SIM225 Technical Reference Manual
27
© Serious Integrated, Inc.
SIM225_TRM_A1ENUS
Revision A1
POWER SUPPLIES
There are up to three possible sources of system power for the SIM225, depending on the specific variant:
Power Signal
Description
Connectors Where Present
+5V_EXT
External Main Power
•
Power and Communications
Connector
•
Baseboard Connector
•
FFC Expansion Connector
•
PCB Edge Connector
•
LiPo Battery/Switch Connector
+5V_USBF
USB Device Power
•
USB Mini-B Device Connector
•
PCB Edge Connector
•
Tag-Connect Programming Port
•
Baseboard Connector
+VBAT_4V2
Lithium Polymer Battery (+)
Charging/Power Terminal
•
LiPo Battery/Switch Connector
•
Baseboard Connector
On all variants, both the +
5V_EXT
and
+5V_USBF
can be supplied simultaneously. On variants with LiPo
support, all three signals can be supplied simultaneously.
While all power signals can be supplied simultaneously to the SIM, each signal can only be
driven from a single source.
Connecting more than one power source to the same signal
simultaneously may damage your SIM or even connected equipment.
+5V_MAIN ON LIPO VARIANTS
On SIM225 variants with Lithium Polymer Battery support, the Texas Instruments
BQ24030 Dual Input Li-
Ion Charger with Dynamic Power Path
automatically delivers 3.6-5VDC to the
+5V_MAIN
main system
power line from one or more of the following supplies, in this order:
+5V_EXT
,
+5V_USBF
,
VBAT_4V2
.
The actual usable voltage on the
+5V_MAIN
signal will range from 3.08 (the SIM205 reset voltage) to 5.0V.
When powered by
+5V_USBF
or
+5V_EXT
it will be at or near +5V, and when powered by the LiPo
battery supply (
BAT_+4V2
) the
+5V_MAIN
signal will reflect the current battery voltage (between 3.08
and 4.2V typically).
When operated with the optional Lithium-Ion Polymer (LiPo) battery, the SIM225 may be able to operate
for several hours untethered – useful for brownout/blackout avoidance or hand-held operation. The
charge rate of the battery is limited to 950mA when charging from the external supply and 500mA when
charging from the USB device port.
The SIM225 can be powered exclusively through the
USB Device (“Function”) Power
which comes into the
module through the
USB Mini-B Device Connector
and other connectors. This is very handy for
debugging and for demos and many readily-available cell-phone USB mini-B chargers can be used. As
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