USB2514 datasheet(22/63 Pages) MICROCHIP

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USB 2.0 Hi-Speed Hub Controller

Datasheet

Revision 2.2 (02-17-12)

SMSC USB251xB/xBi

DATASHEET

3.3.1

Configuring the Strap Pins

If a pin's strap function is enabled thru the hub configuration selection, (Table 5.1: Initial

Interface/Configuration Options on page 26) the strap pins must be pulled either high or low using the

values provided in Table 3.4. Each strap option is dependent on the pin’s buffer type, as outlined in

the sections that follow.

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

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

Table 3.4 Strap Option Summary

STRAP OPTION

RESISTOR VALUE

BUFFER TYPE

NOTES

Non-Removable

47 - 100 k

I/O

Internal Pull-Down

10 k

IPD

Only applicable to port power pins

Contains a built-in resistor

LED

47 - 100 k

I/O

HUB

I/O Strap Pin

Strap High

I/O Strap Pin

Strap Low

GND

R k

HUB

IPD Strap Pin

Strap High

R k

VSS

IPD Strap Pin

Strap Low

VSS

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