MAX1617AMEE Datasheet MAX1617MEE, MAX1617AMEE, MAX1617MEE+T | P10-P12

Remote/Local Temperature Sensor

with SMBus Serial Interface

MAX1617

Maxim Integrated

the MAX1617 can be forced to perform A/D conversions

via the one-shot command, despite the RUN/STOP bit

being high.

Activate hardware standby mode by forcing the STBY

pin low. In a notebook computer, this line may be con-

nected to the system SUSTAT# suspend-state signal.

The STBY pin low state overrides any software conversion

command. If a hardware or software standby command is

received while a conversion is in progress, the conversion

cycle is truncated, and the data from that conversion is not

latched into either temperature reading register. The previ-

ous data is not changed and remains available.

Supply-current drain during the 125ms conversion peri-

od is always about 450µA. Slowing down the conver-

sion rate reduces the average supply current (see

Typical Operating Characteristics). In between conver-

sions, the instantaneous supply current is about 25µA

due to the current consumed by the conversion rate

timer. In standby mode, supply current drops to about

3µA. At very low supply voltages (under the power-on-

reset threshold), the supply current is higher due to the

address pin bias currents. It can be as high as 100µA,

depending on ADD0 and ADD1 settings.

SMBus Digital Interface

From a software perspective, the MAX1617 appears as a

set of byte-wide registers that contain temperature data,

alarm threshold values, or control bits. A standard

SMBus 2-wire serial interface is used to read tempera-

ture data and write control bits and alarm threshold data.

Each A/D channel within the device responds to the

same SMBus slave address for normal reads and writes.

The MAX1617 employs four standard SMBus protocols:

Write Byte, Read Byte, Send Byte, and Receive Byte

(Figure 3). The shorter Receive Byte protocol allows

quicker transfers, provided that the correct data register

was previously selected by a Read Byte instruction. Use

caution with the shorter protocols in multi-master systems,

since a second master could overwrite the command

byte without informing the first master.

The temperature data format is 7 bits plus sign in twos-com-

plement form for each channel, with each data bit repre-

senting 1°C (Table 2), transmitted MSB first. Measurements

are offset by +1/2°C to minimize internal rounding errors; for

example, +99.6°C is reported as +100°C.

MAX1617

ACK

7 bits

ADDRESS ACKWR

8 bits

DATA ACK

8 bits

S COMMAND

Write Byte Format

Read Byte Format

Send Byte Format Receive Byte Format

Slave Address: equiva-

lent to chip-select line of

a 3-wire interface

Command Byte: selects which

Data Byte: data goes into the register

set by the command byte (to set

thresholds, configuration masks, and

sampling rate)

ACK

7 bits

ADDRESS ACKWR S ACK

8 bits

DATA

7 bits

ADDRESS RD

8 bits

/// PS COMMAND

Slave Address: equiva-

lent to chip-select line

Command Byte: selects

which register you are

reading from

Slave Address: repeated

due to change in data-

flow direction

Data Byte: reads from

the register set by the

command byte

ACK

7 bits

ADDRESS WR

8 bits

COMMAND ACK PS ACK

7 bits

ADDRESS RD

8 bits

DATA /// PS

Command Byte: sends com-

mand with no data, usually

used for one-shot command

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

S = Start condition Shaded = Slave transmission

P = Stop condition /// = Not acknowledged

Figure 3. SMBus Protocols

Remote/Local Temperature Sensor

with SMBus Serial Interface

MAX1617

Maxim Integrated

Alarm Threshold Registers

Four registers store alarm threshold data, with high-

temperature (T

HIGH

) and low-temperature (T

LOW

) reg-

isters for each A/D channel. If either measured

temperature equals or exceeds the corresponding

alarm threshold value, an ALERT interrupt is asserted.

The power-on-reset (POR) state of both T

HIGH

registers

is full scale (0111 1111, or +127°C). The POR state of

both T

LOW

registers is 1100 1001 or -55°C.

Diode Fault Alarm

There is a continuity fault detector at DXP that detects

whether the remote diode has an open-circuit condi-

tion. At the beginning of each conversion, the diode

fault is checked, and the status byte is updated. This

fault detector is a simple voltage detector; if DXP rises

above V

- 1V (typical) due to the diode current

source, a fault is detected. Note that the diode fault

isn’t checked until a conversion is initiated, so immedi-

ately after power-on reset the status byte indicates no

fault is present, even if the diode path is broken.

If the remote channel is shorted (DXP to DXN or DXP to

GND), the ADC reads 0000 0000 so as not to trip either

the T

HIGH

or T

LOW

alarms at their POR settings. In

applications that are never subjected to 0°C in normal

operation, a 0000 0000 result can be checked to indi-

cate a fault condition in which DXP is accidentally short

circuited. Similarly, if DXP is short circuited to V

, the

ADC reads +127°C for both remote and local channels,

and the device alarms.

AALLEERRTT

Interrupts

The ALERT interrupt output signal is latched and can

only be cleared by reading the Alert Response address.

