TOBY-L1 and MPCI-L1 series - System Integration Manual
UBX-13001482 - R04
Advance Information
Design-in
Page 45 of 90
2.2.2
RTC supply output (V_BCKP)
The RTC supply
V_BCKP
pin is not accessible on MPCI-L1 series modules.
2.2.2.1
Guidelines for V_BCKP circuit design
TOBY-L1 series modules provide the
V_BCKP
2.5 V supply output, which can be mainly used to:
•
Pull-up the
PWR_ON
signal (see section 2.3.1 for more details)
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
(refer to
TOBY-L1 series Data Sheet
[1]) as this can cause malfunctions in internal circuitry.
V_BCKP
can only be used as an output: do not connect any external supply source on
V_BCKP.
ESD sensitivity rating of the
V_BCKP
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.
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
Digital I/O interfaces supply output (V_INT)
The generic digital interfaces supply V_INT pin is not accessible on MPCI-L1 series modules.
2.2.3.1
Guidelines for V_INT circuit design
TOBY-L1 series modules provide the
V_INT
digital interfaces 1.8 V supply output, which can be mainly used to:
•
Supply voltage translators to connect 1.8 V digital interfaces of the module to a 3.0 V device
•
Indicate when the module is switched on
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 (refer
to
TOBY-L1 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, 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.
