USB2422 Datasheet, PDF (14/51 Pages) SMSC Corporation – 2-Port USB 2.0 Hi-Speed Hub Controller

2-Port USB 2.0 Hi-Speed Hub Controller
Datasheet
2.4
Buffer Type Descriptions
Table 2.3 Buffer Type Descriptions
BUFFER
I/O
IPD
IPU
IS
I/O12
ICLKx
OCLKx
I-R
I/O-U
DESCRIPTION
Input/Output
Input with internal weak pull-down resistor
Input with internal weak pull-up resistor
Input with Schmitt trigger
Input/Output buffer with 12 mA sink and 12 mA source
XTAL clock input
XTAL clock output
RBIAS
Analog Input/Output defined in USB specification
2.5
Strap Pin Configuration
If a pin's strap function is enabled through hub configuration selection (Table 4.1), the strap pins must
be pulled either high or low using the values provided in Table 2.4. Each strap option is dependent on
the pin’s buffer type, as outlined in the sections that follow.
Table 2.4 Strap Option Summary
STRAP OPTION
Non-Removable
Internal Pull-Down
(IPD)
LED
RESISTOR VALUE BUFFER TYPE
NOTES
47 - 100 kΩ
10 kΩ
47 - 100 kΩ
I/O
IPD
 Only applicable to port power pins
 Contains a built-in resistor
I/O
2.5.1
Non-Removable
If a strap pin’s buffer type is I/O, an external pull-up or pull-down must be implemented as shown in
Figure 2.2. Use Strap High to set the strap option to 1 and Strap Low to set the strap option to 0. When
implementing the Strap Low option, no additional components are needed (i.e., the internal pull-down
provides the resistor)
+V
R kΩ
I/O Strap Pin
HUB
Strap High
I/O Strap Pin
HUB
Strap Low
R kΩ
GND
Revision 1.0 (06-04-13)
Figure 2.2 Non-Removable Pin Strap Example
14
DATASHEET
SMSC USB2422