LEON-G100 / LEON-G200 - System Integration Manual
GSM.G1-HW-09002-G3
Preliminary
System description
Page 38 of 125
Reset
push button
OUT
IN
LEON-G100 / LEON-G200
12.6 k
1.88 V
22
RESET_N
OUT
IN
LEON-G100 / LEON-G200
12.6 k
1.88 V
22
RESET_N
Application Processor
ESD
Ferrite Bead
Ferrite Bead
47 pF
47 pF
Figure 21: Application circuits to reset the module using a push button or using an application processor
When the module is in power-off mode or an internal reset occurs,
RESET_N
is pulled low by the module itself:
RESET_N
acts as an output pin in these cases since an internal open drain FET (illustrated in Figure 21 and in
Figure 22) pulls the line low.
The
RESET_N
pin can indicate to an external application that the module is switched on and is not in the reset
state:
RESET_N
is high in these cases and is low otherwise. To sense the
RESET_N
level (i.e. both the high level
and the low level), the external circuit has to be able to cause a small current through the series Schottky diode
integrated in the module as protection (illustrated in Figure 21 and Figure 22) by means of a very weak pull-
down. One of the following application circuits can be implemented to determine the
RESET_N
status:
RESET_N
connected to an LED that emits light when the module is powered up and not in reset state and
doesn’t emit light otherwise, through a biased inverting NPN transistor, with a series base resistor with a
resistance value greater or equal to 330 k
Ω
RESET_N
connected to an input pin of an application processor that senses a low logic level (0 V) when the
module is powered up and is not in reset state and senses a high logic level (i.e. 3.0 V) otherwise, through
an inverting and level shifting NPN transistor, with a series base resistor with a resistance value greater or
equal to 330 k
Ω
RESET_N
connected to an input pin of the application processor that senses a high logic level (1.8 V) when
the module is powered up and is not in reset state and senses a low logic level (0 V) otherwise, through a
weak pull-down resistor, with a resistance value greater or equal to 680 k
Ω
.
Figure 22 shows examples of application circuits to sense the
RESET_N
level.
