TOBY-L4 series - System Integration Manual
UBX-16024839 - R04
Design-in
Page 118 of 143
2.15
Design-in checklist
This section provides a design-in checklist.
2.15.1
Schematic checklist
The following are the most important points for a simple schematic check:
DC supply must provide a nominal voltage at the
VCC
pin within the operating range limits.
DC supply must be capable of supporting both the highest peak and the highest averaged current
consumption values in connected mode, as specified in the
TOBY-L4 series
Data Sheet
VCC
voltage supply should be clean, with very low ripple/noise: provide the suggested bypass capacitors,
in particular if the application device integrates an internal antenna.
Do not apply loads which might exceed the limit for the maximum available current from
V_INT
supply.
Check that the voltage level of any connected pin does not exceed the relative operating range.
Provide accessible test points directly connected to the following pins of the TOBY-L4 series modules:
V_INT
,
PWR_ON
and
RESET_N
for diagnostic purposes.
Capacitance and series resistance must be limited on each SIM signal to match the SIM specifications.
Insert the suggested pF capacitors on each SIM signal and low capacitance ESD protections if accessible.
Check UART signals direction, as the modules’ signal names follow the
ITU-T V.24 Recommendation
Provide accessible test points directly connected to all the UART pins of the TOBY-L4 series modules
(
TXD
,
RXD
) for diagnostic purposes.
Provide accessible test points directly connected to all the UART3 pins of the TOBY-L4 series modules
(
TXD3
,
RXD3
) for Linux console access.
Capacitance and series resistance must be limited on each high speed line of the USB interface.
Provide accessible test points directly connected to the USB 2.0 interface pins of the TOBY-L4 series
modules (
VUSB_DET
,
USB_D+
and
USB_D–
) for diagnostic and FW update purposes.
Consider providing appropriate low value series damping resistors on SDIO lines to avoid reflections.
Add a suitable pull-up resistor (e.g. 4.7 k
) to
V_INT
or another suitable 1.8 V supply on each DDC (I
2
C)
interface line, if the interface is used.
Check the digital audio interface specifications to connect a suitable external audio device.
Capacitance and series resistance must be limited on master clock output line and each I
2
S interface line
Consider passive filtering parts on each used analog audio line.
Use transistors with at least an integrated resistor in the base pin or otherwise put a 10 k
resistor on
the board in series to the GPIO when those are used to drive LEDs.
Provide suitable precautions for EMC / ESD immunity as required on the application board.
Do not apply voltage to any generic digital interface pin of TOBY-L4 series modules before the switch-on
of the generic digital interface supply source (
V_INT
).
All unused pins can be left unconnected except the
RSVD
pin number
6
of TOBY-L4 series modules,
which must be connected to GND.
