DS00001726B-page 11

USB2422

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).

2.5.2

INTERNAL PULL-DOWN (IPD)

If a strap pin’s buffer type is IPD, one of the two hardware configurations outlined in Figure 2-3 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.

2.5.3

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 2-2:

NON-REMOVABLE PIN STRAP EXAMPLE

FIGURE 2-3:

IPD PIN STRAP EXAMPLE

FIGURE 2-4:

LED PIN STRAP EXAMPLE

HUB

I/O Strap Pin

Strap High

+V

HUB

I/O Strap Pin

Strap Low

GND

R k

Ω

R k

Ω

HUB

HUB

IPD Strap Pin

Strap High

R k

Ω

+V

VSS

IPD Strap Pin

Strap Low

VSS

HUB

Strap Pin

LED/

Strap High

HUB

Strap Pin

LED/

Strap Low

R

k

Ω

R

k

Ω