Rainbow Electronics MAX1618 User Manual

________________General Description

The MAX1618 precise digital thermometer reports the
temperature of a remote sensor. The remote sensor is a
diode-connected transistor—typically a low-cost, easily
mounted 2N3904 NPN type—that replaces conventional
thermistors or thermocouples. Remote accuracy is ±3°C
for multiple transistor manufacturers, with no calibration
needed. The MAX1618 can also measure the die temper­ature of other ICs, such as microprocessors, that contain
an on-chip, diode-connected transistor.

The 2-wire serial interface accepts standard System
Management Bus (SMBus™) Write Byte, Read Byte, Send
Byte, and Receive Byte commands to program the alarm
thresholds and to read temperature data. The data format
is 7 bits plus sign, with each bit corresponding to 1°C, in
two’s complement format. Measurements can be done
automatically and autonomously, with the 16Hz conversion
rate or programmed to operate in a single-shot mode.

The thermostat mode configures the ALERT output as an
interrupt or as a temperature reset that remains active only
while the temperature is above the maximum temperature
limit or below the minimum temperature limit. The ALERT
output polarity in thermostat mode can be configured for
active high or active low. Fan control is implemented using
this ALERT output.

The MAX1618 is available in a small (1.1mm high) 10-pin
µMAX package.

________________________Applications

Desktop and Notebook Central Office
Computers Telecom Equipment

Smart Battery Packs Test and Measurement

LAN Servers Multichip Modules

Industrial Controls

____________________________Features

♦ Single Channel: Measures Remote CPU

Temperature

♦ No Calibration Required

♦ SMBus 2-Wire Serial Interface

♦ Programmable Under/Overtemperature Alarms

♦ Overtemperature Output for Fan Control

(Thermostat Mode)

♦ Supports SMBus Alert Response Accuracy

±3°C (+60°C to +100°C)
±5°C (-55°C to +120°C)

♦ 3µA (typ) Standby Supply Current

♦ 900µA (max) Supply Current in Autoconvert Mode

♦ +3V to +5.5V Supply Range

♦ Small 10-Pin µMAX Package

MAX1618

†

Remote Temperature Sensor

with SMBus Serial Interface

________________________________________________________________ Maxim Integrated Products 1

___________________Pin Configuration

1

2

3

4

5

10

9

8

7

6

ALERT

SMBDATA

SMBCLK

STBYDXN

GND

ADD1

ADD0

MAX1618

µMAX

TOP VIEW

V

CC

DXP

Typical Operating Circuit

19-1495; Rev 1; 12/99

PART

MAX1618MUB -55°C to +125°C

TEMP. RANGE PIN-PACKAGE

10 µMAX

Ordering Information

SMBus is a trademark of Intel Corp.
†Patents Pending

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.

2N3904

0.1µF

2200pF

V

CC

MAX1618

DXP

DXN

ADD0 ADD1

SMBDATA

3V TO 5.5V

200Ω

STBY

SMBCLK

ALERT

GND

10k EACH

CLOCK

DATA

INTERRUPT
TO µC

Autoconvert
mode, average

MAX1618

Remote Temperature Sensor
with SMBus Serial Interface

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= +3.3V, configuration byte register = X8h, TA= 0°C to +85°C, unless otherwise noted.)

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.

VCCto GND..............................................................-0.3V to +6V

DXP, ADD_ to GND ....................................-0.3V to (V

CC

+ 0.3V)

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

SMBCLK, SMBDATA, ALERT, STBY to GND ...........-0.3V to +6V

SMBDATA Current.................................................-1mA to 50mA

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

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

Continuous Power Dissipation (T

A

= +70°C)

µMAX (derate 5.6mW/°C above +70°C) ....................444mW

Operating Temperature Range (extended)......-55°C to +125°C

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

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

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

CONDITIONSSYMBOL UNITSMIN TYP MAXPARAMETER

Monotonicity guaranteed Bits

8

Temperature Resolution
(Note 1)

