MAX6638ATC 데이터 시트보기 (PDF) - Maxim Integrated

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MAX6638ATC

Temperature Monitor with Dual Serial Interface

Maxim Integrated 

Temperature Monitor with

Dual Serial Interface

threshold limit values, and control. A standard SMBus

2-wire serial interface is used to read temperature data,

write control bits, and set threshold data. The MAX6638

employs four standard SMBus protocols: write byte, read

byte, send byte, and receive byte (Figure 4).

Read the temperature data from the read internal tem-

perature (00h) and read external temperature (01h)

registers of each SMBus channel. The temperature

data format for these registers is 8 bits for each temper-

ature-sensor channel, with the LSB representing 1°C

(Table 1). The temperature data transmits MSB first.

The external extended-temperature register (10h) pro-

vides additional 3 bits, extending the data to 11 bits

and the resolution to 0.125°C per LSB (Table 2).

The main temperature register and the extended temper-

ature registers update simultaneously upon completion

of a conversion. To ensure the registers contain the

results of the same conversion of the main temperature

data (MSBs) and the extended temperature data (LSBs),

read the data before a new conversion completes.

Alarm-Threshold Registers

Four registers store ALERT threshold values: one high

temperature (THIGH_) and one low temperature

(TLOW_) limit register each for the local and remote

temperature sensors. If either measured temperature

equals or exceeds the corresponding ALERT_ thresh-

old value, the ALERT_ output asserts.

The MAX6638 local ALERT_ THIGH_ register POR state

is 0101 0101, which corresponds to +85°C, while the

remote ALERT_ THIGH_ register POR state is 0101

1111, which corresponds to +95°C. The POR state of

the local and remote TLOW_ registers for all devices is

0000 0000, corresponding to 0°C.

Two additional registers store remote and local alarm

threshold data corresponding to the OVERT1 output

accessible only through SMBus1. The MAX6638 stores

high-temperature thresholds in these registers. If either

of the measured temperatures equals or exceeds the

corresponding alarm threshold value, the OVERT1 out-

put asserts. The MAX6638 local OVERT1 register POR

state is 0101 0101, corresponding to +85°C, while the

remote OVERT1 register POR state is 0111 1101, corre-

sponding to +125°C.

Diode Fault

A continuity fault detector at DXP detects an open cir-

cuit between DXP and DXN, or a DXP short to VCC,

Write Byte Format

S

ADDRESS

WR

ACK

COMMAND

ACK

DATA

ACK

P

7 bits

Slave Address: equiva-

lent to chip-select line of

a 3-wire interface

Read Byte Format

8 bits

Command Byte: selects to

which register you are writing

8 bits

1

Data Byte: data goes into the register

set by the command byte (to set

thresholds, configuration masks, and

sampling rate)

S ADDRESS WR ACK COMMAND ACK S ADDRESS RD ACK DATA /// P

7 bits

8 bits

7 bits

8 bits

Slave Address: equiva-

lent to chip-select line

Command Byte: selects

from which register you

are reading

Slave Address: repeated

due to change in data-

flow direction

Data Byte: reads from

the register set by the

command byte

Send Byte Format

Receive Byte Format

S ADDRESS WR ACK COMMAND ACK P

S ADDRESS RD ACK DATA /// P

7 bits

S = Start condition

P = Stop condition

8 bits

Command Byte: sends com-

mand with no data, usually

used for one-shot command

Shaded = Slave transmission

/// = Not acknowledged

7 bits

8 bits

Data Byte: reads data from

the register commanded

by the last read byte or

write byte transmission;

also used for SMBus alert

response return address

Figure 4. SMBus Protocols

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