About the module Power
ConnectCore for i.MX51 Hardware Reference Manual
42
There are three types of components that can be connected to this pin: Lithium coin cells (Primary
cell: non-rechargeable), Lithium coin cells (Secondary cell: rechargeable), and Supercaps. When a
Primary Lithium coin cell is connected, the charger must be turned off and this pin is used strictly as
an input. It is hazardous to attempt to charge Primary Lithium cells as they may vent or explode.
Secondary Lithium coin cells are only made available directly to manufacturers of equipment that
could use them, in that case they are normally required to design their product to prevent the user
gaining access to this part since there is a danger to the user if by replacing it, they fit a primary type
(the only sort that they are likely to be able to source) into the charging circuit. When a Secondary
Lithium coin cell is used, the charge termination voltage is programmable. When a Supercap is used,
the charge termination voltage should be set to the maximum value.
The advantage of using a Primary Lithium coin cell is that the energy density usually allows years of
service since the self discharge rate is low. The advantage of using a Secondary Lithium coin cell is
that the self discharge rate is usually sufficient to allow a few months of support for the RTC before it
will need recharging. The advantage of the Supercap is that it is intrinsically safe and can out-last the
Primary Lithium coin cell option, however the self discharge rate is high meaning that a 1F capacitor
at +25° C is likely to support the RTC for approximately 5 to 10 days.
The minimum voltage of the coin cell supply is +2.5V. The maximum voltage of the coin cell supply is
+3.6V.
Supply outputs
The ConnectCore for i.MX51 module provides the following supply outputs:
n +3.3 V
n +2.775 V
n SWBT (+5 V)
n +1.8 V
n +3.15 V
+3.3 V
The ConnectCore for i.MX51 module has a DC/DC converter to generate a +3.3V supply. This supply is
used on the module to power the WLAN interface, the Ethernet PHY and the Ethernet Controller.
This power regulator can be enabled/disabled by the software to save power when the module is in
the low power modes. The maximum current provided by this regulator is 1.2A.
The current available to supply off-module components is 400mA for the wireless variants of the
ConnectCore for i.MX51, and 800mA for the wired variant of the ConnectCore for i.MX51.
+2.775 V
This supply is used on the module to power the i.MX51 peripherals, the accelerometer and the i.MX51
image processing unit. The maximum current provided by this supply is 100mA.
The current available to supply off-module components is 50mA.
SWBT (+5 V)
The voltage level of the SWBT supply is +5V. The maximum current provided by this supply is 300mA.
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