V

CC

V

3 5.5

Supply-Voltage Range

TR= +60°C to +100°C

°C

-3 3

Temperature Error,
Remote Diode (Note 2)

mV

50

Undervoltage Lockout Hysteresis

VCCinput, disables A/D conversion,
rising edge

mV

50

POR Threshold Hysteresis

VCC, falling edge V

1 1.7 2.5

Power-On Reset Threshold

UVLO V

2.6 2.8 2.95

Undervoltage Lockout
Threshold

Hardware or software standby,
SMBCLK at 10kHz

µA

5

Standby Supply Current

From stop bit to conversion complete

SMBus static

t

CONV

ms

47 62 78

Conversion Time

µA

450 900

Average Operating
Supply Current

µA

80 100 120

Remote-Diode Source Current

Autoconvert mode

V

0.7

DXN Source Voltage

81012

%

-25 25

Conversion Rate Timing Error

µA

310

Standby Supply Current

VCC= 3.0V to 5.5V

Momentary upon power-on reset

V

IL

V

0.8

STBY,

SMBCLK, SMBDATA

Input Low Voltage

VCC= 3.0V V

IH

V

2.2

STBY SMBCLK, SMBDATA
Input High Voltage

SMBCLK, SMBDATA forced to 0.4V mA

6

SMBCLK, SMBDATA
Output Low Sink Current

Logic inputs forced to VCCor GND µA

-1 1

STBY,

SMBCLK, SMBDATA

Input Current

µA

160

ADDO, ADD1 Bias Current

TR= +55°C to +125°C

-5 5

Autoconvert mode, average measured over
4sec, 16 conv/sec

DXP forced to DXN + 0.65V,
ID = 1 (high)

High level

Low level

SMBus INTERFACE

ADC AND POWER SUPPLY

MAX1618

Remote Temperature Sensor

with SMBus Serial Interface

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +3.3V, configuration byte register = X8h, TA= 0°C to +85°C, unless otherwise noted.)

ELECTRICAL CHARACTERISTICS

(VCC= +3.3V, configuration byte register = X8h, TA= -55°C to +125°C, unless otherwise noted.) (Note 5)

CONDITIONS

Monotonicity guaranteed

TR= +60°C to +100°C

Bits8Temperature Resolution (Note 1)

-3 3

TR= -55°C to +125°C

°C

-5 5

Initial Temperature Error,
Remote Diode (Note 2)

V3 5.5Supply-Voltage Range

From stop bit to conversion complete

Autoconvert mode

ms47 62 78Conversion Time

%-25 25Conversion-Rate Timing Error

UNITSMIN TYP MAXPARAMETER

CONDITIONSSYMBOL

ALERT forced to 5.5V

µA

1

ALERT Output High
Leakage Current

ALERT forced to 0.4V

mA

6

ALERT Output Low Sink Current

UNITSMIN TYP MAXPARAMETER

(Note 3) kHz

DC 100

SMBus Clock Frequency

90% to 90% points t

HIGH

µs

4

SMBCLK Clock High Time

10% to 10% points t

LOW

µs4.7SMBCLK Clock Low Time

90% to 10% pointst

F

ns

300

SMBCLK, SMBDATA Fall Time

90% to 90% points

10% to 90% points

t

SU:STA

ns

500

SMBus Repeated Start
Condition Setup Time

µs

4.7

SMBus Start Condition
Setup Time

t

R

µs

1

SMBCLK, SMBDATA Rise Time

pF

5

SMBCLK, SMBDATA Input
Capacitance

90% of SMBCLK to 10% of SMBDATAt

SU:STO

µs

4

SMBus Stop Condition
Setup Time

(Note 4)

10% of SMBDATA to 90% of SMBCLK

t

HD:DAT

µs

0

SMBus Data-Hold Time

90% of SMBDATA to 10% of SMBCLKt

SU:DAT

ns

250

SMBus Data Valid to SMBCLK
Rising-Edge Time

t

HD:STA

µs

4

SMBus Start Condition
Hold Time

Master clocking in data µs

1

SMBCLK Falling Edge to SMBus
Data-Valid Time

Between start/stop condition t

BUF

µs

4.7

SMBus Bus Free Time

V

CC

t

CONV

SYMBOL

40

-40
1 100

TEMPERATURE ERROR

vs. LEAKAGE RESISTANCE

-20

-30

-10

0

10

20

30

MAX1618 toc01

LEAKAGE RESISTANCE (MΩ)

