Rainbow Electronics MAX6692 User Manual

General Description

The MAX6648/MAX6692 are precise, two-channel digi­tal temperature sensors. They accurately measure the
temperature of their own die and a remote PN junction,
and report the temperature in digital form using a 2-wire
serial interface. The remote PN junction is typically the
emitter-base junction of a common-collector PNP on a
CPU, FPGA, or ASIC.

The 2-wire serial interface accepts standard System
Management Bus (SMBus)™ write byte, read byte,
send byte, and receive byte commands to read the
temperature data and to program the alarm thresholds.
To enhance system reliability, the MAX6648/MAX6692
include an SMBus timeout. A fault queue prevents the
ALERT and OVERT outputs from setting until a fault has
been detected one, two, or three consecutive times
(programmable).

The MAX6648/MAX6692 provide two system alarms:
ALERT and OVERT. ALERT asserts when any of four tem­perature conditions are violated: local overtemperature,
remote overtemperature, local undertemperature, or
remote undertemperature. OVERT asserts when the tem­perature rises above the value in either of the two OVERT
limit registers. The OVERT output can be used to activate
a cooling fan, or to trigger a system shutdown.

Measurements can be done autonomously, with the
conversion rate programmed by the user, or in a single­shot mode. The adjustable conversion rate allows the
user to optimize supply current and temperature
update rate to match system needs.

Remote accuracy is ±0.8°C maximum error between
+25°C and +125°C with no calibration needed. The
MAX6648/MAX6692 operate from -55°C to +125°C, and
measure temperatures between 0°C and +125°C. The
MAX6648 is available in an 8-pin µMAX package, and the
MAX6692 is available in 8-pin µMAX and SO packages.

Applications

Desktop Computers

Notebook Computers

Servers

Thin Clients

Workstations

Test and Measurement

Multichip Modules

Features

♦ Dual Channel: Measures Remote and Local

Temperature

♦ 0.125°C Resolution

♦ High Accuracy: ±0.8°C (max) from +25°C to

+125°C (Remote), and ±2°C (max) from +60°C to
+100°C (Local)

♦ Two Alarm Outputs: ALERT and OVERT
♦ Two Default OVERT Thresholds Available

MAX6648: +110°C
MAX6692: +85°C

♦ Programmable Conversion Rate

♦ SMBus-Compatible Interface

♦ SMBus Timeout

♦ Programmable Under/Overtemperature Alarm

Thresholds

MAX6648/MAX6692

Precision SMBus-Compatible Remote/Local

Temperature Sensors with Overtemperature Alarms

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

V

CC

DXP

DXN

10kΩ EACH

CLOCK

TO FAN DRIVER OR
SYSTEM SHUTDOWN

3.3V

DATA

INTERRUPTED TO µP

200Ω

0.1µF

SDA

SCLK

ALERT

GND

2200pF

µP

MAX6648
MAX6692

OVERT

Typical Operating Circuit

19-2545; Rev 0; 8/02

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

PART

TEMP RANGE

PIN-

MEASURED

TEMP RANGE

MAX6648MUA*

8 µMAX

0°C to +125°C

MAX6692MUA

8 µMAX

0°C to +125°C

MAX6692MSA

8 SO

0°C to +125°C

SMBus is a trademark of Intel Corp.

Pin Configuration and Functional Diagram appear at end of
data sheet.

*Future product—contact factory for availability.

PACKAGE

-55°C to +125°C

-55°C to +125°C

-55°C to +125°C

MAX6648/MAX6692

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

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

All Voltages Referenced to GND
V

CC

...........................................................................-0.3V to +6V

DXP.............................................................-0.3V to (V

CC

+ 0.3V)

DXN .......................................................................-0.3V to +0.8V

SCLK, SDA, ALERT, OVERT.....................................-0.3V to +6V

SDA, ALERT, OVERT Current .............................-1mA to +50mA

DXN Current .......................................................................±1mA

Continuous Power Dissipation (T

A

= +70°C)

8-Pin µMAX (derate 5.9mW/°C above +70°C) .............471mW

8-Pin SO (derate 5.9mW/°C above +70°C)..................471mW

ESD Protection (all pins, Human Body Model) ................±2000V

Junction Temperature......................................................+150°C

Operating Temperature Range .........................-55°C to +125°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

ELECTRICAL CHARACTERISTICS

(VCC= 3.0V to 5.5V, TA= -55°C to +125°C, unless otherwise specified. Typical values are at VCC= 3.3V and TA= +85°C.) (Note 1)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Supply Voltage V

