ST7554 データシートの表示（PDF） - STMicroelectronics

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ST7554

V.90 USB WORLD MODEM CONTROLLER

STMicroelectronics 

ST7554

PIN DESCRIPTION

1 - Power Supply (7 pins)

1.1 - Regulator Input Power Supply (VBUS)

This pin must be connected to USB VBUS (+5V).

It supplies the integrated analog USB transceiver.

It is also the positive regulator power supply input

(5V) when ST7554 is in bus-powered mode

(PSM = 1) and it is used to internally generate the

3.3V supply for the digital and analog circuitry.

1.2 - Regulated Analog VDD Supply (VREGA)

This pin is the analog power supply input (PSM = 0)

or analog 3.3V power supply output (PSM = 1).

This pin is the positive analog power supply for the

external Codec and DAA.

It is recommended to add a 1µF capacitor between

VREGA and GNDA as close as possible to the

IC pins.

1.3 - Regulated VDD Supply (VREGD)

This pin is the digital power supply input (PSM = 0)

or digital 3.3V power supply output (PSM = 1).

This pin is the positive digital power supply for the

external Codec and DAA.

It is recommended to add a 1µF capacitor between

VREGA and GNDA as close as possible to the

IC pins.

1.4 - Power Supply Mode (PSM)

This pin controls the VREGD and VREGA power

supply mode.

When PSM = 1, the application is bus-powered.

The 3.3V power supply is generated internally from

VBUS. In this case VREGD and VREGA are out-

puts which can be used to supply 3.3V to external

devices (see Figure 1).

When PSM = 0, the application is self-powered.

VBUS must be still connected to the VBUS Pin of

the USB connector in order to supply the integrated

USB transceiver. Anyway in this case VREGD and

VREGA must be fed by a 3.3V externally regulated

digital and analog power supplies (see Figure 2).

1.5 - Ground (DGND, AGND and GNDBUS)

DGND, AGND and GNDBUS are the digital, analog

and USB ground return pins respectively.

They should be connected together outside the

chip to the GND pin of the USB plug.

Figure 1 : ST7554 in Bus-Powered mode

(PSM = 1)

ST7554

from USB

to other

digital ICs

to other

analog ICs

8 PSM

5 VBUS

3 GNDBUS

4 VREGD

32 DGND

6 VREGA

7 AGND

Figure 2 : ST7554 in Self Powered mode

(PSM = 0)

ST7554

from USB

8 PSM

5 VBUS

3 GNDBUS

4 VREGD

from 3.3V

externally

regulated

supplies

32 DGND

6 VREGA

7 AGND

2 - USB Interface (D+ , D-)

These pins are the positive and negative USB

differential data lines. They shall be both connected

to the USB plug or USB protection circuit via 27Ω

series resistors for line impedance matching.

4/11

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