TEMPERATURE ERROR (°C)

10

PATH = DXP TO GND AND CONFIG = H00

PATH = DXP TO GND AND CONFIG = H08

PATH = DXP TO VCC (5.0V)
AND CONFIG = H08

PATH = DXP TO VCC (5.0V)
AND CONFIG = H00

-8

-5

-6

-7

-4

-3

-2

-1

0

1

2

0.005 0.05 0.5 5 50

TEMPERATURE ERROR vs.

POWER-SUPPLY NOISE FREQUENCY

MAX1618 toc03

POWER-SUPPLY NOISE FREQUENCY (MHz)

TEMPERATURE ERROR (°C)

VIN = SQUARE WAVE APPLIED TO
V

CC

WITH NO 0.1µF VCC CAPACITOR

VIN = 100mVp-p

VIN = 250mVp-p

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

-1.00

0.00

-0.50

1.00

0.50

2.00

1.50

2.50

-55 -15 5-35 25 45 65 85 105 125

TEMPERATURE ERROR

vs. REMOTE-DIODE TEMPERATURE

MAX1618 toc02

TEMPERATURE (°C)

TEMPERATURE ERROR (°C)

CENTRAL CMPT3904
RANDOM SAMPLE

MAX1618

Remote Temperature Sensor
with SMBus Serial Interface

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +3.3V, configuration byte register = X8h, TA= -55°C to +125°C, unless otherwise noted.) (Note 5)

Note 1: Guaranteed, but not 100% tested.
Note 2: A remote diode is any diode-connected transistor from Table 7. T

R

is the junction temperature of the remote diode. See
Remote Diode Selection for remote-diode forward voltage requirements. Temperature specification guaranteed for a diode
with ideality factor (M

TR

= 1.013). Additional error = (1.013/M - 1) ✕273 + Temp where M = Ideality of remote diode used.

Note 3: The SMBus logic block is a static design that works with clock frequencies down to DC. While slow operation is possible, it

violates the 10kHz minimum clock frequency and SMBus specifications and may monopolize the bus.

Note 4: Note that a transition must internally provide at least a hold time to bridge the undefined region (300ns max) of SMBCLK’s

falling edge.

Note 5: Specifications from -55°C to +125°C are guaranteed by design, not production tested.

CONDITIONS UNITSMIN TYP MAXPARAMETER

VCC= 3.0V 2.2

STBY, SMBCLK, SMBDATA
Input High Voltage

V

2.4

ALERT forced to 0.4V

mA1

ALERT Output Low Sink Current

VCC= 5.5V

VCC= 3.0V to 5.5V 0.8

STBY, SMBCLK, SMBDATA
Input Low Voltage

V

Logic inputs forced to VCCor GND -2 2

STBY, SMBCLK, SMBDATA
Input Current

µA

SMBCLK, SMBDATA forced to 0.6V 6

SMBCLK, SMBDATA Output
Low Sink Current

mA

ALERT forced to 5.5V

µA1

ALERT Output High Leakage
Current

SMBus INTERFACE

MAX1618

Remote Temperature Sensor

with SMBus Serial Interface

_______________________________________________________________________________________ 5

____________________________Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

120

100

80

60

40

TEMPERATURE ERROR (°C)

20

TEMPERATURE ERROR vs.