CC

3.0 5.5 V

°C

Temperature Resolution

10 Bits

V

CC

= 3.3V,

T

A

= +85°C

V

CC

= 3.3V,

+60°C ≤ T

A

≤

+100°C

TRJ = 0°C to +125°C

Remote Temperature Error

V

CC

= 3.3V, +0°C

≤ T

A

≤ +100°C

T

RJ

= 0°C to +125°C

°C

TA = +60°C to +100°C

Local Temperature Error V

CC

= 3.3V

T

A

= 0°C to +125°C

°C

Supply Sensitivity of Temperature
Error

°C/V

Undervoltage Lockout (UVLO)
Threshold

UVLO Falling edge of V

CC

disables ADC 2.4 2.7

V

UVLO Hysteresis 90 mV

Power-On-Reset (POR) Threshold

VCC falling edge 2.0 V

POR Threshold Hysteresis 90 mV

Standby Supply Current SMBus static 3.5 12 µA

Operating Current During conversion

0.8 mA

0.25 conversions per second 40 80

Average Operating Current

2 conversions per second

400

µA

Conversion Time t

CONV

From stop bit to conversion completion 95

156 ms

Conversion Time Error -25

%

DXP and DXN Leakage Current Standby mode 100 nA

High level 80

120

Remote-Diode Source Current I

RJ

Low level 8 10 12

µA

0.125

TRJ = +25°C to +125°C -0.8 +0.8

TRJ = +60°C to +100°C -1.0 +1.0

-1.6 +1.6

-3.0 +3.0

-2.0 +2.0

-3.0 +3.0

±0.2

0.45

250

125

100

2.95

+25

MAX6648/MAX6692

Precision SMBus-Compatible Remote/Local

Temperature Sensors with Overtemperature Alarms

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= 3.0V to 5.5V, TA= -55°C to +125°C, unless otherwise specified. Typical values are at VCC= 3.3V and TA= +85°C.) (Note 1)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

ALERT, OVERT

I

SINK

= 1mA 0.4

Output Low Voltage

I

SINK

= 4mA 0.6

V

Output High Leakage Current VOH = 5.5V 1 µA

SMBus-COMPATIBLE INTERFACE (SCLK AND SDA)

Logic Input Low Voltage V

IL

0.8 V

VCC = 3.0V 2.2

Logic Input High Voltage V

IH

VCC = 5.5V 2.6

V

Input Leakage Current I

LEAK

VIN = GND or V

CC

-1 +1 µA

Output Low-Sink Current I

SINK

VOL = 0.6V 6 mA

Input Capacitance C

IN

5pF

SMBus-COMPATIBLE TIMING (Note 2)

Serial Clock Frequency f

SCLK

(Note 3) 100 kHz

Bus Free Time Between STOP
and START Condition

t

BUF

4.7 µs

START Condition Setup Time 4.7 µs

Repeat START Condition Setup
Time

t

SU:STA

90% to 90% 50 ns

START Condition Hold Time

10% of SDA to 90% of SCLK 4 µs

STOP Condition Setup Time

90% of SCLK to 90% of SDA 4 µs

Clock Low Period t

LOW

10% to 10% 4.7 µs

Clock High Period t

HIGH

90% to 90% 4 µs

Data Setup Time

(Note 4) 250 µs

Receive SCLK/SDA Rise Time t

R

1µs

Receive SCLK/SDA Fall Time t

F

300 ns

t

SP

050ns

SMBus Timeout

SDA low period for interface reset 25 37 45 ms

Note 1: All parameters tested at a single temperature. Specifications over temperature are guaranteed by design.
Note 2: Timing specifications guaranteed by design.
Note 3: The serial interface resets when SCLK is low for more than t

TIMEOUT

.

Note 4: A transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SCLK’s falling edge.

t

Pulse Width of Spike Suppressed

HD:STA

t

SU:STO

t

HD:DAT

t

TIMEOUT

MAX6648/MAX6692

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

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VCC= 3.3V, TA= +25°C, unless otherwise noted.)

STANDBY SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX6648/92 toc01

SUPPLY VOLTAGE (V)

STANDBY SUPPLY CURRENT (µA)

5.04.54.03.5

2.8

3.2

3.6

4.0

2.4

3.0 5.5

OPERATING SUPPLY CURRENT

vs. CONVERSION RATE

MAX6648/92 toc02

CONVERSION RATE (Hz)

OPERATING SUPPLY CURRENT (µA)

4.002.001.000.500.250.13

100

200

300

400

500

600

0

0.63

REMOTE TEMPERATURE ERROR

vs. REMOTE-DIODE TEMPERATURE

MAX6648/92 toc03

TEMPERATURE (°C)

TEMPERATURE ERROR (°C)

