ST7265XEVALMS STMicroelectronics, ST7265XEVALMS Datasheet - Page 33

• Manufacturer Part Number: ST7265XEVALMS
• Manufacturer: STMicroelectronics

Specifications of ST7265XEVALMS

• Lead Free Status / Rohs Status: Supplier Unconfirmed

POWER SUPPLY MANAGEMENT (Cont’d)
6.4.2.1 Switching from Stand-Alone Mode to
USB Mode
In Stand-Alone Mode, when the user plugs in the
USB cable, 4V min. is input to USBV
chip power Supply Manager generates an internal
interrupt when USBV
PLGIE bit in the PCR register is set). The user pro-
gram then can finish the current processing, and
MUST generate a software RESET afterwards.
This puts the microcontroller into reset state and
all I/O ports go into input high impedance mode.
Figure 23. External Power Supply Switch
(Note 2)
PMOS
4V min. from USB
Note 1: Ground lines not shown
Note 2: Suggested device: STN3PF06 (STMicroelectronics)
Note 3: To allow USB cable unplug detection, output voltage of step-up converter should be low
Step-up converter
enough to not enduce (through PMOS substrate diode) voltage greater than USBV
on USBV
USB SWITCH
DD
(Note 3)
DD
pin
reaches USBV
V
(True OD, H/W ctrl)
USBV
V
V
V
DDF
USBEN
ST7
DD1
DDA
DD2
DD
DD
IT+
. The on-
(if the
USB VOLTAGE
DETECTOR
REGULATOR
USBV
USBV
Option bit
PLL
IT+
IT-
During and after this (software induced) reset
phase, the USBEN pin is set to output low level by
hardware. This causes the USB SWITCH to be
turned ON. Consequently, V
USBV
Once in USB mode, no power is drawn from the
step-up converter output.
For more details, refer to
General Purpose I/O (I/O port DR, DDR)
Alternate Function (USBEN)
VITPF
USBV
USBV
USBV
PLG bit
VITMF Bit
VITPF Bit
DD
supply. See
VITMF
IT+
IT-
DD
PLG
EDGE DETECTOR
WITH LATCH
PCR REGISTER
PLGIE
Figure
Figure
USBEN H/W
CONTROL
DD
23.
RESET
LOGIC
pin is powered by
24.
Interrupt Request
S/W RESET
DETEN
IT-
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