ST7265X View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

ST7265X

Low speed USB 8-bit MCU family with up to 32 KB Flash/ROM

STMicroelectronics 

ST7265x

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 USBVDD. The on-

chip power Supply Manager generates an internal

interrupt when USBVDD reaches USBVIT+ (if the

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.

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, VDD pin is powered by

USBVDD supply. See Figure 24.

Once in USB mode, no power is drawn from the

step-up converter output.

For more details, refer to Figure 25.

Figure 24. External Power Supply Switch

Step-up converter

PMOS

(Note 2)

USB SWITCH

VDD1

VDD2

VDDA

Option bit

USBEN

(True OD, H/W crtl)

General Purpose I/O (I/O port DR, DDR)

Alternate Function (USBEN)

EDGE DETECTOR

WITH LATCH

4V min. from USB

USBVDD

USB VOLTAGE

DETECTOR

Interrupt Request

VITPF VITMF PLG PLGIE

DETEN

PCR REGISTER

S/W RESET

USBVIT+

USBVIT-

RESET

LOGIC

USBEN H/W

CONTROL

ST7

Note 1: Ground lines not shown

Note 2: Suggested device: IRLML6302 (International

rectifier) or Si230DS (Siliconix)

USBVIT+

USBVIT-

USBVDD

PLG bit

VITMF Bit

VITPF Bit

34/166

1

Share Link: