MIC2551_08 Datasheet, PDF (8/11 Pages) Micrel Semiconductor – USB Transceiver

MIC2551
Application Information
Power Supply Configuration
The MIC2551 can be set up for different power supply
configurations which modify the behavior of the device. Both
V_BUS and V_IF have special thresholds that detect when they
are either removed or grounded. Table 3 depicts the behavior
under the different power supply configuration scenarios that
are explained below.
Normal Mode
V_BUS is connected to the 5.0V USB bus voltage and V_IF is
connected to a supply voltage in the range of 1.6V to 3.6V. In
this case V_TRM supplies a 3.3V voltage for powering the
speed select resistor via V_PU depending on the state of the
CON pin.
Disconnect Mode
V_IF is connected to a supply in a range of 1.6V to 3.6V and
V_BUS is open or grounded. If V_BUS is opened while transmit-
ting, the data lines (D+, D–) have sharing capability and may
be driven with external devices up to approximately 3.6V if,
and only if, SUSPEND is enabled (SUS = 1). With V_BUS
ground, D+, D– sharing mode is not permitted.
Disable Mode
V_BUS is connected to the 5.0V USB bus voltage and V_IF is
open. All logic controlled inputs become high impedances,
thus minimal current will be supplied by V_IF if the input pins are
pulled up to an external source.
Alternate Power Supply Configuration Options
I/O Interface Using 3.3V
In systems where the I/O interface utilizes a 3.3V USB
controller, an alternate solution is shown in Figure 7. No extra
components are required; however, the load on V_TRM must
not exceed 10mA.
3.3V
MIC2551
V_DD
VIF
VBUS
USB
Controller
I/O
V_P/V_M/
VTRM
RCV/OE#
VBUS
Micrel, Inc.
Signal Amplitude Respective to V_IF
When operating the MIC2551, it is necessary to provide input
signals which do not exceed V_IF + 0.3V.
External ESD Protection
The use of ESD transient protection devices is not required
for operation, but is recommended. We recommend the
following devices or the equivalent:
Cooper Electronic Technologies (www.cooperet.com)
41206ESDA SurgX^
0805ESDA SurgX^
Littelfuse (www.littelfuse.com)
V0402MHS05
SP0503BAHT
Non-Multiplexed Bus
In order to save pin count for the USB logic controller
interface, the MIC2551 was designed with V_P and V_M as bi-
directional pins. To interface the MIC2551 with a non-multi-
plexed data bus, resistors can be used for low cost isolation
as shown in Figure 8.
USB Logic
Controller
(SIE)
MIC2551
V_P
V_P
10k
V_PO
V_M
V_M
10k
V_MO
Figure 8. MIC2551 Interface to
Non-Multiplexed Data Bus
Figure 7. I/O Interface Uses 3.3V
Configuration Mode
Normal
Disconnect
(D+/D– sharing)
Disconnect
Disable Mode
Prohibited
M9999-112008
VBUS/VTRM
VIF
Notes
Connected
Connected
Normal supply configuration and operation.
Open
Ground
Connected
Connected
Connected
Open
VP/VM are HIGH outputs, RCV is LOW.
With OE# = 0 and SUS = 1, data lines may be driven with
external devices up to 3.6V.
With D+, D– floating, I_IF draws less than 1µA.
VP/VM are HIGH outputs, RCV is LOW.
With D+, D– floating, I_IF draws less than 1µA.
Logic controlled inputs pins are Hi-Z.
Connected
Ground
Prohibited condition.
Table 3. Power Supply Configuration
8
November 2008