USB2512 Datasheet, PDF (15/57 Pages) SMSC Corporation – USB 2.0 High-Speed 2-Port Hub Controller

USB251xB/xBi
3.3.1.1 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 3-4. Use
Strap High to set the strap option to 1 and Stap 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).
FIGURE 3-4:
NON-REMOVABLE PIN STRAP EXAMPLE
I/O Strap Pin
HUB
+V
R k
Strap High I/O Strap Pin
HUB
Strap Low
R k
GND
3.3.1.2 Internal Pull-Down (IPD)
If a strap pin’s buffer type is IPD (pins BC_EN[x:1]), one of the two hardware configurations outlined below must be
implemented. Use the Strap High configuration to set the strap option value to 1 and Strap Low to set the strap option
value to 0.
FIGURE 3-5:
PIN STRAP OPTION WITH IPD PIN EXAMPLE
IPD Strap Pin
HUB
VSS
+V
R k
Strap High IPD Strap Pin
HUB
VSS
Strap Low
3.3.1.3 LED
If a strap pin’s buffer type is I/O and shares functionality with an LED, the hardware configuration outlined below must
be implemented. The internal logic will drive the LED appropriately (active high or low) depending on the sampled strap
option. Use the Strap High configuration to set the strap option value to 1 and Strap Low to set the strap option to 0.
FIGURE 3-6:
LED PIN STRAP EXAMPLE
Strap Pin
HUB
+V
R
LED/
k
Strap High
Strap Pin
R
HUB
k
LED/
Strap Low
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DS00001692C-page 15