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19-3306; Rev 0; 5/04
2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs
General Description
The MAX6678 monitors its own temperature and the temperatures of two external diode-connected transistors, which typically reside on the die of a CPU or other integrated circuit. The device reports temperature values in digital form using a 2-wire serial interface. The MAX6678 provides a programmable alarm output to generate interrupts, throttle signals, or overtemperature shutdown signals. The 2-wire serial interface accepts standard System Management Bus (SMBus)TM write byte, read byte, send byte, and receive byte commands to read the temperature data and program the alarm thresholds. The temperature data controls a PWM output signal to adjust the speed of a cooling fan, thereby minimizing noise when the system is running cool, but providing maximum cooling when power dissipation increases. Five GPIO pins provide additional flexibility. The GPIO power-up states are set by connecting the GPIO preset inputs to ground or VCC. The MAX6678 is available in a 20-pin QSOP package and a 5mm x 5mm thin QFN package. It operates from 3.0V to 5.5V and consumes just 500A of supply current. Two Thermal-Diode Inputs Local Temperature Sensor Five GPIO Input/Outputs Two PWM Outputs for Fan Drive (Open Drain; May Be Pulled Up to +5V) Programmable Fan-Control Characteristics Automatic Fan Spin-Up Ensures Fan Start Controlled Rate of Change Ensures Unobtrusive Fan-Speed Adjustments 1C Remote Temperature Accuracy (+60C to +145C) Temperature Monitoring Begins at POR for FailSafe System Protection OT Output for Throttling or Shutdown Four Versions Available, Each with a Different Address 5mm x 5mm TQFN Package
Features
MAX6678
Applications
Desktop Computers Notebook Computers Workstations Servers Networking Equipment
SMBus is a trademark of Intel Corp.
PART MAX6678AEP90 MAX6678AEP92 MAX6678AEP94 MAX6678AEP96 MAX6678ATP90
PWMOUT2
PWMOUT1 PRESET3 GPIO0
Ordering Information
TEMP RANGE PINPACKAGE SMBus ADDRESS 1001000 1001001 1001010 1001011 1001000 1001001 1001010 1001011
-40C to +125C 20 QSOP -40C to +125C 20 QSOP -40C to +125C 20 QSOP -40C to +125C 20 QSOP 20 Thin -40C to +125C QFN-EP* -40C to +125C -40C to +125C -40C to +125C 20 Thin QFN-EP* 20 Thin QFN-EP* 20 Thin QFN-EP*
Pin Configurations
VCC
TOP VIEW
MAX6678ATP92 MAX6678ATP94 MAX6678ATP96
20
SMBDATA
19
18
17
16 15 14 OT GPIO1 GPIO2 GPIO3 PRESET0
1 2 3 4 5
*CONNECT EXPOSED PADDLE TO GND
SMBCLK GPIO4 PRESET4 DXP1
MAX6678
13 12 11 10 PRESET1
*EP = Exposed paddle.
6 DXN
7
DXP2
8 GND
9 PRESET2
5mm x 5mm THIN QFN
Pin Configurations continued at end of data sheet.
Typical Operating Circuit appears at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
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2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs MAX6678
ABSOLUTE MAXIMUM RATINGS
VCC to GND ..............................................................-0.3V to +6V OT, SMBDATA, SMBCLK, PWMOUT_, GPIO_ to GND ......................................................-0.3V to +6V DXP_ to GND ..........................................-0.3V to + (VCC + 0.3V) DXN to GND ..........................................................-0.3V to +0.8V PRESET_ to GND ....................................-0.3V to + (VCC + 0.3V) SMBDATA, OT, PWMOUT_ Current....................-1mA to +50mA DXN Current .......................................................................1mA ESD Protection (all pins, Human Body Model) ..................2000V Continuous Power Dissipation (TA = +70C) 20-Pin QSOP (derate 9.1mW/C above +70C).......... 727mW 20-Pin TQFN (derate 34.5mW/C above +70C) .......2759mW Operating Temperature Range .........................-40C to +125C Junction Temperature ......................................................+150C Storage Temperature Range ............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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.
ELECTRICAL CHARACTERISTICS
(VCC = +3.0V to +5.5V, TA = -40C to +125C, unless otherwise noted. Typical values are at VCC = +3.3V, TA = +25C.)
PARAMETER Operating Supply Voltage Range Operating Current SYMBOL VCC IS Interface inactive, ADC active +25C TR +125C, TA = 60C External Temperature Error, VCC = 3.3V VCC = 3.3V 0C TR +145C, +25C TA +100C 0C TR +145C, 0C TA +125C Internal Temperature Error Temperature Resolution Conversion Time PWM Frequency Tolerance Remote-Diode Sourcing Current DXN Source Voltage DIGITAL INPUTS AND OUTPUTS Output Low Voltage (Sink Current) (OT, GPIO_, SMBDATA, PWMOUT_) Output High Leakage Current (OT, GPIO_, SMBDATA, PWMOUT_) Logic-Low Input Voltage (SMBDATA, SMBCLK, PRESET_, GPIO_) Logic-High Input Voltage (SMBDATA, SMBCLK, PRESET_, GPIO_) Input Leakage Current Input Capacitance SMBus TIMING Serial Clock Frequency fSCLK 100 kHz CIN 5 VOL IOH VIL VIH VCC = 3V to 3.6V VCC = 3.6V to 5.5V VCC = 3V to 3.6V VCC = 3.6V to 5.5V 2.1 2.1 1 IOUT = 6mA 0.4 1 0.8 0.8 V A V V A pF (Note 1) High level Low level VCC = +3.3V +25C TR +100C 0C TA +125C 1 8 200 -20 80 8 100 10 0.7 250 300 +20 120 12 CONDITIONS MIN +3.0 0.5 TYP MAX +5.5 1 1 3 4 2.5 4 C C Bits ms % A V C UNITS V mA
2
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2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +3.0V to +5.5V, TA = -40C to +125C, unless otherwise noted. Typical values are at VCC = +3.3V, TA = +25C.)
PARAMETER Clock Low Period Clock High Period Bus Free Time Between Stop and Start Conditions SMBus Start Condition Setup Time Start Condition Hold Time Stop Condition Setup Time Data Setup Time Data Hold Time SMBus Fall Time SMBus Rise Time SMBus Timeout Startup Time After POR SYMBOL tLOW tHIGH tBUF tSU:STA tHD:STO tSU:STO tSU:DAT tHD:DAT tF tR tTIMEOUT tPOR 29 37 90% of SMBCLK to 90% of SMBDATA 10% of SMBDATA to 10% of SMBCLK 90% of SMBCLK to 10% of SMBDATA 10% of SMBDATA to 10% of SMBCLK 10% of SMBCLK to 10% of SMBDATA 10% to 10% 90% to 90% CONDITIONS MIN 4 4.7 4.7 4.7 4 4 250 300 300 1000 55 500 TYP MAX UNITS s s s s s s ns ns ns ns ms ms
MAX6678
Note 1: Deviation from programmed value in Table 6.
