4-Port USB 2.0 Controller
Datasheet
SMSC USB20H04
Page 11
Revision 1.63 (03-30-07)
DATASHEET
Table 4.4 - Biasing and Clock Oscillator Signals
NAME
BUFFER
TYPE
ACTIVE
LEVEL
DESCRIPTION
RBIAS I-R
N/A
External 1% bias resistor.
Requires a
12K
Ω
resistor to ground. Used for
setting HS transmit current level and on-chip termination impedance.
XTAL1/CLKIN ICLKx N/A
External crystal.
24MHz crystal or external clock input when a crystal is not
used.
Connect a 5M ohm resistor from this pin to XTAL2 when a crystal is used.
XTAL2 OCLKx
N/A
External crystal.
24MHz crystal. Not connected when using an external clock.
CLKIN_EN I
High
Clock Input Enable.
When high, an external CMOS clock drives XTAL1.
Table 4.5 - Power and Ground Signals
NAME
BUFFER
TYPE
ACTIVE
LEVEL
DESCRIPTION
VDD3.3 N/A
N/A
3.3V Digital Supply
. Powers digital pads.
VDD1.8 N/A
N/A
1.8V Digital Supply
. Powers digital core.
VSS N/A
N/A
Signal Ground
.
VDDA3.3 N/A
N/A
3.3V Analog Supply
. Powers analog I/O and 3.3V analog circuitry.
VDDA1.8 N/A
N/A
1.8V Analog Supply.
Powers 1.8V analog circuitry.
4.2
Buffer Type Descriptions
Table 4.6 – USB20H04 Buffer Type Descriptions
BUFFER DESCRIPTION
I Input
IPU
Input with weak internal pull-up resistor.
IPD
Input with weak internal pull-down resistor
IS
Input with Schmitt trigger
IO8
Input/Output with 8mA drive
IOSD12
Open drain with 12mA sink with Schmitt
trigger. Meets I2C-Bus Spec Version 2.1
O8
Output with 8mA drive
OD8
Open drain with 8mA sink
ICLKx
XTAL clock input
OCLKx
XTAL clock output
IO-U
Defined in USB specification
AO Analog
Output
I-R
3.3V Tolerant Analog Pin
