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General Description

The MAX1669 fan controller includes a precise digital

thermometer that reports the temperature of a remote

sensor. The remote sensor is a diode-connected transis-

tor—typically a low-cost, easily mounted 2N3906 PNP

type—replacing conventional thermistors or thermocou-

ples. Remote accuracy is ±3°C for transistors from multi-

ple manufacturers, with no calibration needed. The

MAX1669 has an independent fan controller with a low-

current logic output requiring external power compo-

nents to interface to a DC brushless fan. The fan

controller has two modes of operation: a low-frequency

(20Hz to 160Hz) PWM mode intended for driving the fan

motor, or a high-impedance DAC output that generates

a variable DC control voltage. In PWM mode, the FAN

frequency can be synchronized to an external clock.

Other key features include general-purpose inputs/out-

puts (GPIOs) for fan presence detection and a thermo-

stat output intended as a fan override signal in case the

host system loses the ability to communicate. The inter-

nal ADC has a wide input voltage range and gives

overrange readings when too large an input voltage is

applied. Other error-checking includes temperature

out-of-range indication and diode open/short faults.

The MAX1669 is available in a space-saving 16-pin

QSOP package that allows it to fit adjacent to the

SLOT1 connector.

Applications

Pentium

CPU Cooling

Desktop Computers

Notebook Computers

Servers

Workstations

Features

♦ Measures Remote CPU Temperature

♦ No Calibration Required

♦ 20Hz to 160Hz PWM Output for Fan

♦ PWM Frequency Sync Input (260kHz)

♦ Flexible Fan Interface: Linear or PWM

♦ SMBus 2-Wire Serial Interface

♦ Programmable Under/Overtemperature Alarms

♦ ALERT Latched Interrupt Output

♦ OVERT Thermostat Output

♦ Two GPIO Pins

♦ Write-Once Configuration Protection

♦ Supports SMBus Alert Response

♦ ±3°C Temperature Accuracy (-40°C to +125°C,

remote)

♦ 3µA Standby Supply Current

♦ +3V to +5.5V Supply Range

♦ Small 16-Pin QSOP Package

MAX1669

Fan Controller and Remote Temperature Sensor

with SMBus Serial Interface

________________________________________________________________ Maxim Integrated Products 1

I/O1 OVERT

ALERT

SMBDATA

SMBCLK

PGND

FAN

SYNC

TOP VIEW

MAX1669

QSOP

I/O2

ADD0

AGND

ADD1

ADD2

DXN

DXP

19-1574; Rev 0; 1/00

PART

MAX1669EEE

-40°C to +85°C

TEMP. RANGE PIN-PACKAGE

16 QSOP

Pentium is a registered trademark of Intel Corp.

Pin Configuration

Ordering Information

Typical Operating Circuit appears at end of data sheet.

Summary of content (20 pages)

