TOBY-L4 series - System Integration Manual
UBX-16024839 - R04
Design-in
Page 67 of 143
2.2.3
Generic digital interfaces supply output (V_INT)
2.2.3.1
Guidelines for V_INT circuit design
TOBY-L4 series provide the
V_INT
generic digital interfaces 1.8 V supply output, which can be mainly used to:
Indicate when the module is switched on (as described in sections 1.6.1, 1.6.2)
Pull-up SIM detection signal (see section 2.5 for more details)
Supply voltage translators to connect 1.8 V module generic digital interfaces to 3.0 V devices (e.g. see 2.6.1)
Pull-up DDC (I
2
C) interface signals (see section 2.6.4 for more details)
Supply a 1.8 V u-blox GNSS receiver (see section 2.6.4 for more details)
Supply an external device as an external 1.8 V audio codec (see section 2.8.2 for more details)
The
V_INT
supply output pin provides internal short circuit protection to limit the start-up current and protect
the device in short circuit situations. No additional external short circuit protection is required.
Do not apply loads which might exceed the limit for the maximum available current from
V_INT
supply as
this can cause malfunctions in the internal circuitry.
Since the
V_INT
supply is generated by an internal switching step-down regulator, it is not recommended
to supply sensitive analog circuitry without adequate filtering for digital noise.
V_INT
can only be used as an output: do not connect any external supply source on
V_INT
.
The ESD sensitivity rating of the
V_INT
supply pin is 1 kV (Human Body Model according to JESD22-
A114). A higher protection level could be required if the line is externally accessible and it can be achieved
by mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) close to the accessible point.
It is recommended to monitor the
V_INT
pin to sense the end of the internal switch-off sequence of
TOBY-L4 series modules: the
VCC
supply can be removed only after
V_INT
goes low
It is recommended to provide direct access to the
V_INT
pin on the application board by means of an
accessible test point directly connected to the
V_INT
pin, for diagnostic purposes.
2.2.3.2
Guidelines for V_INT layout design
The
V_INT
supply output is generated by an integrated switching step-down converter. Because of this, it can be
a source of noise: avoid coupling with sensitive signals.