Integration Manual

Table Of Contents
TOBY-L3 series - System Integration Manual
TSD-19090601 - R13 System Integration Manual Page 122 of 143
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-L3 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
[6].
Provide accessible test points directly connected to all the UART pins of the TOBY-L3 series modules
(TXD, RXD) for diagnostic purposes.
Provide accessible test points directly connected to all the UART3 pins of the TOBY-L3 series
modules (TXD3, RXD3) for Linux debug 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-L3 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
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-L3 series modules before the
switch-on of the generic digital interface supply source (V_INT).
All unused pins of TOBY-L3 series modules can be left unconnected, which must all be connected
to GND.
2.15.2 Layout checklist
The following are the most important points for a simple layout check: