Datasheet

Power-Supply Configurations
TUSB2551A
SCES790 – JUNE 2009 ...................................................................................................................................................................................................... www.ti.com
The TUSB2551A 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 V
CC(5.0)
or V
CC(5.0)
and V
reg(3.3)
are connected. For 5-V operation, V
CC(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 V
CC(5.0)
and V
reg(3.3)
are connected to a 3.3-V source (3 V to 3.6 V).
V
CC(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; V
CC(5.0)
or V
CC(5.0)
and V
reg(3.3)
are connected. In this mode, the
internal circuits of the TUSB2551A 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 V
CC(I/O)
lost.
• Sharing mode – V
CC(I/O)
is connected; V
CC(5.0)
and V
reg(3.3)
are not connected. In this mode, the D+ and D –
pins are made 3-state, and the TUSB2551A allows external signals of up to 3.6 V to share the D+ and D –
lines. The internal circuits of the TUSB2551A ensure that virtually no current (maximum 10 mA) is drawn via
the D+ and D – lines. The power consumption through V
CC(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 V
reg(3.3)
lost.
Table 1. Power-Supply Configuration Overview
CONFIGURATION
VBUS/VTRM VIF Notes
MODE
Normal Connected Connected Normal supply configuration and operation
VP/VM are HIGH outputs, RCV is LOW.
Disconnect With OE = 0 and SUSPEND = 1, data lines may be driven
Open Connected
(D+/D – sharing) with external devices up to 3.6 V.
With D+, D – floating, I
CC(I/O)
draws less than 1 µ A.
VP/VM are HIGH outputs, RCV is LOW.
Disconnect Ground Connected
With D+, D – floating, I
CC(I/O)F
draws less than 1 µ A.
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
V
CC(5.0)
/V
reg(3.3)
5-V input/3.3-V output, 3.3-V input/3.3-V input Not present
V
CC(I/O)
Not present 1.65-V to 3.6-V input
V
PU(3.3)
High impedance (off) High impedance (off)
D+, D – High impedance High impedance
VP, VM Invalid
(1)
H
RCV Invalid
(1)
L
Inputs (SPEED, SUSPEND, OE, SOFTCON) High impedance High impedance
(1) High impedance or driven LOW
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