100755025

-1.5

-0.5

0.5

1.5

2.5

-2.5
0 125

TA = +85°C
FAIRCHILD 2N3906

LOCAL TEMPERATURE ERROR

vs. DIE TEMPERATURE

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1.0

-1.0

MAX6648/92 toc04

TEMPERATURE (°C)

TEMPERATURE ERROR (°C)

1007550250 125

TEMPERATURE ERROR

vs. POWER-SUPPLY NOISE FREQUENCY

MAX6648/92 toc05

FREQUENCY (Hz)

TEMPERATURE ERROR (°C)

10k1k1 10 100

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0

0.1 100k

LOCAL ERROR

REMOTE ERROR

VIN = SQUARE WAVE APPLIED TO VCC
WITH NO 0.1µF V

CC

CAPACITOR

-1

0

1

2

3

4

5

6

7

8

9

-2

TEMPERATURE ERROR

vs. COMMON-MODE NOISE FREQUENCY

MAX6648/92 toc06

FREQUENCY (Hz)

TEMPERATURE ERROR (°C)

100k10k10 100 1k1

REMOTE ERROR

LOCAL ERROR

V

IN

= AC-COUPLED TO DXN

V

IN

= 100mV

P-P

-1.5

-1.0

-0.5

0

0.5

1.0

1.5

2.0

-2.0

TEMPERATURE ERROR

vs. DIFFERENTIAL-MODE NOISE FREQUENCY

MAX6648/92 toc07

FREQUENCY (Hz)

TEMPERATURE ERROR (°C)

100k10k10 100 1k1

VIN = 20mV

P-P

SQUARE WAVE

APPLIED TO DXP-DXN

TEMPERATURE ERROR

vs. DXP-DXN CAPACITANCE

MAX6648/92 toc08

DXP-DXN CAPACITANCE (nF)

TEMPERATURE ERROR (°C)

10.0001.000

-5

-4

-3

-2

-1

0

1

-6

0.100 100.000

MAX6648/MAX6692

Precision SMBus-Compatible Remote/Local

Temperature Sensors with Overtemperature Alarms

_______________________________________________________________________________________ 5

Detailed Description

The MAX6648/MAX6692 are temperature sensors
designed to work in conjunction with a microprocessor
or other intelligence in thermostatic, process-control, or
monitoring applications. Communication with the
MAX6648/MAX6692 occurs through the SMBus-com­patible serial interface and dedicated alert pins. ALERT
asserts if the measured local or remote temperature is
greater than the software-programmed ALERT high
limit or less than the ALERT low limit. ALERT also
asserts if the remote-sensing diode pins are shorted or
unconnected. The overtemperature alarm, OVERT,
asserts if the software-programmed OVERT limit is
exceeded. OVERT can be connected to fans, a system
shutdown, a clock throttle control, or other thermal­management circuitry.

The MAX6648/MAX6692 convert temperatures to digital
data either at a programmed rate or in single conver­sions. Temperature data is represented as 10 bits plus
sign, with the LSB equal to 0.125°C. The “main” tempera­ture data registers (at addresses 00h and 01h) are 8-bit
registers that represent the data as 7 bits with the final
MSB indicating the diode fault status (Table 1). The
remaining 3 bits of temperature data are available in the
“extended” registers at addresses 11h and 10h (Table 2).

ADC and Multiplexer

The averaging ADC integrates over a 60ms period
(each channel, typically), with excellent noise rejection.
The multiplexer automatically steers bias currents
through the remote and local diodes. The ADC and
associated circuitry measure each diode’s forward volt-
age and compute the temperature based on this volt­age. Both channels are automatically converted once
the conversion process has started, either in free-run­ning or single-shot mode. If one of the two channels is
not used, the device still performs both measurements,
and the user can ignore the results of the unused chan-

Pin Description

PIN NAME FUNCTION

1V

CC

Supply Voltage Input, 3V to 5.5V. Bypass V

CC

to GND with a 0.1µF capacitor. A 200Ω series

resistor is recommended but not required for additional noise filtering.

2 DXP

Combined Remote-Diode Current Source and A/D Positive Input for Remote-Diode Channel. DO
NOT LEAVE DXP FLOATING; tie DXP to DXN if no remote diode is used. Place a 2200pF
capacitor between DXP and DXN for noise filtering.

3 DXN

Combined Remote-Diode Current Sink and A/D Negative Input. DXN is internally biased to one
diode drop above ground.

4 OVERT

Overtemperature Alert/Interrupt Output, Open Drain. OVERT is logic low when the temperature is
above the software-programmed threshold.

