MIC74 查看數據表（PDF） - Micrel

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MIC74

2-Wire Serial I/O Expander and Fan Controller

Micrel 

MIC74

2-Wire Serial I/O Expander

and Fan Controller

General Description

The MIC74 is a fully programmable serial-to-parallel I/O

expander compatible with the SMBus™ (system manage-

ment bus) protocol. It acts as a “slave” on the bus,

providing eight independent I/O lines.

Each I/O bit can be individually programmed as an input or

output. If programmed as an output; each I/O bit can be

programmed as an open-drain or complementary push-pull

output. If desired, the four most significant I/O bits can be

programmed to implement fan speed control. An internal

clock generator and state machine eliminate the overhead

generally associated with “bit-banging” fan speed control.

Programming the device and reading/writing the I/O bits is

accomplished using seven internal registers. All registers

can be read by the host. Output bits are capable of directly

driving high-current loads such as LEDs. A separate

interrupt output can notify the host of state changes on the

input bits without requiring the MIC74 to perform a

transaction on the serial bus or be polled by the host.

Three address selection inputs are provided, allowing up

to eight devices to share the same bus and provide a total

of 64 bits of I/O.

The MIC74 is available in an ultra-small-footprint 16-pin

QSOP. Low quiescent current, small footprint, and low

package height make the MIC74 ideal for portable and

desktop applications.

Data sheets and support documentation can be found on

Micrel’s web site at www.micrel.com.

Features

• Provides eight bits of general purpose I/O

• Built in fan speed control logic (optional)

• 2-wire SMBus™/I2C™ compatible serial interface plus

interrupt output

• 2.7V to 3.6V operating voltage range

• 5V-tolerant I/O

• Low quiescent current: 2µA (typical)

• Bit-programmable I/O options:

– input or output

– push-pull or open-drain output

– interrupt on input changes

• Outputs can directly drive LEDs (10mA IOL)

• Up to 8 devices per bus

Applications

• General purpose I/O expansion via serial bus

• Personal computer system management

• Distributed sensing and control

• Microcontroller I/O expansion

• Fan Control

Ordering Information

Part Number

Standard

Pb-Free

MIC74BQS MIC74YQS

Temperature

Range

–40° to +85°C

Package

16-Pin QSOP

Typical Application

3.0V

R9

ALERT

DATA

CLK

MIC74

VDD

P0

LED1

/ALERT P1

DATA

P2

CLK

P3

A0

P4

A1

P5

A2

P6

GND

P7 LED8

3.0V

R1

R2

R3

R4

R5

R6

R7

R8

Serial-Bus-Controlled LED Annunciator

SMBus is a trademark of Intel Corporation. I2C is a trademark of Phillips Electronics N.V.

Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com

October 2006

1

M9999-101006

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