADJ/NOPB – Texas Instrument
Table 18: Suggested components for VCC voltage supply application circuit using an LDO linear regulator
2.2.1.4 Guidelines for VCC supply circuit design using a rechargeable battery
Rechargeable Li-Ion or Li-Pol batteries connected to the VCC pins should meet the following
prerequisites to comply with the module VCC requirements summarized in
Table 7 :
 Maximum pulse and DC discharge current: the rechargeable Li-Ion battery with its related output
circuit connected to the VCC pins must be capable of delivering a pulse current as the maximum
peak current consumption during Tx burst at maximum Tx power specified in TOBY-L2 series Data
Sheet
[1] and must be capable of extensively delivering a DC current as the maximum average
current consumption specified in TOBY-L2 series Data Sheet [1] . The maximum discharge current
is not always reported in battery data sheets, but the maximum DC discharge current is typically
almost equal to the battery capacity in Amp-hours divided by 1 hour.

DC series resistance: the rechargeable battery with its output circuit must be capable of avoiding
a VCC voltage drop below the operating range summarized in
Table 7 during transmit bursts.