User's Manual

TOBY-R2 series - System Integration Manual
UBX-16010572 - R04 Design-in
Page 82 of 147
2.2.3 Generic digital interfaces supply output (V_INT)
2.2.3.1 Guidelines for V_INT circuit design
TOBY-R2 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 2.6.3 for more details)
 Supply a 1.8 V u-blox 6 or subsequent u-blox GNSS receiver generation (see section 2.6.3 for more details)
 Supply an external device, as an external 1.8 V audio codec (see section 2.7.1 for more details)
V_INT supply output pin provides internal short circuit protection to limit 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 maximum available current from V_INT supply (see
the TOBY-R2 series Data Sheet [1]) as this can cause malfunctions in internal circuitry.
Since the V_INT supply is generated by an internal switching step-down regulator, the V_INT voltage
ripple can range as specified in the TOBY-R2 series Data Sheet [1]: 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.
ESD sensitivity rating of the V_INT supply pin is 1 kV (Human Body Model according to JESD22-A114).
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 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.
2.2.3.2 Guidelines for V_INT layout design
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.