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±1°C Accurate 8-Channel Temperature Sensor

MAX6581

EVALUATION KIT AVAILABLE

19-5260; Rev 1; 2/13

Ordering Information/Selector Guide

General Description

The MAX6581 precision multichannel temperature

sensor monitors its own temperature and the tempera-

tures of up to seven external diode-connected transis-

tors. All temperature channels have programmable alert

and overtemperature thresholds. When the measured

temperature of a channel crosses the respective thresh-

old, a status bit is set in one of the status registers. Two

open-drain alarm outputs (ALERT and OVERT) assert

corresponding to these bits in the status register(s).

Resistance cancellation is available for all channels and

compensates for high series resistance in circuit-board

traces and thermal diodes.

The 2-wire serial interface accepts SMBus protocols

(write byte, read byte, send byte, and receive byte) for

reading the temperature data and programming the

alarm thresholds.

The MAX6581 is specified for an operating temperature

range of -40NC to +125NC and is available in a 24-pin,

4mm x 4mm thin QFN package with an exposed pad.

Features

S Eight Channels to Measure Seven Remote and

One Local Temperature

S 11-Bit, 0.125NC Resolution

S High Accuracy of ±1NC (max) from +60NC to

+100NC (Remote Channels)

S -64NC to +150NC Remote Temperature Range

S Programmable Undertemperature/

Overtemperature Alerts

S SMBus/I

C-Compatible Interface

S Two Open-Drain Alarm Outputs (ALERT and

OVERT)

S Resistance Cancellation on All Remote Channels

Applications

Desktop Computers

Notebook Computers

Workstations

Servers

Data Communications

Note: All devices are specified over the -40NC to +125NC operating temperature range.

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

**Future product—contact factory for availability.

Typical Application Circuit appears at end of data sheet.

PART SLAVE ADDRESS PIN-PACKAGE

OPERATING

TEMPERATURE RANGE

MEASURED

TEMPERATURE RANGE

MAX6581TG9A+ 0X9A 24 TQFN-EP*

-40NC to +125NC -64NC to +150NC

MAX6581TG9C+** 0X9C 24 TQFN-EP*

-40NC to +125NC -64NC to +150NC

MAX6581TG9E+** 0X9E 24 TQFN-EP*

-40NC to +125NC -64NC to +150NC

MAX6581TG98+** 0X98 24 TQFN-EP*

-40NC to +125NC -64NC to +150NC

For pricing, delivery, and ordering information, please contact Maxim Direct at

1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.

Summary of content (27 pages)

