Micrel MIC74 User Manual

MIC74 Evaluation Board Micrel

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 ex­pander 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 configured to supply 3.3V to the MIC74 while
the other circuitry is supplied from a single external 5V supply.

JP20

JP20

+2.7 - 3.3V

Input

MIC74BSM-16

J2
VDD

/SHDN
/FS0

Fan mode

/FS1

jumpers

/FS2

JP23 - JP26

Slave address

jumpers

JP17 - JP19

Input jumpers

JP1 - JP8

JP21

+5V

Input

A0
A1
A2

I0
I1

I2
I3
I4
I5
I6
I7

JP21

J5
GND

J1
5V

User configurable 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 configured for fan speed control. An MIC29152, a high­current 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 Man­ager™ Software, see Appendix A.

Fan

supply

terminal

J3

LED0

LED7

07

JP22

12V

Output

jumpers

JP9 - JP16

& LEDs

TP1

TP2

(DATA)

(CLOCK)

TP1 TP2 TP3

TP3

(/ALERT)

MIC
29152BU
0000 X

U1

J6
GND

J4

VOUT

+

Fan

terminals

-

JP22

Ground

Ground

CON1

Host connections

MIC74 Evaluation Board Jumper and Connector Layout

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.

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 [phone] • fax + 1 [phone] • http://www.micrel.com

August 2000 1 MIC74

MIC74 Evaluation Board Micrel

IN

EN

GND

OUT

BYP

P7/FS2

P6/FS1

P3

P2

P1

P0

P5/FS0

P4/SHDN

MIC5205-3.3BM5

IN

EN

GND

OUT

FB

MIC29152BU

VDD

CLK

DATA

/ALERT

A2

A1

A0

GND

R10

3.3k

R

FB

3.01k

R

MIN

1k

R

F0

3.6k

R

F1

1.8k

RF21k

R2–R9 1kΩ

C3

22µF

20V

U1 MIC74BMM

4

6

8

10

12

14

16

18

20

123

12

12

21

2

1

1

3

13

13

13

13

13

13

13

21

21

21

21

21

21

21

3

21

5

7

9

11

13

15

17

19

TP2

JP22

Molex

TP1

TP3

JP21

JP20

JP17

JP18

JP1

A0

A1

JP19

A2

IN0

JP9

OUT0

OUT1

OUT2

OUT3

OUT4

OUT5

OUT6

OUT7

JP10

JP11

JP12

LED0

R9

LED1

R8

LED2

R7

LED3

R6

LED4

R5

LED5

R4

LED6

R3

LED7

R2

JP13

JP14

JP15

JP16

/SHDN
JP23

JP2

IN1

JP3

IN2

JP4

IN3

JP5

IN4

JP6

IN5

JP7

IN6

JP8

IN7

SMB_C

+5V

SMB_D

GND

C4

2.2µF

10V

J1

+5V

J4

VOUT

J6

GND

J3

+12V

J5

GND

R16

1.8k

J2

VDD

16 12

14 11

15 10

13 9

37

26

15

84

R1

10k

C5

0.01µF

C2

0.01µF

C1

0.01µF

CON1

2

2

2

2

2

2

2

2

4

5

3

1

2

21

/FS0
JP26

21

/FS1
JP25

21

/FS2
JP24

123

123

4

3

2

1

Figure 1. Evaluation Board Schematic

MIC74 2 August 2000

MIC74 Evaluation Board Micrel

Getting Started

What’s Included

Review the packing list in Table 1 to confirm that you received
all listed items. If any of the items are missing or damaged,
contact Micrel Semiconductor. The absolute latest version of
all Micrel device datasheets may be obtained from our
website at www.micrel.com.

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Table 1. Packing List

What You Must Provide

The following items are required for use with the MIC74
Evaluation Board:

• 5V, 100mA regulated power supply

• Power supply leads or cables

• SMBus/I2C compatible serial bus host for com-

munication with the MIC74

• Cable for serial host connection

• 12V-power supply rated to deliver the required

fan current*

• 12V brushless DC fan rated at no more than 1.5A
maximum*
* Required only for fan control applications

The following additional items are useful, but not required:

• Logic probe(s)

• Voltmeter(s)

• SMBus/I2C bus analyzer

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Powering the Board

The MIC74 evaluation board supports the use of dual power
supplies in order to demonstrate and make use of the
MIC74’s voltage-tolerant I/O capability. The LED indicators
can be powered from a 5V supply while the MIC74 is powered
from a lower voltage (2.7 to 3.6V). The MIC29152 linear
regulator in the optional fan control section requires a third,
higher voltage power supply. Three options are available for
powering the digital section of the evaluation board. Note that
in all cases, the pull-up resistors on /ALERT and the serial
data line are connected to the supply voltage present at J1.

Option 1

powering the board from a single 5V power supply connected
to J1 when a shorting block is installed at location JP20. The
MIC5205 generates the lower voltage (3.3V) required by the
MIC74 and feeds its VDD input via JP20. The LED’s indicators
on the board are powered from the 5V supply connected to
J1. JP21 should be removed or the 5V supply will be fed to pin
3 of the serial bus connector, CON1. Note that the pull-up
resistors on /ALERT and the serial data line are connected to
the supply voltage present at J1. The 3.3V output of U2 will
be present at J2.

