MAX6692MSA(2002) Просмотр технического описания (PDF) - Maxim Integrated

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MAX6692MSA
(Rev.:2002)

Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms

Maxim Integrated 

Precision SMBus-Compatible Remote/Local

Temperature Sensors with Overtemperature Alarms

A

B

C

D

EF

G

tLOW tHIGH

SMBCLK

H

IJK

LM

SMBDATA

tSU:STA tHD:STA

tSU:DAT

A = START CONDITION

B = MSB OF ADDRESS CLOCKED INTO SLAVE

C = LSB OF ADDRESS CLOCKED INTO SLAVE

D = R/W BIT CLOCKED INTO SLAVE

E = SLAVE PULLS SMBDATA LINE LOW

F = ACKNOWLEDGE BIT CLOCKED INTO MASTER

G = MSB OF DATA CLOCKED INTO SLAVE

H = LSB OF DATA CLOCKED INTO SLAVE

Figure 3. SMBus Read Timing Diagram

tSU:STO tBUF

I = MASTER PULLS DATA LINE LOW

J = ACKNOWLEDGE CLOCKED INTO SLAVE

K = ACKNOWLEDGE CLOCK PULSE

L = STOP CONDITION

M = NEW START CONDITION

Alarm Threshold Registers

Four registers store ALERT threshold values—one high-

temperature (THIGH) and one low-temperature (TLOW)

register each for the local and remote channels. If

either measured temperature equals or exceeds the

corresponding ALERT threshold value, the ALERT inter-

rupt asserts.

The power-on-reset (POR) state of both ALERT THIGH

registers is full scale (0101 0101, or +85°C). The POR

state of both TLOW registers is 0000 0000, or 0°C.

Two additional registers store remote and local alarm

threshold data corresponding to the OVERT output. The

values stored in these registers are high-temperature

thresholds. If either of the measured temperatures

equals or exceeds the corresponding alarm threshold

value, an OVERT output asserts. The POR state of the

OVERT threshold is 0110 1110 or +110°C for the

MAX6648, and 0101 0101 or +85°C for the MAX6692.

Diode Fault Alarm

A continuity fault detector at DXP detects an open cir-

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

GND, or DXN. If an open or short circuit exists, the

external temperature register is loaded with 1000 0000.

If the fault is an open-circuit fault bit 2 (OPEN) of the

status byte, it is set to 1 and the ALERT condition is

activated at the end of the conversion. Immediately

after POR, the status register indicates that no fault is

present. If a fault is present upon power-up, the fault is

not indicated until the end of the first conversion.

ALERT Interrupts

The ALERT interrupt occurs when the internal or exter-

nal temperature reading exceeds a high- or low-tem-

perature limit (user programmed) or when the remote

diode is disconnected (for continuity fault detection).

The ALERT interrupt output signal is latched and can

be cleared only by either reading the status register or

by successfully responding to an alert response

address. In both cases, the alert is cleared only if the

fault condition no longer exists. Asserting ALERT does

not halt automatic conversion. The ALERT output pin is

open drain, allowing multiple devices to share a com-

mon interrupt line.

The MAX6648/MAX6692 respond to the SMBus alert

response address, an interrupt pointer return-address

feature (see the Alert Response Address section). Prior

to taking corrective action, always check to ensure that

an interrupt is valid by reading the current temperature.

Fault Queue Register

In some systems, it may be desirable to ignore a single

temperature measurement that falls outside the ALERT

limits. Bits 2 and 3 of the fault queue register (address

22h) determine the number of consecutive temperature

faults necessary to set ALERT (see Tables 3 and 4).

Alert Response Address

The SMBus alert response interrupt pointer provides

quick fault identification for simple slave devices that

lack the complex, expensive logic needed to be a bus

master. Upon receiving an ALERT interrupt signal, the

host master can broadcast a receive byte transmission

to the alert response slave address (0001 100).

Following such a broadcast, any slave device that gen-

erated an interrupt attempts to identify itself by putting

its own address on the bus.

The alert response can activate several different slave

devices simultaneously, similar to the I2C™ general call. If

more than one slave attempts to respond, bus arbitration

I2C is a trademark of Philips Corp.

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