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
OPERATING SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX6678 toc02
REMOTE TEMPERATURE ERROR vs. REMOTE-DIODE TEMPERATURE
FAIRCHILD 2N3906
MAX6678 toc03
600
2 1 TEMPERATURE ERROR (C) 0 -1 -2 -3 -4
560 SUPPLY CURRENT (A)
520
480
440
400 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V)
0
25
50
75
100
125
150
TEMPERATURE (C)
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2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs MAX6678
Typical Operating Characteristics (continued)
(TA = +25C, unless otherwise noted.)
LOCAL TEMPERATURE ERROR vs. DIE TEMPERATURE
MAX6678 toc04
REMOTE TEMPERATURE ERROR vs. POWER-SUPPLY NOISE FREQUENCY
MAX6678 toc05
LOCAL TEMPERATURE ERROR vs. POWER-SUPPLY NOISE FREQUENCY
VIN = 250mVP-P SQUARE WAVE APPLIED TO VCC WITH NO BYPASS CAPACITOR
MAX6678 toc06
3 2 TEMPERATURE ERROR (C) 1 0 -1 -2 -3 0 25 50 75 100
2.0 1.5 TEMPERATURE ERROR (C) 1.0 0.5 0 -0.5 -1.0 -1.5
VIN = 250mVP-P SQUARE WAVE APPLIED TO VCC WITH NO BYPASS CAPACITOR
1.0 0.5 TEMPERATURE ERROR (C) 0 -0.5 -1.0 -1.5 -2.0 -2.5
125
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
TEMPERATURE (C)
FREQUENCY (kHz)
FREQUENCY (kHz)
REMOTE TEMPERATURE ERROR vs. COMMON-MODE NOISE FREQUENCY
MAX6678 toc07
REMOTE TEMPERATURE ERROR vs. DIFFERENTIAL NOISE FREQUENCY
0.9 TEMPERATURE ERROR (C) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 VIN = AC-COUPLED TO DXP VIN = 100mVP-P SQUARE WAVE
MAX6678 toc08
TEMPERATURE ERROR vs. DXP-DXN CAPACITANCE
1 TEMPERATURE ERROR (C) 0 -1 -2 -3 -4 -5 -6 TA = +25C
MAX6678 toc09
2.0 1.8 TEMPERATURE ERROR (C) 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0
VIN = AC-COUPLED TO DXP AND DXN VIN = 100mVP-P SQUARE WAVE
1.0
2
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
0.1
1
10
100
FREQUENCY (kHz)
FREQUENCY (kHz)
DXP-DXN CAPACITANCE (nF)
PWMOUT FREQUENCY vs. DIE TEMPERATURE
MAX6678 toc10
PWMOUT FREQUENCY vs. SUPPLY VOLTAGE
MAX6678 toc11
GPIO OUTPUT VOLTAGE vs. GPIO SINK CURRENT
MAX6678 toc12
35
35
500
GPIO OUTPUT VOLTAGE (mV)
PWMOUT FREQUENCY (Hz)
PWMOUT FREQUENCY (Hz)
34
34
400
33
33
300
32
32
200
31
31
100
30 -40 -15 10 60 85 TEMPERATURE (C) 35 110
30 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V)
0 0 5 10 15 20 25 30 35 40 GPIO SINK CURRENT (mA)
4
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2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs
Pin Description
PIN THIN QFN 1 2 3, 12, 13, 14, 16 4, 9, 10, 11, 20 QSOP 3 4 5, 14, 15, 16, 18 2, 6, 11, 12, 13 NAME SMBDATA SMBCLK GPIO0-GPIO4 PRESET0-PRESET4 DESCRIPTION SMBus Serial-Data Input/Output, Open Drain. Can be pulled up to 5.5V, regardless of VCC. Open circuit when VCC = 0. SMBus Serial-Clock Input. Can be pulled up to 5.5V, regardless of VCC. Open circuit when VCC = 0. Active-Low, Open-Drain GPIO Pins. Can be pulled up to 5.5V, regardless of VCC. Open circuit when VCC = 0. GPIO Preset Inputs. Connect to GND or VCC to set POR value of GPIO0-GPIO4. Combined Current Source and A/D Positive Input for Remote Diode. Connect to anode of remote-diode-connected temperature-sensing transistor. Do not leave floating; connect to DXN if no remote diode is used. Place a 2200pF capacitor between DXP_ and DXN for noise filtering. Combined Remote-Diode Cathode Input. Connect cathode of the remote-diodeconnected transistor to DXN. Ground. Connect to a clean ground reference. Active-Low, Open-Drain Over-Temperature Output. Typically used for system shutdown or clock throttling. Can be pulled up to 5.5V regardless of VCC. Open circuit when VCC = 0. Open-Drain Output to Power Transistor Driving Fan. Connect to the gate of a MOSFET or base of a transistor. PWMOUT_ requires a pullup resistor. The pullup resistor can be connected to a supply voltage as high as 5.5V, regardless of the MAX6678's supply voltage. Power-Supply Input. 3.3V nominal. Bypass VCC to GND with 0.1F capacitor.
MAX6678
5, 7
7, 9
DXP1, DXP2
6 8 15
8 10 17
DXN GND OT
17, 19
1, 19
PWMOUT1, PWMOUT2 VCC
18
20
Block Diagram
VCC
Detailed Description
The MAX6678 temperature sensor and fan controller accurately measures the temperature of either two remote pn junctions or one remote pn junction and its own die. The device reports temperature values 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 MAX6678 operates from supply voltages of 3.0V to 5.5V and consumes 500A (typ) of supply current. The temperature data controls a PWM output signal to adjust the speed of a cooling fan. The device also features an overtemperature alarm output to generate interrupts, throttle signals, or shutdown signals. Five GPIO input/outputs provide additional flexibility. The GPIO power-up states are set by connecting the GPIO preset inputs to ground or VCC.
