MIC74_06 Datasheet, PDF (1/18 Pages) Micrel Semiconductor – 2-Wire Serial I/O Expander and Fan Controller

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 I_OL)
• 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 [phone] • fax + 1 [phone] • http://www.micrel.com
October 2006
1
M9999-101006