PAGE 1
EVALUATION KIT AVAILABLE MAX6581 ±1°C Accurate 8-Channel Temperature Sensor General Description Features The MAX6581 precision multichannel temperature sensor monitors its own temperature and the temperatures of up to seven external diode-connected transistors. All temperature channels have programmable alert and overtemperature thresholds. When the measured temperature of a channel crosses the respective threshold, a status bit is set in one of the status registers.
PAGE 2
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor ABSOLUTE MAXIMUM RATINGS (All voltages referenced to GND.) VCC, SMBCLK, SMBDATA, ALERT, OVERT, STBY to GND..........................................-0.3V to +4V DXP_ to GND............................................. -0.3V to (VCC + 0.3V) DXN_ to GND............................................ -0.3V to (VCC + 0.3V) SMBDATA, ALERT, OVERT Current................... -1mA to +50mA DXN_ Current....................................................................
PAGE 3
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor ELECTRICAL CHARACTERISTICS (continued) (VCC = +3.0V to +3.6V, TA = -40NC to +125NC, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25NC.
PAGE 4
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor ELECTRICAL CHARACTERISTICS (continued) (VCC = +3.0V to +3.6V, TA = -40NC to +125NC, unless otherwise noted. Typical values are at VCC = +3.3V and TA = +25NC.
PAGE 5
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Typical Operating Characteristics (continued) (VCC = +3.3V, VSTBY = VCC, TA = +25NC, unless otherwise noted.) LOCAL TEMPERATURE ERROR vs. DIE TEMPERATURE 3 REMOTE-DIODE TEMPERATURE ERROR (°C) 4 2 1 0 -1 -2 -3 -4 -5 3 2 1 0 -1 -2 -3 -4 -5 0.001 -10 0 10 20 30 40 50 60 70 80 90 100 0.01 0.1 1 10 DIE TEMPERATURE (°C) POWER-SUPPLY NOISE FREQUENCY (MHz) LOCAL TEMPERATURE ERROR vs. POWER-SUPPLY NOISE FREQUENCY REMOTE-DIODE TEMPERATURE ERROR vs.
PAGE 6
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor VCC OVERT I.C. STBY DXP7 TOP VIEW ALERT Pin Configuration 18 17 16 15 14 13 SMBDATA 19 12 DXN7 SMBCLK 20 11 DXP6 10 DXN6 9 DXN5 8 DXP5 7 DXN4 GND 21 MAX6581 N.C. 22 DXP1 23 *EP 1 2 3 4 5 6 DXP2 DXN2 DXP3 DXN3 DXP4 N.C. DXN1 24 *EP = EXPOSED PAD, CONNECT TO GND Pin Description PIN FUNCTION DXP2 Combined Current Source and ADC Positive Input for Channel 2 Remote Diode.
PAGE 7
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Pin Description (continued) PIN NAME FUNCTION DXN4 Cathode Input for Channel 4 Remote Diode. Connect the cathode of the channel 4 remote-diodeconnected transistor to DXN4. If the channel 4 remote transistor is a substrate pnp (e.g., on a CPU die), connect the base of the pnp to DXN4. Leave DXN4 unconnected or connect to DXP4 if a remote diode is not used. Connect a 100pF capacitor between DXP4 and DXN4 for noise filtering.
PAGE 8
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Pin Description (continued) PIN NAME 21 GND Ground DXP1 Combined Current Source and ADC Positive Input for Channel 1 Remote Diode. Connect DXP1 to the anode of a remote-diode-connected, temperature-sensing transistor. Leave DXP1 unconnected or connect to DXN1 if a remote diode is not used. Connect a 100pF capacitor between DXP1 and DXN1 for noise filtering. 24 DXN1 Cathode Input for Channel 1 Remote Diode.
PAGE 9
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor VCC DXP1 MAX6581 DXN1 DXP2 IRJ ALARM ALU OVERT ALERT DXN2 DXP3 DXN3 DXP4 + REGISTER BANK INPUT BUFFER DXN4 COUNT - COUNTER DXP5 COMMAND BYTE REMOTE TEMPERATURES LOCAL TEMPERATURES ALERT THRESHOLD REF DXN5 OVERT THRESHOLD DXP6 ALERT RESPONSE ADDRESS SMBus INTERFACE DXN6 STBY DXP7 DXN7 LOCAL TRANSISTOR SMBCLK SMBDATA Figure 1.
PAGE 10
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor SMBus Digital Interface 3 is the SMBus write timing diagram and Figure 4 is the SMBus read timing diagram. From a software perspective, the MAX6581 appears as a series of 8-bit registers that contain temperaturemeasurement 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.
PAGE 11
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor A tLOW B C tHIGH D E F G H I J K L M SMBCLK SMBDATA tSU:STA tHD:STA tSU:STO 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 tBUF I = SLAVE PULLS DATA LINE LOW J = ACKNOWLEDGE CLOCKED INTO MASTER K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION M = NEW START CONDITION E = SLAVE PULLS SMBDATA LINE LOW F = ACKNOWLEDGE BIT CLOCKED INTO MASTER G = MSB OF D
PAGE 12
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Table 1.
PAGE 13
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Table 3.
PAGE 14
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Table 3.
PAGE 15
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Diode Fault Detection If a channel’s input DXP_ and DXN_ are left open or are shorted, the MAX6581 detects a diode fault. An open diode fault does not cause either ALERT or OVERT to assert. A bit in the status register for the corresponding channel is set to 1 and the temperature data for the channel is stored as all 1s (FFh). It takes approximately 4ms for the MAX6581 to detect a diode fault.
PAGE 16
