MAX3349E
Hi-Speed USB 2.0 Full-Speed Transceiver
with UART Multiplexing Mode
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11
USB Mode
The MAX3349E is in USB mode when VBUS is greater
than VTH-BUS and the bus detect output (BD) is logic-
high. In USB mode, power for the MAX3349E is derived
from VBUS, typically provided through the USB connec-
tor. An internal linear regulator generates the required
+3.3V VTRM voltage from VBUS. VTRM powers the inter-
nal USB transceiver circuitry and the D+ enumeration
resistor. Bypass VTRM to GND with a 1F ceramic
capacitor as close to the device as possible. Do not
power external circuitry from VTRM.
Disable Mode
Connect VBUS to a system power supply and leave VL
unconnected or connect to ground to enter disable
mode. In disable mode, D+ and D- are high imped-
ance, and withstand external signals up to +5.5V. OE,
SUS, and control signals are ignored.
UART Mode
Connect VL and VUART to system power supplies, and
leave VBUS unconnected or below VTH-BUS to operate
the MAX3349E in UART mode. The MAX3349E sup-
ports VUART from +2.7V to +3.3V (see Table 1).
USB Control Signals
OE
OE controls the direction of communication for USB
mode. When OE is logic-low, VP and VM operate as
logic inputs, and D+/D- are outputs. When OE is logic-
high, VP and VM operate as logic outputs, and D+/D-
are inputs. RCV is the output of the differential USB
receiver connected to D+/D-, and is not affected by the
OE logic level.
ENUM
Drive ENUM logic-high to enable the internal 1.5k
pullup resistor from D+ to VTRM. Drive ENUM logic-low
to disable the internal pullup resistor and logically dis-
connect the MAX3349E from the USB.
SUS
Operate the MAX3349E in low-power USB suspend
mode by driving SUS logic-high. In suspend mode, the
USB differential receiver is turned off and VBUS con-
sumes 38A (typ) of supply current. The single-ended
VP and VM receivers remain active to detect a SE0
state on USB bus lines D+ and D-. The USB transmitter
Table 1. Power-Supply Configuration
INPUTS
OUTPUTS
VP
VM
D+
D-
00
0
01
0
1
10
1
0
11
1
Table 2. USB Transmit Truth Table (OE = 0)
INPUTS
OUTPUTS
D+
D-
VP
VM
RCV
0000
RCV*
0101
0
1010
1
1111X
Table 3a. USB Receive Truth Table (OE = 1,
SUS = 0)
INPUTS
OUTPUTS
D+
D-
VP
VM
RCV
0000
0
0101
0
1010
0
1111
0
Table 3b. USB Receive Truth Table (OE = 1,
SUS = 1)
*
= Last State
X = Undefined
VBUS(V)
VTRM(V)
VL(V)
VUART(V)
CONFIGURATION
+4.0 to +5.5
+3.0 to +3.6 Output
+1.4 to +2.75
GND, Unconnected, or
+2.7V to +3.3V
USB Mode
+3.0 to +5.5
+2.8 to +3.6
+1.4 to +2.75
GND or Unconnected
Battery Mode
+4.0 to +5.5
+3.0 to +3.6 Output
GND or Unconnected
GND, Unconnected, or
+2.7V to +3.3V
Disable Mode
GND or Unconnected
High Impedance
+1.4 to +2.75
+2.7V to +3.3V
UART Mode