5 GND Ground

6 ALERT

SMBus Alert (Interrupt) Output, Open Drain. ALERT asserts when temperature exceeds user-set
limits (high or low temperature). ALERT stays asserted until acknowledged by either reading the
status register or by successfully responding to an alert response address, provided that the fault
condition no longer exists. See the

ALERT

Interrupts section.

7 SDA SMBus Serial-Data Input/Output, Open Drain

8 SCLK SMBus Serial-Clock Input

Table 1. Main Temperature Data Register
Format (00h, 01h)

TEMP (°C) DIGITAL OUTPUT

130 0 111 1111

127 0 111 1111

126 0 111 1111

25 0 001 1001

0 0 000 0000

<0 0 000 0000

-1 0 000 0000

-25 0 000 0000

Diode fault

(short or open)

1 000 0000

MAX6648/MAX6692

nel. If the remote-diode channel is unused, connect
DXP to DXN rather than leaving the pins open.

The DXN input is biased to one VBEabove ground by
an internal diode to prepare the ADC inputs for a differ­ential measurement. The worst-case DXP-DXN differen­tial input voltage range is 0.25V to 0.95V. Excess
resistance in series with the remote diode causes
+0.5°C (typ) error per ohm.

A/D Conversion Sequence

A conversion sequence consists of a local temperature
measurement and a remote temperature measurement.
Each time a conversion begins, whether initiated auto­matically in the free-running autonomous mode (RUN = 0)
or by writing a one-shot command, both channels are
converted, and the results of both measurements are
available after the end of a conversion. A BUSY status bit
in the status byte indicates that the device is performing a
new conversion. The results of the previous conversion
are always available, even if the ADC is busy.

Low-Power Standby Mode

Standby mode reduces the supply current to less than
10µA by disabling the ADC and timing circuitry. Enter
standby mode by setting the RUN bit to 1 in the configu­ration byte register (Table 6). All data is retained in mem­ory, and the SMBus interface is active and listening for
SMBus commands. Standby mode is not a shutdown
mode. With activity on the SMBus, the device draws more
supply current (see Typical Operating Characteristics). In
standby mode, the MAX6648/MAX6692 can be forced to
perform A/D conversions through the one-shot command,
regardless of the RUN bit status.

If a 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 a tempera­ture register. The previous data is not changed and
remains available.

Supply-current drain during the 125ms conversion peri­od is 500µA (typ). Slowing down the conversion rate
reduces the average supply current (see Typical
Operating Characteristics). Between conversions, the
conversion rate timer consumes about 25µA of supply
current. In standby mode, supply current drops to
about 3µA.

SMBus Digital Interface

From a software perspective, the MAX6648/MAX6692
appear as a set of byte-wide registers that contain tem­perature data, alarm threshold values, and control bits.
A standard SMBus-compatible 2-wire serial interface is
used to read temperature data and write control bits
and alarm threshold data. These devices respond to the
same SMBus slave address for access to all functions.

The MAX6648/MAX6692 employ four standard SMBus
protocols: write byte, read byte, send byte, and receive
byte (Figures 1, 2, and 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 when using the shorter protocols
in multimaster systems, as a second master could over­write the command byte without informing the first master.

Temperature data can be read from the read internal
temperature (00h) and read external temperature (01h)
registers. The temperature data format for these regis­ters is 7 bits plus 1 bit, indicating the diode fault status
for each channel, with the LSB representing 1°C (Table

1). The MSB is transmitted first.

An additional 3 bits can be read from the read external
extended temperature register (10h), which extends the
data to 10 bits plus sign and the resolution to 0.125°C
per LSB (Table 2). An additional 3 bits can be read
from the read internal extended temperature register
(11h), which extends the data to 10 bits (plus 1 bit indi­cating the diode fault status) and the resolution to

0.125°C per LSB (Table 2).

When a conversion is complete, the main temperature
register and the extended temperature register are
updated simultaneously. Ensure that no conversions
are completed between reading the main register and
the extended register, so that both registers contain the
result of the same conversion.

To ensure valid extended data, read extended resolu­tion temperature data using one of the following
approaches:

1) Put the MAX6648/MAX6692 into standby mode by
setting bit 6 of the configuration register to 1. Initiate
a one-shot conversion using command byte 0Fh.
When this conversion is complete, read the contents
of the temperature data registers.

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

6 _______________________________________________________________________________________

FRACTIONAL TEMP (°C) DIGITAL OUTPUT

0.000 000X XXXX

0.125 001X XXXX

0.250 010X XXXX

0.375 011X XXXX

0.500 100X XXXX

0.625 101X XXXX

0.750 110X XXXX

0.875 111X XXXX

Table 2. Extended Resolution Temperature
Register Data Format (10h, 11h)