Option 2

5V power supply connected to pin 3 when a shorting block is
installed at locations JP20 and JP21. The MIC5205 gener­ates the lower voltage (3.3V) required by the MIC74 and
feeds its VDD input via JP20. The supply voltage applied at
CON1 will also be present at J1. The LED’s indicators on the
board are powered from the 5V supply connected to CON1.
The pull-up resistors on /ALERT and the serial data line are
connected to the supply voltage present at pin 3 of CON1.
The 3.3V output of U2 will be present at J2.

Option 3

power the entire evaluation board via J1 and J2. J1 and J2
should be connected together and JP20 is removed. This
isolates the MIC5205 from the circuit and ties both sections
together. The LED indicators will be powered from the same
supply as the MIC74. JP21 should be removed or the supply
voltage will be fed to pin 3 of the serial bus connector, CON1.
Note that the pull-up resistors on /ALERT and the serial data
line are connected to the supply voltage present at J1.

These options are summarized in Table 2. For each case, the
terminal used as the power supply input is highlighted in bold.

: An MIC5205-3.3BM5 linear regulator, U2, permits

: The board can be powered via CON1 by a single

: A single power supply between 2.7V and 3.6V can

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Table 2. Options for Powering the Evaluation Board

August 2000 3 MIC74

MIC74 Evaluation Board Micrel

For fan control applications, an additional power supply is
connected to J3. This is nominally a 12V supply, but may be
higher, limited only by the MIC29152’s maximum input volt­age of 26V.

Care must be taken, however, to insure that the
maximum power dissipation of the regulator is not exceeded.
If the regulator overheats, its internal thermal shutdown
circuitry will deactivate it. See MIC29152 datasheet.

Any of
the power supply arrangements listed in Table 2 may be used
in conjunction with a fan power supply at J3.

Serial Bus Host

The connector provided for the serial bus host is a Molex part
number 15-83-0064, 4-conductor shielded receptacle. The
pinout of this connector is shown below. The mating connec­tor is Molex part number 15-83-1564. See Appendix A for
more information on these connectors. The serial bus signals
are also present on dual-row header JP22 and at test points
TP1 and TP2. One or more of these connection points can be
used in lieu of the specialized connector. The various serial
bus connection points are summarized in Table 3 below.

FRONT

CLK +5V DATA GND

4321

Molex 15-83-0064

There are eight possible slave addressess. Table 4 shows
each of the jumper settings and resulting slave addresses.

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DNGDNGV50010 100
DNGV5DNG0010 010

DNGV5V50010 110
V5DNGDNG0010 001
V5DNGV50010 101
V5V5DNG0010 011
V5V5V50010 111

b

b

b

b

b

b

b

b

02

h

12

h

22

h

32

h

42

h

52

h

62

h

72

h

Table 4. Selecting the MIC74 Slave Address

Pull-up Resistors

The MIC74 evaluation board includes a pull-up resistor on the
serial data line and the MIC74’s /ALERT output, resistors R16
and R1, respectively. The serial clock line also requires a pull­up resistor or current source somewhere in the system. If the
host does not have a provision for this pull-up, a pull-up
resistor will have to be added somewhere on the board, such
as between TP2 and J1. Guidelines for sizing this pull-up
resistor can be found in the SMBus specification.

in Appendix A.

See source

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Table 3. Serial Bus Connection Points

Personal computer based host adapters, cables, bus analyz­ers and other useful items can be obtained from the sources
listed in

Appendix A

.

Slave Address Selection

Before communication between the serial bus host and the
MIC74 can take place, the MIC74’s slave address must be
established. Jumpers JP17-19, marked “A0”, “A1”, and “A2”
on the PCB establish the slave address by connecting the A0,
A1, and A2 pins to 5V or ground. The address of the MIC74
is only registered at power-on and cannot be changed during
operation. To change the MIC74’s slave address, power
must be removed and then reapplied once the new settings
of JP17-19 have been established. The factory setting for the
MIC74’s slave address is 010 0000b (JP17 = JP18 = JP19 =
GND).

Checkout

Proper operation of all of the MIC74’s various functions can
be demonstrated and tested by a series of short exercises.
Each I/O pin is tested in its output mode and its input mode,
including the generation of interrupts. Lastly, the MIC74’s fan
mode operation is verified. If fan mode operation is not
desired, this section can be skipped.

Input Mode

The following steps will configure all I/O pins as inputs and
verify that the MIC74 is detecting and passing valid data.

1. Verify that jumpers JP1 - JP8 are adjusted so
that all MIC74 inputs will be grounded.

Figure 2.

2. Verify that the address selection jumpers are set
to match the slave address that will be used by
the host to communicate with the MIC74.

3. Apply power to the MIC74 evaluation board.
The MIC74 will be initialized to its default state,
all I/Os will be configured as inputs.

4. Read the data register, DATA. The value
returned should be 00h = 0000 0000b.

5. Connect any one of the input pins to 5V by
moving one of jumpers JP1-JP8. For example,
move JP3 to connect input I3 to 5V (logic high).

6. Read the data register, DATA. The value
returned should be 08h = 0000 1000b.

See

MIC74 4 August 2000