DXP1 DXN DXP2 TEMPERATURE PROCESSING BLOCK PWM GENERATOR BLOCK PWMOUT1 PWMOUT2
OT LOGIC SMBus INTERFACE AND REGISTERS GPIO0 GPIO4 PRESET0 PRESET4 SMBCLK
SMBDATA
MAX6678
GND
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2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs MAX6678
Write Byte Format S -- ADDRESS 7 bits WR -- ACK -- COMMAND 8 bits ACK -- DATA 8 bits ACK -- P 1
Slave address: equivalent to chip-select line of a 3-wire interface Read Byte Format S -- ADDRESS 7 bits WR -- ACK -- COMMAND 8 bits
Command byte: selects which register you are writing to
Data byte: data goes into the register set by the command byte (to set thresholds, configuration masks, and sampling rate) RD -- ACK -- DATA 8 bits /// -- P --
ACK --
S --
ADDRESS 7 bits
Slave address: equivalent to chip-select line Send Byte Format S -- ADDRESS 7 bits WR -- ACK --
Command byte: selects which register you are reading from
Slave address: repeated due to change in dataflow direction Receive Byte Format
Data byte: reads from the register set by the command byte
COMMAND 8 bits
ACK --
P --
S --
ADDRESS 7 bits
RD --
ACK --
DATA 8 bits
/// --
P --
Command byte: sends command with no data, usually used for one-shot command S = Start condition P = Stop condition Shaded = Slave transmission /// = Not acknowledged
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
Figure 1. SMBus Protocols
SMBus Digital Interface
From a software perspective, the MAX6678 appears as a set of byte-wide registers. This device uses a standard SMBus 2-wire/I2CTM-compatible serial interface to access the internal registers. The MAX6678 has four different slave addresses available; therefore, a maximum of four MAX6678 devices can share the same bus. The MAX6678 employs 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 with the shorter protocols in multimaster systems, since a second master could overwrite the command byte without informing the first master. Temperature data can be read from registers 00h and 01h. The temperature data format for these registers is 8 bits, with the LSB representing 1C (Table 1) and the
I2C is a trademark of Philips Corp. Purchase of I2C components from Maxim Integrated Products, Inc., or one of its sublicensed Associated Companies, conveys a license under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips. 6
MSB representing +128C. The MSB is transmitted first. All values below 0C clip to 00h. Table 2 details the register address and function, whether they can be read or written to, and the power-on reset (POR) state. See Tables 2-6 for all other register functions and the Register Descriptions section.
Temperature Reading
The MAX6678 contains two external temperature measurement inputs to measure the die temperature of CPUs or other ICs having on-chip temperature-sensing diodes, or discrete diode-connected transistors as shown in the Typical Operating Circuits. For best accuracy, the discrete diode-connected transistor should be a small-signal device with its collector and base connected together. The on-chip ADC converts the sensed temperature and outputs the temperature data in the format shown in Table 1. Temperature channel 2 can be used to measure either a remote thermal diode or the internal temperature of the MAX6678. Bit D1 of register 02h (Table 2) selects local or remote sensing for temperature channel 2 (1 = local). The temperature measurement resolution is 1C for both local and remote temperatures. The temperature accuracy is within 1C for remote temperature measurements from +60C to +100C.
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2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs MAX6678
A tLOW B tHIGH C D E F G H I J K L M
SMBCLK
SMBDATA
tSU:STA tHD:STA A = START CONDITION B = MSB OF ADDRESS CLOCKED INTO SLAVE C = LSB OF ADDRESS CLOCKED INTO SLAVE D = R/W BIT CLOCKED INTO SLAVE
tSU:DAT 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 I = MASTER PULLS DATA LINE LOW J = ACKNOWLEDGE CLOCKED INTO SLAVE K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION M = NEW START CONDITION
tSU:STO
tBUF
Figure 2. SMBus Write Timing Diagram
A
tLOW
B
tHIGH
C
D
E
F
G
H
I
J
K
L
M
SMBCLK
SMBDATA tSU:STA tHD:STA tSU:DAT tHD:DAT F = ACKNOWLEDGE BIT CLOCKED INTO MASTER G = MSB OF DATA CLOCKED INTO MASTER H = LSB OF DATA CLOCKED INTO MASTER I = MASTER PULLS DATA LINE LOW
tSU:STO tBUF J = ACKNOWLEDGE CLOCKED INTO SLAVE K = ACKNOWLEDGE CLOCK PULSE L = STOP CONDITION M = NEW START CONDITION
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
Figure 3. SMBus Read Timing Diagram
The DXN input is biased at 0.60V above ground by an internal diode to set up the analog-to-digital inputs for a differential measurement. The worst case DXP-DXN differential input voltage range is from 0.25V to 0.95V. Excess resistance in series with the remote diode causes about +0.5C error per ohm. Likewise, a 200V offset voltage forced on DXP-DXN causes about 1C error. High-frequency EMI is best filtered at DXP and DXN with an external 2200pF capacitor. This value can be increased to about 3300pF (max), including cable capacitance. Capacitance higher than 3300pF introduces errors due to the rise time of the switched current source.
Table 1. Temperature Data Byte Format
TEMP (C) 241 240 126 25 0.50 0.00 Diode fault (open) Diode fault (short) ROUNDED TEMP (C) +241 +240 +126 +25 +1 0 -- -- DIGITAL OUTPUT 1111 0001 1111 0000 0111 1110 0001 1001 0000 0001 0000 0000 1110 1111 1111 1111
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2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs MAX6678
PWM Output
1) The PWMOUT_ signals are normally used in one of three ways to control the fan's speed: PWMOUT_ drives the gate of a MOSFET or the base of a bipolar transistor in series with the fan's power supply. The Typical Application Circuit shows the PWMOUT_ driving an n-channel MOSFET. In this case, the PWM invert bit (D4 in register 02h) is set to 1. Figure 4 shows PWMOUT_ driving a p-channel MOSFET and the PWM invert bit must be set to zero. 2) PWMOUT_ is converted (using an external circuit) into a DC voltage that is proportional to duty cycle. This duty-cycle-controlled voltage becomes the power supply for the fan. This approach is less efficient than 1), but can result in quieter fan operation. Figure 5 shows an example of a circuit that converts the PWM signal to a DC voltage. Because this circuit produces a full-scale output voltage when PWMOUT = 0V, bit D4 in register 02h should be set to zero. 3) PWMOUT_ directly drives the logic-level PWM speed-control input on a fan that has this type of input. This approach requires fewer external components and combines the efficiency of 1) with the low noise of 2). An example of PWMOUT_ driving a fan with a speed-control input is shown in Figure 6. Bit D4 in register 02h should be set to 1 when this configuration is used.
