USB2251I datasheet(13/43 Pages) MICROCHIP

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USB2250/50i/51/51i

DS00002005A-page 13

 2009 - 2015 Microchip Technology Inc.

SD Command

SD_CMD

I/O12PU

This is a bi-directional signal that connects to

the CMD signal of the SD/MMC device and has

a weak internal pull-up resistor.

SD Write

Protected

SD_WP

105

I/O12

Designates as the Secure Digital card

mechanical write detect pin.

SD Card Detect

SD_nCD

I/O12

Designates as the Secure Digital card detection

pin.

USB INTERFACE

USB Bus Data

USB+

USB-

I/O-U

These pins connect to the USB bus data

signals.

USB Transceiver

Bias

RBIAS

127

I-R

A 12.0 k

, ±1.0% resistor is attached from VSS

to this pin in order to set the transceiver's

internal bias currents.

24 MHz Crystal

Input (External

Clock Input)

XTAL1

(CLKIN)

124

ICLKx

This pin can be connected to one terminal of the

crystal or it can be connected to an external

24/48 MHz clock when a crystal is not used.

The MA[1:0] pins will be sampled while

RESET_N is asserted, and the value will be

latched upon RESET_N negation. This will

determine the clock source and value.

24 MHz Crystal

Output

XTAL2

123

OCLKx

This is the other terminal of the crystal, or it is

left open when an external clock source is used

to drive XTAL1(CLKIN). It may not be used to

drive any external circuitry other than the crystal

circuit.

MEMORY / IO INTERFACE

Memory

Data Bus

MD[7:0]

I/O12PU

These signals are used to transfer data between

the internal CPU and the external program

memory and have weak internal pull-up

resistors.

TABLE 5-1:

USB2250/50I/51/51I 128-PIN VTQFP PIN DESCRIPTIONS (CONTINUED)

Name

Symbol

128-Pin

VTQFP

Buffer

Type

Description

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