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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11
21 launaMs'resUdraoBnoitaulavE47CIM

31 teehSataD47CIM
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51 teehSataD25192CIM
62 selpmaSUB25192CIM
71 teehSataD5025CIM
82 selpmaS5MB3.3-5025CIM

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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DNGDNGDNG0010 000
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

MIC74 Evaluation Board Micrel

7. Repeat steps 5 through 6 for each input in turn.

8. Confirm that the correct values were returned.

The following additional steps will verify that interrupts are
operating properly:

9. Configure jumpers JP1 - JP8 so that all inputs
are low.

10. Clear any pending interrupts by reading
STATUS

11. Enable interrupts by setting the interrupt enable
bit, IE, in the configuration register.

12. Enable interrupts on all inputs by setting all bits
in the interrupt mask register.

13. Connect a logic probe or voltmeter to TP3 to
monitor the /ALERT output. /ALERT should be
in its high state.

14. Read DATA. The data returned should be
0000 0000b.

A0
A1
A2
I0

I1

I2

I3
I4
I5
I6
I7

J1
+5V

JP19

JP18

JP17

JP1

JP2

JP3

JP4

JP5

JP6

JP7

JP8

U2

C4

MIC5205

JP20

MIC74

U3

/SHDN
/FS0

/FS1
/FS2

J2
VDD

C1

O0
O1
O2
O3

O4
O5
O6

O7

15. Connect any of the input pins to 5V by moving
one of JP1 - JP8. For example, move JP4 to
connect input I3 to 5V (logic high).

16. Confirm that /ALERT goes low and remains low
indefinitely.

17. Clear the interrupt by reading STATUS. The
value returned should match the input pattern.
(For example: 08h = 0000 1000b)

18. Verify that /ALERT returns high

19. Read DATA and verify that the value returned
matches the input data. (For example: 0000
1000b)

20. Repeat steps 15 through 19 for each input in
turn.

21. Remove all power from the MIC74 evaluation
board. Wait a few seconds for C4 to discharge.

J3

LED0

LED7

12V

R9
R8
R7
R6
R5
R4
R3
R2

C2

MIC29152BU

R10

RMIN

RFB
RF2
RF1
RF0

R1

U1

J4

VOUT

C3

J5

GND

JP21

R16

Connector

Molex

JP22

TP1

TP2

TP3

1

J6

GND

71565

2

Figure 2. Input Configuration

August 2000 5 MIC74

MIC74 Evaluation Board Micrel

Output Mode

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

1. Completely remove the jumpers from JP1 to JP8
and connect them to JP9 - JP16 to configure all
I/Os to drive the LED’s. See Figure 3 below.

2. Apply power to the board. The MIC74 will be
initialized to its power-up state.

3. Verify that all the LEDs are off at this point.

4. Configure all I/Os as outputs by setting all bits in
the data direction register, i.e., write DIR with
FFh.

J1
+5V

A0
A1
A2
I0
I1
I2
I3
I4
I5

I6
I7

U2

C4

MIC5205

JP20

MIC74

U3

/SHDN
/FS0

/FS1
/FS2

J2
VDD

C1

O0
O1
O2
O3

O4
O5
O6

JP9

JP10

JP11

JP12

JP13

JP14

JP15

JP16

O7

5. Set all I/Os to their high (open-drain) state by
setting all bits in DATA, i.e., write DATA with
FFh

6. Verify that all the LEDs are off at this point.

7. Clear any bit in the data register. For example,
write DATA with F7h = 1111 0111b to clear
output #3.

8. Verify that LED #3 turns on and all other LED’s
are off.

9. Repeat steps 7 and 8 for each output bit.

10. Remove all power from the MIC74 evaluation
board. Wait a few seconds for C4 to discharge.

J3

LED0

LED7

12V

R9
R8
R7
R6
R5
R4
R3
R2

C2

MIC29152BU

R10

RMIN

RFB
RF2
RF1
RF0

R1

U1

J4

VOUT

C3

J5

GND

JP21

R16

Molex

JP22

Connector

71565

Figure 3. Output Configuration

TP1

TP2

TP3

1

J6

GND

2

MIC74 6 August 2000

MIC74 Evaluation Board Micrel

Fan Mode

The following steps will configure the board for fan speed
control and verify proper operation.

1. Remove the eight jumpers from JP1 - JP8 and
use four of the jumpers to short JP23 - JP26.
See Figure 4 below.

2. Connect the positive lead of the 12V fan to J4
(MIC29152’s output) and the negative wire of
the 12V fan to J6 (Ground).

3. Apply power to the board. The MIC74 will be
initialized to its power-up state. See the
datasheet Applications section.

4. Connect the 12V power supply to the
MIC29152’s input at J3.

5. Verify that the fan comes on at its minimum
speed. (It will remain in this state while the
MIC74 is programmed for fan mode.)

J1
+5V

A0
A1
A2

I0

I1
I2
I3
I4
I5
I6
I7

U2

C4

MIC5205

JP20

MIC74

U3

JP23

JP26

JP25

JP24

J2
VDD

C1

/SHDN
/FS0

/FS1
/FS2

O0
O1
O2
O3

O4
O5
O6

O7

6. Enable fan mode by setting the fan bit in
DEV_CFG, i.e., write DEV_CFG with 02h.

7. Select the desired speed by writing to
FAN_SPEED. (Table 3 shows the output
voltage for the seven available speeds.)

8. Verify by observation that the fan speed
changes.

9. Verify that the output voltage of the MIC29152 is
close to the value given in Table 3 (This voltage
will vary slightly due to resistor tolerances,
component accuracy, etc.)

