August 2000 1 MIC74
MIC74 Evaluation Board
SMBus™ I/O Expander and Fan Controller Evaluation Board
General Description
This evaluation board demonstrates use of the MIC74 Serial
I/O expander and fan controller. It is designed to support rapid
prototyping of circuits employing the MIC74 as an I/O ex-
pander and/or a fan speed controller. Support is included for
dual power supplies in order to demonstrate the 5V-tolerant
I/O capabilities of the MIC74. An MIC5205 150mA LDO
regulator can be congured to supply 3.3V to the MIC74 while
the other circuitry is supplied from a single external 5V supply.
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
SMBus™ is a trademark of Intel Corporation.
I2C™ is a trademark of Philips Electronics, N.V.
IPort™ and Message Manager™ are trademarks of Microcomputer Control Corporation.
User congurable jumpers allow each of the MIC74’s I/O lines
to be used as an input or output, or the high-order lines can
be congured for fan speed control. An MIC29152, a high-
current low-dropout regulator, is included to drive common
12V brushless DC fans.
A 4-pin connector is provided to interface the evaluation
board with a serial bus host such as the IPort™, an I2C™ Host
Adapter from MCC Corp. This connector is commonly used
for interoperability testing among SMBus™ or ACCESS.bus
hosts and peripherals. For more information regarding the
IPort™ I2C™ Host Adapter and the I2C™ Message Man-
ager™ Software, see Appendix A.
J5
GND
J1
5V
A0
A1
A2
I0
I1
I2
I3
I4
I5
I6
I7
JP21
J6
GND
JP22
TP1 TP2 TP3
/SHDN
/FS0
/FS1
/FS2
J2
VDD
LED0
LED7
U1
J3
12V
J4
VOUT
JP20
MIC74BSM-16
Ground Host connections
Slave address
jumpers
JP17 - JP19
Input jumpers
JP1 - JP8
+
Fan
terminals
-
Fan
supply
terminal
+5V
Input
+2.7 - 3.3V
Input
Output
jumpers
JP9 - JP16
& LEDs
07
Fan mode
jumpers
JP23 - JP26
JP20
JP21
Ground
MIC
29152BU
0000 X
TP1
(DATA)
TP2
(CLOCK)
TP3
(/ALERT)
CON1 JP22
MIC74 Evaluation Board Jumper and Connector Layout