TOBY-L2 and MPCI-L2 series - System Integration Manual
UBX-13004618 - R28
Design-in
Page 82 of 164
V_BCKP 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_BCKP
supply (see TOBY-L2 series Data Sheet
) as this can cause malfunctions in internal circuitry.
☞
ESD sensitivity rating of the V_BCKP pin is 1 kV (HBM as per 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.
2.2.2.2
Guidelines for V_BCKP layout design
V_BCKP supply requires careful layout: avoid injecting noise on this voltage domain as it may affect
the stability of the internal circuitry.
2.2.3
Generic digital interfaces supply output (V_INT)
☞
The generic digital interfaces supply V_INT pin is not available on MPCI-L2 series modules.
2.2.3.1
Guidelines for V_INT circuit design
TOBY-L2 series provide the V_INT digital interfaces 1.8 V supply output, which can be mainly used to:
Indicate when the module is switched on (as described in sections
Pull-up SIM detection signal (see section
Supply voltage translators to connect 1.8 V module digital interfaces to 3.0 V devices (see
Pull-up DDC (I
2
C) interface signals (see section
Enable external voltage regulators providing supply for external devices, as linear LDO regulators
providing the 3.3 V / 1.8 V supply rails for a u-blox ELLA-W1 series module (see section
Supply an external device, as an external 1.8 V audio codec (see section
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-L2 series Data Sheet
) 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-L2 series Data Sheet
: 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 (HBM, as per 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.