PWMOUT 1F 1F +12V
500k
+3.3V 18k 10k
0.01F 120k VOUT TO FAN
0.1F
27k +3.3V
Figure 5. Driving a Fan with a PWM-to-DC Circuit
VCC 5V
4.7k PWMOUT
VCC 5V
Figure 6. Controlling a PWM Input Fan with the MAX6678's PWM Output (Typically, the 35kHz PWM Frequency Is Used)
10k PWMOUT P
Whenever the fan has to start turning from a motionless state, PWMOUT_ is forced high for 2s. After this spin-up period, the PWMOUT_ duty cycle settles to the predetermined value. Whenever spin-up is disabled (bit 2 in the configuration byte = 1) and the fan is off, the duty cycle changes immediately from zero to the nominal value, ignoring the duty-cycle rate-of-change setting. The frequency-select register controls the frequency of the PWM signal. When the PWM signal modulates the power supply of the fan, a low PWM frequency (usually 33Hz) should be used to ensure the circuitry of the brushless DC motor has enough time to operate. When driving a fan with a PWM-to-DC circuit as in Figure 5, the highest available frequency (35kHz) should be used to minimize the size of the filter capacitors. When using a fan with a PWM control input, the frequency normally should be high as well, although some fans have PWM inputs that accept low-frequency drive.
Figure 4. Driving a P-Channel MOSFET for Top-Side PWM Fan Drive
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2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs
The duty cycle of the PWM can be controlled in two ways: 1) Manual PWM control by setting the duty cycle of the fan directly through the fan target duty-cycle registers (0Bh and 0Ch). 2) Automatic PWM control by setting the duty cycle based on temperature. Manual PWM Duty-Cycle Control Clearing the bits that select the temperature channels for fan control (D5 and D4 for PWMOUT1 and D3 and D2 for PWMOUT2) in the fan-configuration register (11h) enables manual fan control. In this mode, the duty cycle written to the fan target duty-cycle register directly controls the corresponding fan. The value is clipped to a maximum of 240. Any value entered above that is changed to 240 automatically. In this control mode, the value in the maximum duty-cycle register is ignored and does not affect the duty cycle used to control the fan. Automatic PWM Duty-Cycle Control In the automatic control mode, the duty cycle is controlled by the local or remote temperature according to the settings in the control registers. Below the fan-start temperature, the duty cycle is either 0% or is equal to the fan-start duty cycle, depending on the value of bit D3 in the configuration byte register. Above the fanstart temperature, the duty cycle increases by one duty cycle step each time the temperature increases by one temperature step. The target duty cycle is calculated based on the following formula; for temperature > FanStartTemperature: DC = FSDC + (T - FST) x where: DC = DutyCycle FSDC = FanStartDutyCycle T = Temperature FST = FanStartTemperature DCSS = DutyCycleStepSize TS = TempStep Duty cycle is recalculated after each temperature conversion if temperature is increasing. If the temperature begins to decrease, the duty cycle is not recalculated until the temperature drops by 5C from the last peak temperature. The duty cycle remains the same until the temperature drops 5C from the last peak temperature or the temperature rises above the last peak temperature. For example, if the temperature goes up to +85C and
DUTY CYCLE REGISTER 02h, BIT D3 = 1 FAN-START DUTY CYCLE TEMP STEP REGISTER 02h, BIT D3 = 0 TEMPERATURE FAN-START TEMPERATURE DUTY-CYCLE STEP SIZE
starts decreasing, duty cycle is not recalculated until the temperature reaches +80C or the temperature rises above +85C. If the temperature decreases further, the duty cycle is not updated until it reaches +75C. For temperature < FanStartTemperature and D2 of configuration register = 0: DutyCycle = 0 For temperature < FanStartTemperature and D2 of configuration register = 1: DutyCycle = FanStartDutyCycle Once the temperature crosses the fan-start temperature threshold, the temperature has to drop below the fan-start temperature threshold minus the hysteresis before the duty cycle returns to either 0% or the fanstart duty cycle. The value of the hysteresis is set by D7 of the fan-configuration register. The duty cycle is limited to the value in the fan maximum duty-cycle register. If the duty-cycle value is larger than the maximum fan duty cycle, it is set to the maximum fan-duty cycle as in the fan maximum duty-cycle register. The temperature step is bit D6 of the fan-configuration register (0Dh). Notice if temperature crosses FanStartTemperature going up with an initial DutyCycle of zero, a spin-up of 2s applies before the duty-cycle calculation controls the value of the fan's duty cycle. FanStartTemperature for a particular channel follows the channel, not the fan. When a fan switches channels, the start temperature also changes to that of the new channel. If DutyCycle is an odd number, it is automatically rounded down to the closest even number.
MAX6678
DCSS TS
Figure 7. Automatic PWM Duty Control
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2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs
Duty-Cycle Rate-of-Change Control To reduce the audibility of changes in fan speed, the rate of change of the duty cycle is limited by the values set in the duty-cycle rate-of-change register. Whenever the target duty cycle is different from the instantaneous duty cycle, the duty cycle increases or decreases at the rate determined by the duty-cycle rate-of-change byte until it reaches the target duty cycle. By setting the rate of change to the appropriate value, the thermal requirements of the system can be balanced against good acoustic performance. Slower rates of change are less noticeable to the user, while faster rates of change can help minimize temperature variations. Remember that the fan controller is part of a complex control system. Because several of the parameters are generally not known, some experimentation may be necessary to arrive at the best settings.
MAX6678
GPIO Inputs/Outputs and Presets
The MAX6678 contains five GPIO pins (GPIO0 through GPIO4). When set as an output, the GPIO pin connects to the drains of internal n-channel MOSFETs. When the n-channel MOSFET is off, the pullup resistor (see the Typical Operating Circuit) provides a logic-level high output. When a GPIO pin is configured as an input, read the state of GPIO_ from the GPIO value register (15h). The MAX6678 powers up with GPIO0, GPIO1, and GPIO2 high impedance and GPIO3 and GPIO4 pulled low. After 2ms, the GPIOs go to their assigned preset values. The preset values are set by connecting the associated PRESET inputs to either GND or VCC. With PRESET"N" connected to GND, GPIO"N" pulls low; with PRESET"N" connected to V CC , GPIO"N" pulls high through the pullup resistor. After power-up, the functions and states of the GPIOs can be read and controlled using registers 15h and 16h.
