TUSB2551 datasheet(4/18 Pages) TI

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Power-Supply Configurations

TUSB2551

ADVANCED UNIVERSAL SERIAL BUS TRANSCEIVER

SCES667 – FEBRUARY 2008

The TUSB2551 can be used with different power-supply configurations, which can be dynamically changed. An

overview is given in Table 1.

• Normal mode – Both V

CC(I/O) and VCC(5.0) or VCC(5.0) and Vreg(3.3) are connected. For 5-V operation, VCC(5.0) is

connected to a 5-V source (4 V to 5.5 V). The internal voltage regulator then produces 3.3 V for the USB

connections. For 3.3-V operation, both VCC(5.0) and Vreg(3.3) are connected to a 3.3-V source (3 V to 3.6 V).

VCC(I/O) is independently connected to a voltage source (1.65 V to 3.6 V), depending on the supply voltage of

the external circuit.

• Disable mode – V

CC(I/O) is not connected; VCC(5.0) or VCC(5.0) and Vreg(3.3) are connected. In this mode, the

internal circuits of the TUSB2551 ensure that the D+ and D– pins are in 3-state, and the power consumption

drops to the low-power (suspended) state level. Some hysteresis is built into the detection of VCC(I/O) lost.

• Sharing mode – V

CC(I/O) is connected; VCC(5.0) and Vreg(3.3) are not connected. In this mode, the D+ and D–

pins are made 3-state, and the TUSB2551 allows external signals of up to 3.6 V to share the D+ and D–

lines. The internal circuits of the TUSB2551 ensure that virtually no current (maximum 10 mA) is drawn via

the D+ and D– lines. The power consumption through VCC(I/O) drops to the low-power (suspended) state level.

Both the VP and VM pins are driven HIGH to indicate this mode. Pin RCV is made LOW. Some hysteresis is

built into the detection of Vreg(3.3) lost.

Table 1. Power-Supply Configuration Overview

Configuration Mode

VBUS/VTRM

VIF

Notes

Normal

Connected

Normal supply configuration and operation.

VP/VM are HIGH outputs, RCV is LOW.

With OE# = 0 and SUSPEND = 1, data lines may be

Disconnect

Open

Connected

driven with

(D+/D– sharing)

external devices up to 3.6 V.

With D+, D– floating, ICC(I/O) draws less than 1 µA.

VP/VM are HIGH outputs, RCV is LOW.

Disconnect

Ground

Connected

With D+, D– floating, ICC(I/O)F draws less than 1 µA.

Disable Mode

Connected

Open

Logic controlled inputs pins are Hi-Z

Prohibited

Connected

Ground

Prohibited condition

Table 2. Pin States in Disable or Sharing Mode

PINS

DISABLE-MODE STATE

SHARING-MODE STATE

VCC(5.0)/Vreg(3.3)

5-V input/3.3-V output, 3.3-V input/3.3-V input

Not present

VCC(I/O)

Not present

1.65-V to 3.6-V input

VPU(3.3)

High impedance (off)

D+, D–

High impedance

VP, VM

Invalid(1)

RCV

Invalid(1)

Inputs (SPEED, SUSPEND, OE, SOFTCON)

High impedance

(1)

High impedance or driven LOW

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