MIC2550BML Micrel Inc, MIC2550BML Datasheet - Page 8

MIC2550BML

Manufacturer Part Number
MIC2550BML
Description
Manufacturer
Micrel Inc
Datasheet

Specifications of MIC2550BML

Number Of Transceivers
1
Esd Protection
YeskV
Operating Supply Voltage (typ)
Not RequiredV
Operating Temperature Classification
Industrial
Operating Supply Voltage (max)
Not RequiredV
Operating Supply Voltage (min)
Not RequiredV
Pin Count
16
Mounting
Surface Mount
Operating Temperature (max)
85C
Operating Temperature (min)
-40C
Lead Free Status / RoHS Status
Not Compliant

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MIC2550
Applications Information
The MIC2550 is designed to provide USB connectivity in
mobile systems where system supply voltages are not avail-
able to satisfy USB requirements. The MIC2550 can operate
down to supply voltages of 2.5V and still meet USB physical
layer specifications. As shown in the system diagram, the
MIC2550 takes advantage of USB’s supply voltage, V
operate the transceiver. The system voltage, V
set the reference voltage used by the digital I/O lines (VP, VM,
RCV, OE#, SPD, and SUS pins) interfacing to the system.
Internal circuitry provides translation between the USB and
system voltage domains. V
voltage rail for the system.
In addition, a 3.3V, 10% termination supply voltage, V
provided to support speed selection. A 0.47µF (minimum)
capacitor from V
As shown in the typical application diagram, a 1µF capacitor
is recommended. A 1.5K resistor is required between this pin
and the D+ or D– lines to respectively specify full-speed or
low-speed operation.
Power Supply Configurations
V
When the V
path between V
from V
can arise in systems where V
supply that can be switched off such as in the case of a
desktop PC. Adding a Schottky diode, such as the ZHCS1000
by Zetex, in series with V
during this condition. A solution is shown in Figure 8 below.
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 9. This
configuration has the advantage over Figure 8, in that no
extra components are needed. Ensure that the load on V
does not exceed 1mA total.
M9999-031805
IF
Note: *(Optional) See Text - Power Supply Configurations
/V
BUS
3.3V
IF
Figure 8. Solution to V
Power Controller
to V
Switched
Controller
BUS
USB Device
Figure 9. I/O Interface Uses 3.3V
BUS
V
USB
DD
input pin is pulled to ground a low impedance
IF
TRM
thereby damaging the MIC2550. This issue
and V
to ground is required to ensure stability.
I/O
BUS
VIF
BUS
MIC2550
IF
VIF
V
RCV/OE#
will typically be the main supply
P
can cause a high current flow
VBUS
/V
will prevent any current flow
BUS
MIC2550
M
/
IF
/V
is driven from a power
ZHCS1000 or
BUS
VTRM
VBUS
*(Optional)
equivalent
D1
Switching
IF
, is used to
1µF min
VBUS
BUS
TRM
VBUS
TRM
, to
, is
8
Internal 3.3V Source
If the device is self-powered and has 3.3V available, the
circuit in Figure 10 is yet another power supply configuration
option. In this configuration, the internal regulator is disabled
and the 3.3V source and not V
Suspend
When the suspend pin (SUS) is high, power consumption is
reduced to a minimum. V
are still functional to enable the device to detect USB activity.
For minimal current consumption in suspend mode, it is
recommended that OE# = 1.
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 Electronics Technologies (www.cooperet.com)
Littelfuse (www.littelfuse.com)
Non-Multiplexed Bus
To save pin count for the USB logic controller interface, the
MIC2550 was designed with V
To interface the MIC2550 with a non-multiplexed data bus,
resistors can be used for low cost isolation as shown in
Figure 11.
41206ESDA SurgX
0805ESDA SurgX
V0402MHS05
SP0503BAHT
Figure 11. MIC2550 Interface to
USB Logic
Controller
Non-Multiplexed Data Bus
Figure 10. Powering Chip
from Internal 3.3V Source
(SIE)
VIF
V
®
V
V
V
MO
®
PO
MIC2550
M
P
TRM
VTRM
VBUS
is not disabled. RCV, V
10k
10k
P
BUS
and V
powers the entire chip.
V
V
P
M
MIC2550
M
as bidirectional pins.
3.3V
March 2005
Micrel, Inc.
P
and V
M

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