MIC2555 Micrel Semiconductor, MIC2555 Datasheet - Page 17

• Manufacturer Part Number: MIC2555
• Description: USB - OTG Transceiver
• Manufacturer: Micrel Semiconductor

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Pin Descriptions
VBAT
This pin is an input, and supplies power to the
transceiver. Transceiver typical operational voltages are
between 3.0 V ≤ V
VDD_LGC
This input is used to set the logic thresholds of the
following logic signals:
•
•
•
•
•
•
•
•
Important Note:
V
but never higher than V
internal pad protection diodes and current will flow from
V
allow V
This condition may damage the MIC2555, and could put
a severe load on V
MIC2555 and all other circuits attached to the V
VBUS
This pin functions as both an input to, and output from,
the transceiver. Unlike standard USB transceivers,
however, the MIC2555 always derives its operating
power from V
supply power to V
when petitioning another OTG, capable device to
become the host. To do so the vbus_chrg bit is asserted.
To power V
asserted. The difference between these two controls is
vbus_chg applies V
vbus_driv uses the 5V charge pump output. While V
is sufficient for signaling purposes, it does not meet the
4.4V minimum for V
VTRM
V
drivers, pull-up resistors and other circuitry internal to the
MIC2555. A small filter capacitor is required to insure the
regulator remains stable under all operating conditions.
A good quality 1µF capacitor is sufficient for this
purpose.
Micrel, Inc.
June 2005
DD_LGC
DD_LGC
TRM
DAT_VP_RX
SE0_VM_TX
RCV
OE_INT/
INT/
ADR0
RESET/
GPIO
supplies a regulated 3.3V to the D+, D- output
BAT
can be at a voltage less than or equal to V
to V
to go to zero while V
BUS
BAT
BAT
, as a host device, the vbus_drv bit is
. For this reason, systems should not
and never from V
BAT
BUS
BUS
DD_LGC
≤ 4.5V and 1.6V < V
when acting as a host device and
TRM
.
BAT
(3.3V) to V
as it attempts to power the
. Doing so will forward bias
DD_LGC
BUS
. The MIC2555 will
remains powered.
BUS,
DD_LGC
where as
BAT
< V
line.
BAT.
BAT
TRM
,
17
V
other system functions, typically 3 mA or less. However,
trying to source more current can reduce output drive on
D+, D- by stealing current from the differential driver.
ID
ID detects the arrival or departure of a peripheral device,
and differentiates between USB and non-USB devices.
To accomplish this, ID is pulled-up by a resistance of
approximately 100 kΩ connected to V
at ID monitored by a set of comparators. When no
device is present, ID is pulled high and NO DEVICE
condition is reported. When a Mini-A plug is inserted into
the system’s Mini-AB receptacle, ID is connected to
ground by the Mini-A plug, which triggers the MIC2555
to indicate a USB device is present.
Non-USB peripherals use a modified Mini-A plug or non-
standard cable assembly with a resistor connected
between ID and ground. When connected, this forms a
resistor divider such that a voltage of approximately ½
V
device is present.
Additionally, ID can be used to signal non-USB devices.
This is accomplished by grounding ID through a low
value resistor (~ 1 kΩ), dropping the ID voltage from ½
V
attached device. This switch is activated by the
id_gnd_out bit in Control Register 2.
C-, C+, C++
C-, C+ and C++ are the capacitors required for charge
pump operation. C- and C+ are the connections to the
‘flying’ capacitor, which creates the pumping effect. C++
is the reservoir capacitor that stores the 5V supplied to
V
Because the input source is a low voltage and the
charge pump’s regulator is set to limit V
capacitors need only be rated at 6 VDC, which helps
reduce physical size and cost.
GND_A, GND_D
MIC2555 uses separate ground lines within the chip to
isolate digital noise from analog signals. Ultimately,
these two grounds need to be tied together. This is best
done by having both grounds return separately to the
power source and join at the bypass capacitor.
RESET/
System reset. Returns all control register bits to their
default settings. MIC2555 is not equipped with an
internal power-on reset generator, and thus relies upon
the system for its reset at power up.
TRM
BAT
BAT
BUS
appears at MIC2555’s ID pin, indicating a non-USB
when vbus_drv is asserted.
can be used to supply small amounts of current to
to nearly zero, which can be detected by the
BAT
OUT
and the voltage
[phone]
M9999-060805
to 5V, these
MIC2555