TOBY-L4 series - System Integration Manual
UBX-16024839 - R04
System description
Page 32 of 143
Figure 13 shows the module power-on sequence, describing the following phases:
The
VCC
module supply is stable at its nominal value within the normal operating range
The
PWR_ON
input pin is set low for a valid time period, representing the switch-on event.
All the generic digital pins of the modules are tri-stated until the switch-on of their supply source (
V_INT
):
any external signal connected to the generic digital pins must be tri-stated or set low at least until the
activation of the
V_INT
supply output to avoid latch-up of circuits and allow a clean boot of the module.
The
V_INT
generic digital interfaces supply output is enabled by the integrated power management unit.
The
RESET_N
line rises suddenly to the high logic level due to internal pull-up to
V_INT
.
The internal reset signal is held low by the integrated power management unit: the baseband processor core
and all the digital pins of the modules are held in reset state.
When the internal reset signal is released, any digital pin is set in the correct sequence from the reset state
to the default operational configured state. The duration of this pins’ configuration phase differs within the
generic digital interfaces and the USB interface due to host / device enumeration timings (see section 1.9.1).
The module is fully ready to operate after all interfaces are configured.
VCC
PWR_ON
V_INT
RESET_N
Internal Reset
System State
Digital Pins State
Internal Reset
→
Operational Operational
Tristate / Floating
OFF
ON
Internal Reset
0 ms
~35 ms
~3 s
Start of interface
configuration
Module interfaces
are configured
The module starts
the switch-on routine
Figure 13: TOBY-L4 series power-on sequence description
The Internal Reset signal is not available on a module pin, but the host application can monitor the
V_INT
pin to sense the start of the TOBY-L4 series module power-on sequence.
Before the switch-on of the generic digital interface supply source (
V_INT
) of the module, no voltage
driven by an external application should be applied to any generic digital interface of the module.
Before the TOBY-L4 series module is fully ready to operate, the host application processor should not send
any AT command over the AT communication interface (USB) of the module.
The duration of the TOBY-L4 series modules’ switch-on routine can vary depending on the application /
network settings and any concurrent module activities.
