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 76 of 164
C2
GND
C3 C4
TOBY-L2 series
71
VCC
72
VCC
70
VCC
C1 C5 C6
3V8
C2
GND
C3 C4
MPCI-L2 series
C1 C5 C6
3V3
24
3.3Vaux
39
3.3Vaux
2
3.3Vaux
41
3.3Vaux
52
3.3Vaux
Figure 37: Suggested schematic for the VCC / 3.3Vaux bypass capacitors to reduce ripple / noise on supply voltage profile
Reference Description Part Number – Manufacturer
C1 68 pF Capacitor Ceramic C0G 0402 5% 50 V GRM1555C1H680JA01 – Murata
C2 15 pF Capacitor Ceramic C0G 0402 5% 50 V GRM1555C1H150JA01 – Murata
C3 8.2 pF Capacitor Ceramic C0G 0402 5% 50 V GRM1555C1H8R2DZ01 – Murata
C4 10 nF Capacitor Ceramic X7R 0402 10% 16 V GRM155R71C103KA01 – Murata
C5 100 nF Capacitor Ceramic X7R 0402 10% 16 V GRM155R71C104KA01 – Murata
C6 330
µ
F Capacitor Tantalum D_SIZE 6.3 V 45 m  T520D337M006ATE045 – KEMET
Table 19: Suggested components to reduce ripple / noise on VCC / 3.3Vaux
☞
ESD sensitivity rating of the VCC / 3.3Vaux supply pins is 1 kV (HBM according to JESD22-A114).
Higher protection level can be required if the line is externally accessible on the application board,
e.g. if accessible battery connector is directly connected to the supply pins. Higher protection level
can be achieved by mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor) close to
accessible point.
2.2.1.7 Guidelines for battery charging circuit
TOBY-L2 modules do not have an on-board charging circuit. Figure 38 provides an example of a
battery charger design, suitable for applications that are battery powered with a Li-Ion (or Li-Polymer)
cell.
In the application circuit, a rechargeable Li-Ion (or Li-Polymer) battery cell, that features proper pulse
and DC discharge current capabilities and proper DC series resistance, is directly connected to the
VCC supply input of TOBY-L2 module. Battery charging is completely managed by the
STMicroelectronics L6924U Battery Charger IC that, from a USB power source (5.0 V typ.), charges
as a linear charger the battery, in three phases:
 Pre-charge constant current (active when the battery is deeply discharged): the battery is
charged with a low current, set to 10% of the fast-charge current
 Fast-charge constant current: the battery is charged with the maximum current, configured by
the value of an external resistor to a value suitable for USB power source (~500 mA)