RELEASE
Revision B1
©Serious Integrated, Inc.
28
POWER SUPPLIES
POWER INPUT:
+VEXT
The SIM535 is powered by the
+VEXT
signal available on the following connectors:
16-pin Power/Communications Connector
60-Pin Board-to-Board Expansion Connector
SHIP Programming Port
There is no support for simultaneous power connectivity or dynamic power source switching. See the
DC Characteristics
for
+VEXT
limits.
Connecting more than one power source to the SIM simultaneously may damage your SIM or even connected equipment.
Only one connector should drive the
+VEXT
signal. The remaining connectors can, within the limits of the SIM, receive
power from this signal.
The external USB device supply is not routed to any power connections on the SIM, and is only used to detect an
external host present.
Since the input voltage can have a fairly wide range, as low as 3.6V and as high as 5.5V depending on the variant, there
are several switching power supplies attached to the
+VEXT
to generate the various voltages required on the SIM535:
Signal Name
Voltage
Circuits Powered
+3V3
3.3V
MCU I/O
Memory
SDRAM, e-MMC, SD card, Serial FLASH
LCD
Logic, Touch
Peripherals
USB Host, Temp Sensor, DAC/Audio
+1V25
1.25V
MCU Core
USBH_VUSB
5.0V
USB Host A Connector
USBH_AUX_5V
5.1V
Piezo Driver
/-
9.6-18V
LED Backlight Constant Current
TURNING SIM535 OFF:
PWRDWN#
All regulators on the SIM535 can be turned off via the
PWRDWN#
signal, available on the following connectors:
16-pin Power/Communications Connector
60-Pin Board-to-Board Expansion Connector
PWRDWN#
is weakly pulled high on the SIM to deliver the default powered-on behavior. Driving this signal to
GND
via logic
(or connecting it to
GND
via a simple SPST switch) puts the SIM in power down mode.
The USB host, and LCD backlight are also powered off, so when
PWRDWN#
is asserted the SIM can consume only a few mA.
+3.3V (
+3V3
) AND +1.25V (
+1V25
) REGULATION
The
+VEXT
main power rail is converted to 3.3V (signal
+3V3
) and 1.25V (signal
+1V25
) through a switching power supply
using the IDT P9122 or equivalent switching regulator. This regulator is capable of 90%+ efficiency and more than 1A
per output.
The MCU is the only circuit on the SIM that requires 1.25V; it may draw up to 285mA at 1.25V maximum according to
the
SH7269
data sheet.
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