MAX1668 Evaluation System

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3

Simple SMBus Commands

There are two methods for communicating with the

MAX1668: through the normal user-interface panel or

through the SMBus commands available from pressing

the MAXSMBUS button. A display will pop up that

allows the SMBus protocols, such as Read Byte and

Write Byte, to be executed. To stop normal user-inter-

face execution so that it does not override the manually

set values, turn off the update timer by unchecking the

Automatic Read checkbox.

The SMBus dialog boxes accept numeric data in bina-

ry, decimal, or hexadecimal. Hexadecimal numbers

should be prefixed by $ or 0x. Binary numbers must be

exactly 8 digits.

Note: In places where the slave address asks for an 8-bit value,

it must be the 7-bit MAX1668 slave address as determined by

ADD0 and ADD1 with the last bit (read/write bit) always set to

zero (Table 1).

Data Logging

Check the Data Logging checkbox to activate data

logging. Data logging saves temperature and status

data to a text file that includes a time/date stamp next

to each data point. If Automatic Read is enabled, data

is sampled at 4Hz; however, the data is logged to the

file only if either the temperature or status change. This

slows the growth of the data-logging file. When

Automatic Read is disabled, the data is logged each

time the Read All button is clicked. To stop data log-

ging, uncheck the Data Logging checkbox.

Detailed Hardware Description

Jumper and Switch Settings

Two jumpers set the MAX1668 slave address. The

default address is 1001 101 (ADD0 = ADD1 = VCC).

JU1 corresponds to ADD0, and JU2 corresponds to

ADD1; see Table 1 for a complete list of addresses.

The MAX1668 must undergo a power-on reset for the

new address to become effective.

The +5V supply voltage for the MAX1668 comes from

the SMBus interface board. To evaluate the MAX1668

with a different voltage, cut the trace shorting the two

JU4 pins and apply a voltage to the VCC pad.

The MAX1668 can be placed in standby mode using

jumper JU3. See Table 2 for jumper setting.

A slide switch, SW1, is provided as a means to force a

power-on reset of the MAX1668. This switch disables

power to the device.

Table 1. JU1 and JU2 Shunt Settings for

SMBus Address

Table 2. JU3 Shunt Settings for STBY

*Default

*Default

SHUNT

LOCATION

MAX1668 ADDRESS

JU1

JU2

BINARY

HEX

2-3

2-3

0011 000

0x30

2-3

Open

0011 001

0x32

2-3

1-2

0011 010

0x34

Open

2-3

0101 001

0x52

Open

Open

0101 010

0x54

Open

1-2

0101 011

0x56

1-2

2-3

1001 100

0x98

1-2

Open

1001 101

0x9A

1-2*

1-2*

1001 110

0x9C

SHUNT

LOCATION

STBY PIN

FUNCTION

1-2*

Connected to VCC

In operating mode

Open

Connect an external

signal to

STBY pin

2-3

Connected to GND

In standby mode