SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R08
Objective Specification
Design-in
Page 98 of 188
2.3.2.2
Guidelines for RESET_N layout design
The reset circuit (
RESET_N
) requires careful layout due to the pin function: ensure that the voltage level is well
defined during operation and no transient noise is coupled on this line, otherwise the module might detect a
spurious reset request. It is recommended to keep the connection line to
RESET_N
as short as possible.
2.3.3
32 kHz signal (EXT32K and 32K_OUT)
The
EXT32K
and
32K_OUT
pins are not available on SARA-G340, SARA-G350 and SARA-U2 modules.
2.3.3.1
Guidelines for EXT32K and 32K_OUT circuit design
The application circuit of Figure 46 describes how the
32K_OUT
output pin of SARA-G300 / SARA-G310
modules can be connected to the
EXT32K
input pin, providing the 32 kHz signal which constitutes the Real
Time Clock (RTC) reference clock, so that the modules can enter the low power idle-mode, reaching low current
consumption figures (refer to the section 1.5.1.4 and to the
SARA-G3 series Data Sheet
[1]), and can provide the
RTC functions when the module is switched on.
24
32K_OUT
SARA-G300
SARA-G310
31
EXT32K
Figure 46: EXT32K application circuit using the 32 kHz signal provided by the 32K_OUT output
The application circuit of Figure 47 and Table 25 describe how an external oscillator can be connected to the
EXT32K
input pin of SARA-G300 / SARA-G310 modules, providing the external 32 kHz signal which constitutes
the RTC reference clock, so that the modules can enter the very low power idle-mode, reaching very low current
consumption figures (refer to the section 1.5.1.4 and to the
SARA-G3 series Data Sheet
[1]), and can provide the
RTC functions when the RTC block is switched on since the
V_BCKP
voltage is within the valid range.
2
V_BCKP
GND
SARA-G300
SARA-G310
31
EXT32K
32 kHz Oscillator
GND
CLKOUT
OE
VCC
C1
U1
Figure 47: EXT32K application circuit using an external 32 kHz oscillator
Reference
Description
Remarks
C1
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
U1
Low Power Clock Oscillator 32.768 kHz
OV-7604-C7 - Micro Crystal or SG-3040LC - EPSON TOYOCOM
Table 25: Example of components for the EXT32K application circuit
