USB251XB datasheet(15/57 Pages) MICROCHIP

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DS00001692D-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

HUB

I/O Strap Pin

Strap High

I/O Strap Pin

Strap Low

GND

R k



R k



HUB

IPD Strap Pin

Strap High

R k



VSS

IPD Strap Pin

Strap Low

VSS

HUB

Strap Pin

LED/

Strap High

Strap Pin

LED/

Strap Low



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