RELEASE
Revision B1
©Serious Integrated, Inc.
29
The 3.3V supply (
+3V3
) is far more broadly used throughout the module, powering most of the logic and peripherals. It is
also delivered to the
60-Pin Board-to-Board Expansion Connector
and the
16-pin Power/Communications Connector
, but
is only meant to supply a small amount of power to an attached system. The amount of 3.3V power available to these
connectors is limited by (a) the total capacity of the regulator and (b) the excess power available on the
+3V3
signal after
calculating the incoming available power minus that used on the SIM535. The
DC Power Characteristics
information in
this manual can assist in this calculation: the actual amount available is highly dependent on the specific features used
on the specific variant by the system designer.
USB DEVICE (“FUNCTION”) POWER:
USBF_VBUS
The
USBF_VBUS
signal is present on the following connectors:
60-Pin Board-to-Board Expansion Connector
SHIP Programming Port
USB2.0 High-Speed Device Port
The USB Micro B VBUS signal (
USBF_VBUS
) on various other connectors is directly connected to the USB Micro B power
input: simultaneous connection may damage the SIM or connected devices such as a PC or USB Hub.
The SIM535 cannot be powered from the
USBF_VBUS
signal as the maximum power required by the SIM535 exceeds the
ability of the USB specification. The
USBF_VBUS
signal is only used by logic on the SIM535 to determine if an external USB
host has connected to the device port.
USB HOST POWER:
USBH_VUSB
Some variants include a
USB2.0 High Speed Embedded Host Port
with USB A connector. This USB port can supply power
to some USB devices, such as keyboard, mice, and thumb drives. A
TI TPS2501 USB Host Power Boost Controller
or
equivalent ensures that even if
+VEXT
is below 4.75V, the USB Host A connector is still powered with 5.0V as required by
the USB embedded host standard. The circuitry also provides overcurrent shutoff and controller notification if the device
plugged into the connector draws more than 150mA.
This supply is enabled when the
FTDI FT313HQ-R USB Host Controller
’s
PSW#
pin is asserted. This signal is delivered
active-high into the boost controller’s enable pin. The boost supply is disabled during
RESET#
and remains disabled until
the FT313’s port pin is configured by software explicitly to assert
PSW#.
The circuit delivers up to 150 mA to the
USBH_VUSB
signal on the
USB2.0 High Speed Embedded Host Port
. This 150 mA
will be sufficient for some powered devices, including USB thumb drives as well as some unpowered USB devices.
However, it will not be sufficient for higher power devices such as USB powered printers and hard drives. When this
power is exceeded, the
FAULT#
line is asserted and the circuit self-current-limits.
The USB Host power supply and any connected device can be a significant power load on the system. When initially
turned on there is an inherent short term power drain as the boost controller is enabled and the
USBH_VUSB
power
is generated and stabilized. If
+VEXT
is too low, the impedance of the external power supply too high, and/or the
transient current support of the supply insufficient, then the SIM can self-reset. Observe the minimum
recommended
+VEXT
DC Maximum Ratings
carefully when the USB host feature is used.
LCD PANEL BACKLIGHT POWER:
BLEN
AND
/BL_LED-
The
LCD Panel
has an array of LEDs creating the backlight. The LCD backlight is enabled when MCU signal
PJ8/PWM2A-
BLEN
is driven high. This enable signal has a weak pull-down, so the backlight is off until the MCU pin is initialized,
including during and directly after system
RESET#
.
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
Downloaded from