COMMON-MODE NOISE FREQUENCY

AC-COUPLED TO DXN
2200pF DXN-DXP CAPACITOR

VIN = 100mVp-p

VIN = 50mVp-p

0

10 100 1000

COMMON-MODE NOISE FREQUENCY (MHz)

MAX1618 toc04

STANDBY SUPPLY CURRENT

vs. CLOCK FREQUENCY

50

40

30

VCC = 5V

TEMPERATURE ERROR

vs. DXP-DXN CAPACITANCE

0

-10

TEMPERATURE ERROR (°C)

-20
0806020 40 100

DXP-DXN CAPACITANCE (nF)

MAX1618 toc06

VCC = 5V

MAX1618 toc05

20

10

STANDBY SUPPLY CURRENT (µA)

0

1 10 100 1000

CLOCK FREQUENCY (kHz)

VCC = 3.3V

STANDBY SUPPLY CURRENT

100

90

80

70

60

50

40

30

20

STANDBY SUPPLY CURRENT (µA)

10

0

vs. SUPPLY VOLTAGE

ADD0, ADD1 = GND

ADD0, ADD1 = HIGH-Z

021 345

SUPPLY VOLTAGE (V)

MAX1618 toc07

TEMPERATURE (°C)

RESPONSE TO THERMAL SHOCK

120

110

100

90

80

70

60

50

40

30

20

-2 2 40 6 8 101214161820

10-PIN µMAX IMMERSED IN
+115°C FLUORINERT BATH

TIME (sec)

MAX1618 toc08

MAX1618

Remote Temperature Sensor
with SMBus Serial Interface

6 _______________________________________________________________________________________

Pin Description

Detailed Description

The MAX1618 is a temperature sensor designed to
work in conjunction with an external microcontroller
(µC) or other intelligence in thermostatic, process-con­trol, or monitoring applications. The µC is typically a
power-management or keyboard controller, generating
SMBus serial commands by “bit-banging” general-pur­pose input-output (GPIO) pins or through a dedicated
SMBus interface block.

Essentially an 8-bit serial analog-to-digital converter
(ADC) with a sophisticated front end, the MAX1618
contains a switched-current source, a multiplexer, an
ADC, an SMBus interface, and the associated control
logic (Figure 1). Temperature data from the ADC is
loaded into a data register, where it is automatically
compared with data previously stored in over/under­temperature alarm threshold registers. The alarm
threshold registers can be set for hysteretic fan control.

ADC and Multiplexer

The averaging ADC integrates over a 30ms period (typ)
with excellent noise rejection. The ADC converts at a
rate of 16Hz. The multiplexer automatically steers bias

currents through the remote diode, measures the for­ward voltage, and computes the temperature.

The DXN input is biased at 0.65V above ground by an
internal diode to set up the analog-to-digital (A/D)
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 about +1/2°C error/Ω. A 200µV offset voltage at
DXP-DXN causes about +1°C error.

A/D Conversion Sequence

If a Start command is written (or generated automatical­ly in the free-running autoconvert mode), the result of
the measurement is available after the end of conver­sion. A BUSY status bit in the status byte shows that the
device is performing a new conversion. The result of the
previous conversion is always available even when the
ADC is busy.

SMBus Serial-Data Input/Output. Open drain.SMBDATA9

SMBus Alert (Interrupt) Output. Open drain.

ALERT

10

Combined Current Source and A/D Positive Input. Do not leave DXP floating. Place a 2200pF capacitor
between DXP and DXN for noise filtering.

DXP5

Supply Voltage Input. Bypass to GND with a 0.1µF capacitor.V

CC

6

Hardware-Standby Input. Temperature and comparison threshold data are retained in standby mode.
Low = standby mode. High = operating mode.

STBY

7

SMBus Serial-Clock InputSMBCLK8

Combined Current Sink and A/D Negative Input. DXN is normally biased to a diode voltage above
ground.

DXN4

GroundGND3

PIN

SMBus Slave Address Select Input. (See Table 6.) ADD0 and ADD1 are sampled upon power-up. Excess
capacitance (>50pF) at the address pins when floating may cause address-recognition problems.

ADD12

SMBus Slave Address Select Input. (See Table 6.) ADD0 and ADD1 are sampled upon power-up. Excess
capacitance (>50pF) at the address pins when floating may cause address-recognition problems.

ADD01

FUNCTIONNAME