Power-Up Defaults
At power-up, or when the POR bit in the configuration byte register is set, the MAX6678 has the default settings indicated in Table 2. Some of these settings are summarized below: * Temperature conversions are active. * Channel 1 and channel 2 are set to report the remote temperature channel measurements. * Channel 1 OT limit = +110C. * Channel 2 OT limit = +80C. * Manual fan mode. * Fan duty cycle = 0. * PWM invert bit = 0. * PWMOUT_ are high. * When using an NMOS or npn transistor, the fan starts at full speed on power-up. When temperature exceeds the OT temperature threshold and OT is not masked, the OT status register indicates a fault and OT output becomes active. If OT for the respective channel is masked off, the OT status register continues to be set, but the OT output does not become active. The fault flag and the output can be cleared only by reading the OT status register and the temperature register of that channel. If the OT status bit is cleared, OT reasserts on the next conversion if the temperature still exceeds the OT temperature threshold.
Register Descriptions
The MAX6678 contains 26 internal registers. These registers store temperature, allow control of the PWM outputs, determine if the MAX6678 is measuring from the internal or remote temperature sensors, and set the GPIO as inputs or outputs. Temperature Registers (00h and 01h) These registers contain the results of temperature measurements. The value of the MSB is +128C, and the value of the LSB is +1C. Temperature data for remote diode 1 is in the temperature channel 1 register. Temperature data for remote diode 2 OR the local sensor (selectable by bit D1 in the configuration byte) is stored in the temperature channel 2 register. Configuration Byte (02h) The configuration byte register controls timeout conditions and various PWMOUT signals. The POR state of the configuration byte register is 00h. See Table 3 for configuration byte definitions. Channel 1 and Channel 2 OT Limits (03h and 04h) Set channel 1 (03h) and channel 2 (04h) temperature thresholds with these two registers. Once the temperature is above the threshold, the OT output is asserted low (for the temperature channels that are not masked). The POR state of the channel 1 OT limit register is 6Eh, and the POR state of the channel 2 OT limit register is 50h.
OT Output
10
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2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs MAX6678
Table 2. Register Map
READ/ WRITE REGISTER NO. /ADDRESS 00h POR STATE FUNCTION D7 D6 D5 D4 D3 D2 D1 D0
R
0000 0000
Temperature channel 1 Temperature channel 2
MSB (+128C) MSB (+128C)
--
--
--
--
--
--
LSB (+1C) LSB (+1C)
R
01h
0000 0000
--
--
--
--
--
--
R/W
02h
0001 1000
Configuration byte
Min duty Timeout: cycle: 0 0= PWMOUT PWMOUT Reserved; Reserved; = 0%, enabled, 1 PWM 2 PWM set to 0 set to 0 1 = fan 1= invert invert start duty disabled cycle
Temp channel 2 source: 1 Spin-up = local, 0 disable = remote 2 LSB (+1C)
R/W
03h
0110 1110
Temperature channel 1 OT limit Temperature channel 2 OT limit
MSB
--
--
--
--
--
--
R/W
04h
0101 0000
MSB
--
--
--
--
--
--
LSB (+1C)
R
05h
00xx xxxx
OT status
Channel 1: 1 = fault Channel 1: 1 = masked
Channel 2: 1 = fault Channel 2: 1 = masked --
--
--
--
--
--
--
R/W
06h
00xx xxxx
OT mask
--
--
--
--
--
--
R/W
07h
0110 000x (96 = 40%) 0110 000x (96 = 40%)
PWMOUT1 start MSB duty cycle (128/240) PWMOUT2 start MSB duty cycle (128/240) MSB (128/240) MSB (128/240)
--
--
--
--
LSB (2/240) LSB (2/240) LSB (2/240) LSB (2/240) LSB (2/240) LSB (2/240) LSB (2/240)
--
R/W
08h
--
--
--
--
--
--
R/W R/W
09h 0Ah
1111 000x PWMOUT1 max (240 = 100%) duty cycle 1111 000x PWMOUT2 max (240 = 100%) duty cycle 0000 000x
-- --
-- --
-- --
-- --
-- --
-- --
R/W
0Bh
PWMOUT1 MSB target duty cycle (128/240) PWMOUT2 MSB target duty cycle (128/240) PWMOUT1 instantaneous duty cycle MSB (128/240)
--
--
--
--
--
--
R/W
0Ch
0000 000x
--
--
--
--
--
--
R
0Dh
0000 000x
--
--
--
--
--
--
***GPIO0 through GPIO4 POR values set by Preset0 through Preset4.
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11
2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs MAX6678
Table 2. Register Map (continued)
READ/ WRITE REGISTER NO. /ADDRESS POR STATE FUNCTION D7 D6 D5 D4 D3 D2 D1 D0
R
0Eh
0000 000x
PWMOUT2 instantaneous duty cycle Temperature channel 1 fanstart temperature Temperature channel 2 fanstart temperature
MSB (128/240)
--
--
--
--
--
LSB (2/240)
--
R/W
0Fh
0000 0000
MSB
--
--
--
--
--
--
LSB
R/W
10h
0000 0000
MSB
--
--
--
--
--
--
LSB
R/W
11h
0000 000x
Fan configuration
Temp PWMOUT PWMOUT PWMOUT PWMOUT Hysteresis: step: 0 = 1 control: 1 control: 2 control: 2 control: 0 = 5C, 1C, 1= 1= 1= 1= 1 = 10C 1 = 2C channel1 channel 2 channel 1 channel 2 -- -- PWMOUT PWMOUT 1 LSB 2 MSB -- -- PWMOUT 2 LSB --
--
--
R/W R/W
12h 13h
1011 01xx 0101 0101
Duty-cycle rate PWMOUT of change 1 MSB Duty-cycle step PWMOUT size 1 MSB PWM frequency select Select A
-- --
-- PWMOUT 2 LSB --
PWMOUT PWMOUT 1 LSB 2 MSB -- --
R/W
14h
010x xxxx
Select B
Select C
--
--
R/W
15h
xxx0 0000
GPIO function
--
--
--
GPIO4: 0 GPIO3: 0 GPIO2: 0 GPIO1: 0 GPIO0: 0 = output, = output, = output, = output, = output, 1 = input 1 = input 1 = input 1 = input 1 = input GPIO4 0 GPIO3 0 GPIO2 0 GPIO1 0 GPIO0 1
R/W R
16h FDh
xxx*** 0000 0001
GPIO value Read device revision Read device ID Read manufacturer ID
-- 0
-- 0
-- 0
R
FEh
1000 0110
1
0
0
0
0
1
1
0
R
FFh
0100 1101
0
1
0
0
1
1
0
1
***GPIO0 through GPIO4 POR values set by Preset0 through Preset4.
OT Status (05h) Read the OT status register to determine which channel recorded an overtemperature condition. Bit D7 is high if the fault reading occurred from channel 1. Bit D6 is high if the fault reading occurred in channel 2. The OT status register is cleared only by reading its contents. After reading the OT status register, a temperature register read must be done. Reading the contents of the register also makes the OT output high impedance. If the fault is still present on the next temperature mea12
surement cycle, the corresponding bits and the OT output are set again. The POR state of the OT status register is 00h. OT Mask (06h) Set bit D7 to 1 in the OT mask register to prevent the OT output from asserting on faults in channel 1. Set bit D6 to 1 to prevent the OT output from asserting on faults in channel 2. The POR state of the OT mask register is 00h.