Interrupts are generated in response to T

HIGH

and T

LOW

comparisons and when the remote diode is disconnect-

ed (for continuity fault detection). The interrupt does not

halt automatic conversions; new temperature data con-

tinues to be available over the SMBus interface after

ALERT is asserted. The interrupt output pin is open-drain

so that devices can share a common interrupt line. The

interrupt rate can never exceed the conversion rate.

The interface responds to the SMBus Alert Response

address, an interrupt pointer return-address feature

(see Alert Response Address section). Prior to taking

corrective action, always check to ensure that an inter-

rupt is valid by reading the current temperature.

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). Then

any slave device that generated an interrupt attempts

to identify itself by putting its own address on the bus

(Table 3).

0 111 1111

DIGITAL OUTPUT

DATA BITS

SIGN MSB LSB

0 111 1111+127+127.00

0 111 1111

0 111 1110+126+126.00

+127+126.50

0 001 1001

0 000 0001+1+0.50

0 000 0000

0 000 0000+0+0.00

+127+130.00

+0+0.25

+25+25.25

0 000 0000

0 000 0000+0-0.50

1 111 1111

1 111 1111-1-1.00

TEMP.

(°C)

-1-0.75

1 110 0111

1 110 0110-25-25.50

1 100 1001

ROUNDED

TEMP.

(°C)

1 100 1001-55-55.00

+0-0.25

-55-54.75

-25-25.00

1 011 1111

1 011 1111-65-70.00

-65-65.00

Table 2. Data Format (Twos-Complement) Table 3. Read Format for Alert Response

Address (0001100)

ADD66

Provide the current MAX1617

slave address that was latched at

POR (Table 8)

FUNCTION

ADD55

ADD44

ADD33

ADD22

ADD11

ADD7

(MSB)

(LSB)

Logic 1

BIT NAME

Remote/Local Temperature Sensor

with SMBus Serial Interface

MAX1617

Maxim Integrated

The Alert Response can activate several different slave

devices simultaneously, similar to the I

C General Call.

If more than one slave attempts to respond, bus arbitra-

tion rules apply, and the device with the lower address

code wins. The losing device does not generate an

acknowledge and continues to hold the ALERT line low

until serviced (implies that the host interrupt input is

level-sensitive). Successful reading of the alert

response address clears the interrupt latch.

Command Byte Functions

The 8-bit command byte register (Table 4) is the master

index that points to the various other registers within the

MAX1617. The register’s POR state is 0000 0000, so

that a Receive Byte transmission (a protocol that lacks

the command byte) that occurs immediately after POR

returns the current local temperature data.

The one-shot command immediately forces a new conver-

sion cycle to begin. In software standby mode

(RUN/STOP bit = high), a new conversion is begun, after

which the device returns to standby mode. If a conversion

is in progress when a one-shot command is received, the

command is ignored. If a one-shot command is received

in auto-convert mode (RUN/STOP bit = low) between con-

versions, a new conversion begins, the conversion rate

timer is reset, and the next automatic conversion takes

place after a full delay elapses.

Configuration Byte Functions

The configuration byte register (Table 5) is used to

mask (disable) interrupts and to put the device in soft-

ware standby mode. The lower six bits are internally set

to (XX1111), making them “don’t care” bits. Write zeros

to these bits. This register’s contents can be read back

over the serial interface.

Status Byte Functions

The status byte register (Table 6) indicates which (if

any) temperature thresholds have been exceeded. This

byte also indicates whether or not the ADC is convert-

ing and whether there is an open circuit in the remote

diode DXP–DXN path. After POR, the normal state of all

the flag bits is zero, assuming none of the alarm condi-

tions are present. The status byte is cleared by any

successful read of the status byte, unless the fault per-

sists. Note that the ALERT interrupt latch is not auto-

matically cleared when the status flag bit is cleared.

When reading the status byte, you must check for inter-

nal bus collisions caused by asynchronous ADC timing,

or else disable the ADC prior to reading the status byte

(via the RUN/STOP bit in the configuration byte). In

one-shot mode, read the status byte only after the con-

version is complete, which is 150ms max after the one-

shot conversion is commanded.

Table 4. Command-Byte Bit Assignments

*If the device is in hardware standby mode at POR, both temperature registers read 0°C.

Read remote temperature: returns latest temperature

RRTE 01h

00h

COMMAND

0000 0000*

POR STATE

Read configuration byteRCL 03h

02h

0000 0000

N/A Read status byte (flags, busy signal)RSL

Read local T

HIGH

limitRLHN 05h

Read local temperature: returns latest temperatureRLTS

04h

0111 1111

0000 0010

Read remote T

HIGH

limitRRHI 07h

06h

0111 1111

1100 1001 Read local T

LOW

limitRLLI

Read conversion rate byte

RCRA

Write configuration byteWCA 09h

08h

N/A

1100 1001

FUNCTION

Write local T

HIGH

limitWLHO 0Bh

0Ah

N/A

N/A Write conversion rate byteWCRW

Write remote T

HIGH

limitWRHA 0Dh

Read remote T

LOW

limitRRLS

0Ch

N/A

One-shot command (use send-byte format)OSHT 0Fh

0Eh

N/A

N/A Write remote T

LOW

limitWRLN

Write local T

LOW

limitWLLM

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P20

MAX1617AMEE

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