Datasheet

 2010 - 2015 Microchip Technology Inc. DS00001692C-page 15
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).
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.
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 3-4: NON-REMOVABLE PIN STRAP EXAMPLE
FIGURE 3-5: PIN STRAP OPTION WITH IPD PIN EXAMPLE
FIGURE 3-6: LED PIN STRAP EXAMPLE
HUBHUB
I/O Strap Pin Strap High
+V
I/O Strap Pin
Strap Low
GND
R k
R k
HUBHUB
IPD Strap Pin Strap High
R k
+V
VSS
IPD Strap Pin Strap Low
VSS
HUBHUB
Strap Pin
LED/
Strap High
Strap Pin
LED/
Strap Low
R
k
R
k
+V