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2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs MAX6678
Table 3. Configuration Byte Definition (02h)
BIT 7 6 5 4 3 NAME Reserved; set to 0 Reserved; set to 0 TIMEOUT FAN1 PWM INVERT FAN2 PWM INVERT POR STATE
-- --
FUNCTION
-- --
0 0 0
Set TIMEOUT to zero to enable SMBus timeout for prevention of bus lockup. Set to 1 to disable this function. Set FAN PWM INVERT to zero to force PWMOUT1 low when the duty cycle is 100%. Set to 1 to force PWMOUT1 high when the duty cycle is 100%. Set FAN PWM INVERT to zero to force PWMOUT2 low when the duty cycle is 100%. Set to 1 to force PWMOUT2 high when the duty cycle is 100%. Set MIN DUTY CYCLE to zero for a 0% duty cycle when the measured temperature is below the fan-temperature threshold in automatic mode. When the temperature equals the fan-temperature threshold, the duty cycle is the value in the fan-start duty-cycle register, and it increases with increasing temperature. Set MIN DUTY CYCLE to 1 to force the PWM duty cycle to the value in the fanstart duty-cycle register when the measured temperature is below the fantemperature threshold. As the temperature increases above the temperature threshold, the duty cycle increases as programmed. Selects either local or remote 2 as the source for temperature channel 2 register data. When D1 = 0, the MAX6678 measures remote 2 and when D1 = 1, the MAX6678 measures the internal die temperature. Set SPIN-UP DISABLE to 1 to disable spin-up. Set to zero for normal fan spin-up.
2
MIN DUTY CYCLE
0
1 0
TEMPERATURE SOURCE SELECT SPIN-UP DISABLE
0 0
PWMOUT Start Duty Cycle (07h and 08h) The PWMOUT start duty-cycle register determines the PWM duty cycle where the fan starts spinning. Bit D2 in the configuration byte register (MIN DUTY CYCLE) determines the starting duty cycle. If the MIN DUTY CYCLE bit is 1, the duty cycle is the value written to the fan-start duty-cycle register at all temperatures below the fan-start temperature. If the MIN DUTY CYCLE bit is zero, the duty cycle is zero below the fan-start temperature and has this value when the fan-start temperature is reached. A value of 240 represents 100% duty cycle. Writing any value greater than 240 causes the fan speed to be set to 100%. The POR state of the fan-start duty-cycle register is 96h, 40%. PWMOUT Max Duty Cycle (09h and 0Ah) The PWMOUT maximum duty-cycle register sets the maximum allowable PWMOUT duty cycle between 2/240 (0.83% duty cycle) and 240/240 (100% duty cycle). Any values greater than 240 are recognized as 100% maximum duty cycle. The POR state of the PWMOUT maximum duty-cycle register is F0h, 100%. In manual control mode, this register is ignored.
PWMOUT Target Duty Cycle (0Bh and 0Ch) In automatic fan-control mode, this register contains the present value of the target PWM duty cycle, as determined by the measured temperature and the dutycycle step size. The actual duty cycle requires time before it equals the target duty cycle if the duty-cycle rate-of-change register is set to a value other than zero. In manual fan-control mode, write the desired value of the PWM duty cycle directly into this register. The POR state of the fan-target duty-cycle register is 00h. PWMOUT1 Instantaneous Duty Cycle, PWMOUT2 Instantaneous Duty Cycle (0Dh, 0Eh) These registers always contain the duty cycle of the PWM signals presented at the PWM output. The POR state of the PWMOUT instantaneous dutycycle register is 00h. Channel 1 and Channel 2 Fan-Start Temperature (0Fh and 10h) These registers contain the temperatures at which fan control begins (in automatic mode). See the Automatic PWM Duty-Cycle Control section for details on setting the fan-start thresholds. The POR state of the channel 1 and channel 2 fan-start temperature registers is 00h.
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13
2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs MAX6678
Table 4. Setting the Time Between DutyCycle Increments
D7:D5, D4:D2 000 001 010 011 100 101 110 111 TIME BETWEEN INCREMENTS (s) 0 0.0625 0.125 0.25 0.5 1 2 4 TIME FROM 33% TO 100% (s) 0 5 10 20 40 80 160 320 0000 0001 0010 0011 0100 0101 ... 1000 ... 1111
Table 5. Setting the Duty-Cycle Change
CHANGE IN DUTY CYCLE PER TEMPERATURE STEP 0 2/240 4/240 6/240 8/240 10/240 ... 16 ... 31 TEMPERATURE RANGE FOR FAN CONTROL (1C STEP, 33% TO 100%) 0 80 40 27 20 16 ... 10 ... 5
D7:D4, D3:D0
Fan Configuration (11h) The fan-configuration register controls the hysteresis level, temperature step size, and whether the remote or local diode controls the PWMOUT2 signal (see Table 2). Set bit D7 of the fan-configuration register to zero to set the hysteresis value to 5C. Set bit D7 to 1 to set the hysteresis value to 10C. Set bit D6 to zero to set the fan-control temperature step size to 1C. Set bit D6 to 1 to set the fan-control temperature step size to +2C. Bits D5 to D2 select which PWMOUT_ channel 1 or channel 2 controls (see Table 2). If both are selected for a given PWMOUT_, the highest PWM value is used. If neither is selected, the fan is controlled by the value written to the fan-target duty-cycle register. Also in this mode, the value written to the target duty-cycle register is not limited by the value in the maximum duty-cycle register. It is, however, clipped to 240 if a value above 240 is written. The POR state of the fan-configuration register is 00h. Duty-Cycle Rate of Change (12h) Bits D7, D6, and D5 (channel 1) and D4, D3, and D2 (channel 2) of the duty-cycle rate-of-change register set the time between increments of the duty cycle. Each increment is 2/240 of the duty cycle (see Table 4). This allows the time from 33% to 100% duty cycle to be adjusted from 5s to 320s. The rate-of-change control is always active in manual mode. To make instant changes, set bits D7, D6, and D5 (channel 1) or D4, D3, and D2 (channel 2) = 000. The POR state of the duty-cycle rate-of-change register is B4h (1s between increments).