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Table 4. Configuration Register (41h) BIT NAME POR VALUE 7 (MSB) STOP 0 Standby-Mode Control Bit. If STOP is set to logic 1, the MAX6581 stops converting and enters standby mode. 6 POR 0 Reset Bit. Set to logic 1 to put the device into its power-on state. This bit is selfclearing. 5 TIMEOUT RESERVED 0 Timeout Enable Bit. Set to logic 0 to enable SMBus timeout. 4 0 Reserved. Must be set to 0. 3 RESERVED 0 Reserved. Must be set to 0.
PAGE 17
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Status Register Functions There are four status registers (see Tables 7–10). The ALERT High Status register indicates whether a measured local or remote temperature has exceeded the associated threshold limit set in an ALERT High Limit register. The OVERT Status register indicates whether a measured temperature has exceeded the associated threshold limit set in an OVERT High Limit register.
PAGE 18
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Table 8. OVERT Status Register (45h) BIT NAME POR STATE 7 (MSB) Remote OVERT 7 0 Channel 7 Remote-Diode Overtemperature Status Bit. This bit is set to logic 1 when the channel 7 remote-diode temperature exceeds the temperature threshold limit in the Remote 7 OVERT High Limit register. 6 Local OVERT 0 Local Channel Overtemperature Status Bit.
PAGE 19
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Table 10. ALERT Low Status Register (47h) BIT NAME POR STATE 7 (MSB) Remote ALERT Low 7 0 Channel 7 Remote-Diode Low-Alert Bit. This bit is set to logic 1 when the channel 7 remote-diode temperature falls below the programmed temperature threshold limit in the Remote 7 ALERT Low Limit register. 6 Local ALERT Low 0 Local Channel Remote-Diode Low-Alert Bit.
PAGE 20
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Table 11. Transistor Ideality Register REGISTER 0x4B B7 B6 B5 B4 B3 B2 B1 B0 IDEALITY FACTOR HEX X X X 0 0 0 0 0 .999 0x00 X X X 0 0 0 0 1 1.000 0x01 X X X 0 0 0 1 0 1.001 0x02 X X X 0 0 0 1 1 1.002 0x03 X X X 0 0 1 0 0 1.003 0x04 X X X 0 0 1 0 1 1.004 0x05 X X X 0 0 1 1 0 1.005 0x06 X X X 0 0 1 1 1 1.006 0x07 X X X 0 1 0 0 0 1.
PAGE 21
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Series-Resistance Cancellation Some thermal diodes on high-power ICs have excessive series resistance that can cause temperature-measurement errors when used with conventional remotetemperature sensors. Channels 1–7 of the MAX6581 have a series-resistance cancellation feature (enabled by bits [7:0] of the Resistance Cancellation register) that eliminates the effect of diode series resistance and interconnection resistance.
PAGE 22
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Offset and Offset Select Registers (4Dh and 4Eh) To compensate for remote temperature reporting errors due to issues with the board layout, the Offset register (4Dh) and Offset Enable register (4Eh) allow for a two’scomplement value to be added to the final ADC conversion output. The Offset register (4Dh) contains the value for the shared temperature offset (i.e., the same offset is applied to all selected remote channels) and has a programmable ±31.
PAGE 23
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Applications Information consistent VBE characteristics. Manufacturers of discrete transistors do not normally specify or guarantee ideality factor. This normally is not a problem since good-quality discrete transistors tend to have ideality factors that fall within a relatively narrow range. Variations in remote temperature readings of less than Q2NC with a variety of discrete transistors have been observed.
PAGE 24
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Thermal Mass and Self-Heating PCB Layout When sensing local temperature, the MAX6581 measures the temperature of the PCB to which it is soldered. The leads provide a good thermal path between the PCB traces and the die. As with all IC temperature sensors, thermal conductivity between the die and the ambient air is poor by comparison, making air-temperature measurements impractical.
PAGE 25
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Twisted-Pair and Shielded Cables connect the twisted-pair cables to DXP_ and DXN_ and the shielded cable to GND. Leave the shielded cable unconnected at the remote sensor. For very long cable runs, the cable’s parasitic capacitance often provides noise filtering; therefore the 100pF capacitor can often be removed or reduced in value. Cable resistance also affects remote-sensor accuracy. For every 1I of series resistance, the error is approximately +0.5NC.
PAGE 26
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Chip Information PROCESS: BiCMOS 26 Package Information For the latest package outline information and land patterns, go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO.
PAGE 27
MAX6581 ±1°C Accurate 8-Channel Temperature Sensor Revision History REVISION NUMBER REVISION DATE 0 8/10 Initial release 1 2/13 Added the Package Thermal Characteristics section; updated Table 1; added 58h register to Table 3; added the Offset and Offset Select Registers (4Dh and 4Eh) section and related bit tables DESCRIPTION PAGES CHANGED — 2, 12, 14, 22 Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product.