10. Repeat steps six and seven for each possible
fan speed value.

11. Remove all power from the MIC74 evaluation
board. Wait a few seconds for C4 to discharge.

J3

LED0

LED7

12V

R9
R8
R7
R6
R5
R4
R3
R2

C2

MIC29152BU

R10

RMIN

RFB
RF2
RF1
RF0

R1

U1

J4

VOUT

C3

J5

GND

JP21

R16

Connector

Molex

JP22

TP1

TP2

TP3

1

J6

GND

71565

2

Figure 4. Fan Configuration

August 2000 7 MIC74

MIC74 Evaluation Board Micrel

Table 5 lists the fan speed and MIC29152 output voltage
produced by a given value written into FAN_SPEED. The
actual measured voltage may vary slightly from the values
shown in the table due to resistor tolerances, component
accuracy, etc. R

in the table is the equivalent feedback

EQ

DEEPS_NAF

eulaV

00000000

b

00000000

b

10000000

b

01000000

b

11000000

b

00100000

b

10100000

b

01100000

b

11100000

b

deepSnaF

R

detceleS

BF

pu-rewopk3k1neponeponepok1V69.4
ffonafk3k1neponeponepok1V0
tsewolk3k1neponepok6.3387V99.5

tsewoldn2k3k1nepok8.1nepo346V30.7

tsewoldr3k3k1nepok8.1k6.3545V60.8

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tsehgihk3k1k1k8.1k6.3353V87.11

R

NIM

Table 5. Fan Drive Voltages vs. Value in FAN_SPEED

resistance that results from the parallel combination of RF0,
RF1, RF2, R

, as applicable for each speed setting. Refer

MIN

to the Applications section of the MIC74 datasheet for a
detailed explanation of fan mode and how to select resistors
for a given application.

R

2F

R

1F

R

0F

R

QE

V

TUO

Hardware Reference

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Table 6. Terminals

MIC74 8 August 2000

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Table 7. Test Points

MIC74 Evaluation Board Micrel

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yrotcaF

gnitteS

detrohS

nepO

detrohS

nepO

detrohS

nepO

detrohS

nepO

detrohS

nepO

detrohS

nepO

detrohS

nepO

detrohS

nepO

nepO

detrohS

nepO

detrohS

nepO

detrohS

Table 8. Jumper Options

August 2000 9 MIC74

MIC74 Evaluation Board Micrel

Printed Circuit Layouts

Top-Side Silk Screen

Bottom-Side Silk Screen

Top-Side Copper

MIC74 10 August 2000

Bottom-Side Copper

MIC74 Evaluation Board Micrel

Bill of Materials

Item Part Number Manufacturer Description Qty.

C1, C2, C5 08055C103MAT2 AVX 0.01µF 50V 3
C3 TPSC226M016R0375 AVX 22µF 16V 1
C4 TAJA225M010R AVX 2.2µF 10V 1
LED0–LED7 LTC-16KE Vishay Lite-On LED 8
R1 CRCW08051002FRT1 Vishay-Dale 10k ±1%, size 0805 or 1206 1
R10 CRCW08053301FRT1 Vishay-Dale 3.3k ±1%, size 0805 or 1206 1
R

F0

RF1, R16 CRCW08051801FRT1 Vishay-Dale 1.8k ±1%, size 0805 or 1206 2
R

, RF2, R2–R9 CRCW08051001FRT1 Vishay-Dale 1k ±1%, size 0805 or 1206 10

MIN

R

FB

U1 MIC29152-BU Micrel High-Current LDO Regulator 1
U2 MIC5205-3.3BM5 Micrel 150mA Low-Noise LDO Regulator 1
U3 MIC74BMM Micrel SMBus™ I/O Expander and Fan Controller 1
CON1 15-83-0064 Molex 4-position female connector 1

CRCW08053601FRT1 Vishay-Dale 3.6k ±1%, size 0805 or 1206 1

CRCW08053011FRT1 Vishay-Dale 3.01k ±1%, size 0805 or 1206 1

August 2000 11 MIC74

MIC74 Evaluation Board Micrel

Appendix A: SMBus Resources*

PC host adapters and software, bus analyzers, cables, and
other items can be purchased from:

Micro Computer Control Corporation
PO Box 275/ 17 Model Ave
Hopewell, New Jersey 08525 USA

Telephone: [phone]
Email: [e-mail]
http://www.mcc-us.com

The 4-conductor serial bus connector is available from Molex
as part number 15-83-0064. Mating plugs for constructing
cable assemblies are also available. A list of distributors is
available on the Molex website.

Molex Incorporated
2222 Wellington Court
Lisle, IL 60532-1682

Tel: 800/78MOLEX,
630/969-4550 (Outside USA)
Fax: [phone]
Telex: 254069
E-mail: [e-mail]
http://www.molex.com

The current SMBus specification and other information re­garding SMBus may be obtained from the SMBus website

SMBus Forum (website)
http://www.smbus.org.

*Micrel does not necessarily endorse or recommend any of
the products, services, or information sources listed above.
Micrel is not affiliated in any way with any listed company,
person, or other entity. The above information is presented
without warranty of any kind.

MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA

TEL + 1 [phone] FAX + 1 [phone] WEB http://www.micrel.com

This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or

other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.

© 2000 Micrel Incorporated

MIC74 12 August 2000