Duty-Cycle Step Size (13h) Bits D7-D4 (channel 1) and bits D3-D0 (channel 2) of the duty-cycle step-size register change the size of the dutycycle change for each temperature step. The POR state of the duty-cycle step size register is 55h (see Table 5). PWM Frequency Select (14h) Set bits D7, D6, and D5 (select A, B, and C) in the PWM frequency-select register to control the PWMOUT frequency (see Table 6). The POR state of the PWM frequencyselect register is 40h, 33Hz. The lower frequencies are usually used when driving the fan's power-supply pin as in the Typical Application Circuit, with 33Hz being the most common choice. The 35kHz frequency setting is used for controlling fans that have logic-level PWM input pins for speed control. The minimum duty-cycle resolution is decreased from 2/240 to 4/240 at the 35kHz frequency setting. For example, a result that would return a value of 6/240 is truncated to 4/240.
Table 6. PWM Frequency Select
PWM FREQUENCY (Hz) 20 33 50 100 35k SELECT A 0 0 1 1 X SELECT B 0 1 0 1 X SELECT C 0 0 0 0 1
Note: At 35kHz, duty-cycle resolution is decreased from a resolution of 2/240 to 4/240.
14
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2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs
GPIO Function Register (15h) The GPIO function register (15h) sets the GPIO_ states. Write a zero to set a GPIO as an output. Write a one to set a GPIO as an input. GPIO Value Register (16h) The GPIO value register (16h) contains the state of each GPIO input when a GPIO is configured as an input. When configured as an output, write a one or zero to set the value of the GPIO output. As an example, assume the MAX6678 is configured with a CPU that has an ideality factor of 1.002. If the diode has no series resistance, the measured data is related to the real temperature as follows:
n 1.008 TACTUAL = TM NOMINAL = TM = TM (1.00599) 1.002 n1
MAX6678
Applications Information
Remote-Diode Considerations
Temperature accuracy depends upon having a goodquality, diode-connected, small-signal transistor. Accuracy has been experimentally verified for all the devices listed in Table 7. The MAX6678 can also directly measure the die temperature of CPUs and other ICs with on-board temperature-sensing diodes. The transistor must be a small-signal type with a relatively high forward voltage. This ensures that the input voltage is within the A/D input voltage range. The forward voltage must be greater than 0.25V at 10A at the highest expected temperature. The forward voltage must be less than 0.95V at 100A at the lowest expected temperature. The base resistance has to be less than 100. Tight specification of forward-current gain (+50 to +150, for example) indicates that the manufacturer has good process control and that the devices have consistent characteristics.
For a real temperature of +85C (358.15K), the measured temperature is +82.87C (356.02K), which is an error of -2.13C.
Effect of Series Resistance
Series resistance in a sense diode contributes additional errors. For nominal diode currents of 10A and 100A, change in the measured voltage is: VM = RS (100A - 10A) = 90A x RS Since 1C corresponds to 198.6V, series resistance contributes a temperature offset of: = 0.453 C V 198.6 C Assume that the diode being measured has a series resistance of 3. The series resistance contributes an offset of: 3 x 0.453 C = 1.36C 90 V
Effect of Ideality Factor
The accuracy of the remote-temperature measurements depends on the ideality factor (n) of the remote "diode" (actually a transistor). The MAX6678 is optimized for n = 1.008, which is the typical value for the Intel Pentium(R) III and the AMD AthlonTM MP model 6. If a sense transistor with a different ideality factor is used, the output data is different. Fortunately, the difference is predictable. Assume a remote-diode sensor designed for a nominal ideality factor nNOMINAL is used to measure the temperature of a diode with a different ideality factor, n1. The measured temperature TM can be corrected using: n1 TM = TACTUAL nNOMINAL where temperature is measured in Kelvin. As mentioned above, the nominal ideality factor of the MAX6678 is 1.008.
Pentium is a registered trademark of Intel Corp. Athlon is a trademark of AMD.
The effects of the ideality factor and series resistance are additive. If the diode has an ideality factor of 1.002 and series resistance of 3, the total offset can be calculated by adding error due to series resistance with error due to ideality factor: 1.36C - 2.13C = -0.77C for a diode temperature of +85C. In this example, the effect of the series resistance and the ideality factor partially cancel each other. For best accuracy, the discrete transistor should be a small-signal device with its collector connected to GND and base connected to DXN. Table 7 lists examples of discrete transistors that are appropriate for use with the MAX6678.
______________________________________________________________________________________
15
2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs MAX6678
ADC Noise Filtering
The integrating ADC has inherently good noise rejection, especially of low-frequency signals such as 60Hz/120Hz power-supply hum. Micropower operation places constraints on high-frequency noise rejection. Lay out the PC board carefully with proper external noise filtering for high-accuracy remote measurements in electrically noisy environments. Filter high-frequency electromagnetic interference (EMI) at DXP and DXN with an external 2200pF capacitor connected between the two inputs. This capacitor can be increased to about 3300pF (max), including cable capacitance. A capacitance higher than 3300pF introduces errors due to the rise time of the switchedcurrent source.
Table 7. Remote-Sensor Transistor Manufacturers
MANUFACTURER Central Semiconductor (USA) Rohm Semiconductor (USA) Samsung (Korea) Siemens (Germany) MODEL NO. CMPT3906 SST3906 KST3906-TF SMBT3906
3) Route the DXP and DXN traces parallel and close to each other, away from any high-voltage traces such as +12VDC. Avoid leakage currents from PC board contamination. A 20M leakage path from DXP ground causes approximately +1C error. 4) Connect guard traces to GND on either side of the DXP/DXN traces. With guard traces, placing routing near high-voltage traces is no longer an issue. 5) Route as few vias and crossunders as possible to minimize copper/solder thermocouple effects. 6) When introducing a thermocouple, make sure that both the DXP and the DXN paths have matching thermocouples. In general, PC board-induced thermocouples are not a serious problem. A copper solder thermocouple exhibits 3V/C, and it takes approximately 200V of voltage error at DXP/DXN to cause a +1C measurement error, so most parasitic thermocouple errors are swamped out. 7) Use wide traces. Narrow traces are more inductive and tend to pick up radiated noise. The 10-mil widths and spacings recommended are not absolutely necessary (as they offer only a minor improvement in leakage and noise), but use them where practical. 8) Placing an electrically clean copper ground plane between the DXP/DXN traces and traces carrying high-frequency noise signals helps reduce EMI.
Twisted Pairs and Shielded Cables
For remote-sensor distances longer than 8in, or in particularly noisy environments, a twisted pair is recommended. Its practical length is 6ft to 12ft (typ) before noise becomes a problem, as tested in a noisy electronics laboratory. For longer distances, the best solution is a shielded twisted pair like that used for audio microphones. For example, Belden 8451 works well for distances up to 100ft in a noisy environment. Connect the twisted pair to DXP and DXN and the shield to ground, and leave the shield's remote end unterminated. Excess capacitance at DXN or DXP limits practical remote-sensor distances (see the Typical Operating Characteristics). For very long cable runs, the cable's parasitic capacitance often provides noise filtering, so the recommended 2200pF capacitor can often be removed or reduced in value. Cable resistance also affects remote-sensor accuracy. A 1 series resistance introduces about +1/2C error.
PC Board Layout Checklist
1) Place the MAX6678 as close as practical to the remote diode. In a noisy environment, such as a computer motherboard, this distance can be 4in to 8in, or more, as long as the worst noise sources (such as CRTs, clock generators, memory buses, and ISA/PCI buses) are avoided. 2) Do not route the DXP/DXN lines next to the deflection coils of a CRT. Also, do not route the traces across a fast memory bus, which can easily introduce +30C error, even with good filtering. Otherwise, most noise sources are fairly benign.
16
______________________________________________________________________________________
2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs
Typical Application Circuit
VFAN (5V OR 12V) 5.0V 3.0V TO 5.5V CPU VCC DXP1 PWMOUT1 5V REMOTE 1 DXN
MAX6678
VFAN (5V OR 12V)
DXP2
PWMOUT2 3.0V TO 5.5V
MAX6678
OT REMOTE 2 GPU 3.0V TO 5.5V TO SMBus MASTER SMBCLK 3.0V TO 5.5V GPIO3 GPIO1 GPIO0 3.0V TO 5.5V SMBDATA 3.0V TO 5.5V 3.0V TO 5.5V TO CLOCK THROTTLE OR SYSTEM SHUTDOWN
GPIO4 GND
GPIO2 PRESET_ 5
Pin Configurations (continued)
TOP VIEW
PWMOUT2 1 PRESET3 2 SMBDATA 3 SMBCLK 4 GPIO4 5 PRESET4 6 DXP1 7 DXN 8 DXP2 9 GND 10 20 VCC 19 PWMOUT1 18 GPIO0 17 OT
Chip Information
TRANSISTOR COUNT: 23,618 PROCESS: BiCMOS
MAX6678
16 GPIO1 15 GPIO2 14 GPIO3 13 PRESET0 12 PRESET1 11 PRESET2
QSOP
______________________________________________________________________________________
17
2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs MAX6678
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE, QSOP .150", .025" LEAD PITCH
21-0055
E
1
1
18
______________________________________________________________________________________
QSOP.EPS
2-Channel Temperature Monitor with Dual Automatic PWM Fan-Speed Controller and Five GPIOs
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.)
QFN THIN.EPS
MAX6678
0.15 C A
D2
C L
D
b D2/2
0.10 M C A B
PIN # 1 I.D.
D/2
0.15 C B
k
PIN # 1 I.D. 0.35x45
E/2 E2/2 E (NE-1) X e
C L
E2
k L
DETAIL A
e (ND-1) X e
DETAIL B
e
L1
L
C L
C L
L
L
e 0.10 C A 0.08 C
e
C
A1
A3 PACKAGE OUTLINE 16, 20, 28, 32, 40L, THIN QFN, 5x5x0.8mm
21-0140
E
1
2
COMMON DIMENSIONS PKG. 20L 5x5 28L 5x5 32L 5x5 40L 5x5 16L 5x5 SYMBOL MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. MIN. NOM. MAX. A A1 A3 b D E e k L L1 N ND NE JEDEC 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0.70 0.75 0.80 0 0.02 0.05 0.20 REF. 0 0.02 0.05 0.20 REF. 0 0.02 0.05 0.20 REF. 0 0.02 0.05 0.20 REF. 0 0.05 0.20 REF. PKG. CODES T1655-1 T1655-2 T2055-2 T2055-3 T2055-4 T2855-1 T2855-2 T2855-3 T2855-4 T2855-5 T2855-6 T2855-7 T3255-2 T3255-3 T3255-4 T4055-1
EXPOSED PAD VARIATIONS
D2
MIN. NOM. MAX. MIN.
E2 3.10 3.20 3.10 3.20 3.10 3.20 3.10 3.20 3.10 3.25 2.70 3.25 2.70 2.70 3.25 2.70 3.10 3.10 3.10 3.20 3.35 2.80 3.35 2.80 2.80 3.35 2.80 3.20 3.20 3.20
NOM. MAX. ALLOWED
DOWN BONDS
3.00 3.00 3.00 3.00 3.00 3.15 2.60 3.15 2.60 2.60 3.15 2.60 3.00 3.00 3.00 3.20
3.10 3.20 3.00 3.10 3.20 3.00 3.10 3.20 3.00 3.10 3.20 3.00 3.10 3.25 2.70 3.25 2.70 2.70 3.25 2.70 3.10 3.10 3.10 3.20 3.35 2.80 3.35 2.80 2.80 3.35 2.80 3.20 3.20 3.20 3.00 3.15 2.60 3.15 2.60 2.60 3.15 2.60 3.00 3.00 3.00
0.25 0.30 0.35 0.25 0.30 0.35 0.20 0.25 0.30 0.20 0.25 0.30 0.15 0.20 0.25 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 4.90 5.00 5.10 0.80 BSC. 0.65 BSC. 0.50 BSC. 0.50 BSC. 0.40 BSC. - 0.25 - 0.25 - 0.25 0.35 0.45 0.25 - 0.25 0.30 0.40 0.50 0.45 0.55 0.65 0.45 0.55 0.65 0.30 0.40 0.50 0.40 0.50 0.60 16 4 4 WHHB 20 5 5 WHHC 28 7 7 WHHD-1 32 8 8 WHHD-2 0.30 0.40 0.50 40 10 10 -
NO YES NO YES NO NO NO YES YES NO NO YES NO YES NO YES
3.30 3.40 3.20
3.30 3.40
NOTES: 1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994. 2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES. 3. N IS THE TOTAL NUMBER OF TERMINALS. 4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE. 5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm FROM TERMINAL TIP. 6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY. 7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION. 8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS. 9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT EXPOSED PAD DIMENSION FOR T2855-1, T2855-3 AND T2855-6. 10. WARPAGE SHALL NOT EXCEED 0.10 mm.
PACKAGE OUTLINE 16, 20, 28, 32, 40L, THIN QFN, 5x5x0.8mm
21-0140
E
2
2
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 19 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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