PAGE 1
9-1574; Rev 0; 1/00 Fan Controller and Remote Temperature Sensor with SMBus Serial Interface Features The MAX1669 fan controller includes a precise digital thermometer that reports the temperature of a remote sensor. The remote sensor is a diode-connected transistor—typically a low-cost, easily mounted 2N3906 PNP type—replacing conventional thermistors or thermocouples. Remote accuracy is ±3°C for transistors from multiple manufacturers, with no calibration needed.
PAGE 2
MAX1669 Fan Controller and Remote Temperature Sensor with SMBus Serial Interface ABSOLUTE MAXIMUM RATINGS VCC to AGND...........................................................-0.3V to +6V DXP, ADD_ to AGND.................................-0.3V to (VCC + 0.3V) DXN to AGND.......................................................-0.3V to +0.8V SMBCLK, SMBDATA, ALERT, SYNC, I/O1, I/O2, OVERT, FAN to AGND ......................-0.3V to +6V FAN to PGND ............................................-0.
PAGE 3
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface (VCC = +3.3V, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX UNITS FAN PWM Frequency Error PWM mode, any setting -20 +20 % FAN Total Unadjusted Error DAC mode, any setting, RL = 10kΩ to GND -4 4 %FS FAN Output Voltage High DAC mode, FAN duty factor = 1111b, IOUT = 5mA FAN Output Voltage Low DAC mode, FAN duty factor = 0000b, IOUT = -5mA 2.96 3.
PAGE 4
MAX1669 Fan Controller and Remote Temperature Sensor with SMBus Serial Interface ELECTRICAL CHARACTERISTICS (VCC = +3.3V, TA = -40°C to +85°C, unless otherwise noted.) (Note 5) PARAMETER CONDITIONS MIN MAX UNITS ADC AND POWER SUPPLY Temperature Resolution (Note 1) Monotonicity guaranteed 8 Temperature Error, Remote Diode (Note 2) TR = -55°C to +125°C, diode ideality factor = 1.013 -5 5 °C 3 5.
PAGE 5
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface TEMPERATURE ERROR vs. REMOTE DIODE TEMPERATURE 0 -10 -20 PATH = DXP TO VCC (5V); CONFIG = 02h MAX1669-02 1.0 0.5 0 -0.5 -1.0 14 12 10 6 2 0 -40 -2.0 -2 TEMPERATURE ERROR vs. DXP - DXN CAPACITANCE C = 2200pF 4 3 C = 27nF 2 1 MAX1669-05 -4 -6 -8 -10 -12 -1 -14 100M 1G 100M 7 6 5 4 3 2 0 0 10 FREQUENCY (Hz) 20 30 40 50 3.0 3.5 4.0 4.5 5.0 5.
PAGE 6
Typical Operating Characteristics (continued) (Temperature error = measured - actual, TA = +25°C, unless otherwise noted.) PWM DUTY FACTOR vs. CODE (D3D2D1D0) 4.5 80 MAX1669-10 VCC = +3.3V OR +5V DAC OUTPUT vs. CODE (D3D2D1D0) 5.0 MAX1669-09 100 ILOAD = +10mA TO -10mA VCC = +5V 4.0 DAC OUTPUT (V) DUTY FACTOR (%) MAX1669 Fan Controller and Remote Temperature Sensor with SMBus Serial Interface 60 40 3.5 3.0 2.5 2.0 1.5 20 1.0 0.
PAGE 7
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669 VCC ADDRESS DECODER ADD0 ADD1 ADD2 DXP DXN MUX SMBDATA ADC SMB CONTROL LOGIC SMBCLK GND READ WRITE 8 8 COMMAND-BYTE (INDEX) REGISTER 8 REMOTE-TEMPERATURE DATA REGISTER CONFIGURATION BYTE REGISTER HIGH-TEMPERATURE THRESHOLD STATUS BYTE REGISTER LOW-TEMPERATURE THRESHOLD ALERT RESPONSE ADDRESS REGISTER 8 MAX1669 8 ALERT R DIGITAL COMPARATOR S CONTROL LOGIC Q TEMPERATURE SENSOR I/O1 GENERAL-PURPOSE I/O
PAGE 8
MAX1669 Fan Controller and Remote Temperature Sensor with SMBus Serial Interface The PWM or DAC fan control circuitry is completely independent from the temperature measurement, and software closes the temperature-control feedback loop (Figure 2). ADC and Multiplexer The ADC is an averaging type that integrates over a 62ms period (typ), with excellent noise rejection. The multiplexer automatically steers bias currents through the remote diode, measures the forward voltage, and calculates the temperature.
PAGE 9
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669 Write Byte Format S ADDRESS WR ACK COMMAND ACK DATA ACK P 1 7 bits 1 1 8 bits 1 8 bits 1 1 7-bit slave address: equivalent to chip-select line 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) Read Byte Format S ADDRESS WR ACK COMMAND ACK S ADDRESS RD ACK DATA A P 1
PAGE 10
MAX1669 Fan Controller and Remote Temperature Sensor with SMBus Serial Interface ALERT Interrupts The ALERT interrupt output signal is latched and can only be cleared by reading the Alert Response address. Interrupts are generated in response to THIGH and TLOW comparisons, when there is a fault with the remote diode, or when a high-to-low or low-to-high transition at I/O1 or I/O2 is detected.
PAGE 11
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669 Table 3.
PAGE 12
MAX1669 Fan Controller and Remote Temperature Sensor with SMBus Serial Interface Table 4. Configuration Byte Bit Assignments BIT NAME POR STATE 7 (MSB) MASK0 0 Masks THIGH, TLOW, and diode fault ALERT interrupts when high. If all three MASK_ bits are set high, ALERT interrupts are totally masked. 6 STBY 0 Standby mode control bit. If high, the device immediately stops converting, forces FAN low, and enters standby mode. If low, the device continuously autoconverts at a 2Hz rate.
PAGE 13
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669 Table 6. Fan Duty-Factor Data Byte Bit Assignments (Write Command = 1Bh) BIT NAME FUNCTION NAME FAN duty-factor control bit. D3–D0 are decoded as follows: D3–D0 Duty VOUT (nominal) 0000b 0% 0V 0001b 6.67% 0.0625 · VCC 0010b 13.33% 0.125 · VCC 0011b 20% 0.1875 · VCC 0100b 26.67% 0.25 · VCC 0101b 33.33% 0.3125 · VCC 0110b 40% 0.375 · VCC 0111b 46.67% 0.4375 · VCC 1000b 53.33% 0.5 · VCC 1001b 60% 0.5625 · VCC 1010b 66.67% 0.
PAGE 14
MAX1669 Fan Controller and Remote Temperature Sensor with SMBus Serial Interface Table 7. GPIO Input/Output Data Byte Bit Assignments BIT NAME POR STATE FUNCTION 7 (MSB) DATA1 1 For I/O1 configured as an output (MASK1 bit set high and a pull-up resistor on I/O1), this bit corresponds to the GPIO DATA1 block in Figure 4 and controls the output state of I/O1. To configure I/O1 as an input, set this bit high and clear the MASK1 bit low (Figure 4).
PAGE 15
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669 Table 9. Status Byte Bit Assignments BIT NAME FUNCTION 7 (MSB) I/O1 This bit indicates the current state of I/O1 (unlatched). 6 I/O2 This bit indicates the current state of I/O2 (unlatched). 5 TRAN1* This bit is set if a low-to-high or high-to-low transition has occurred at I/O1 (regardless of the state of the mask bits).
PAGE 16
MAX1669 Fan Controller and Remote Temperature Sensor with SMBus Serial Interface Power-Up Defaults • Interrupt latch is cleared. • ADC begins autoconverting at a 2Hz rate. • Command byte is set to 01h to facilitate quick remote receive-byte queries. • THIGH and TLOW registers are set to +127°C and -55°C limits, respectively. • TCRIT register is set to +100°C. • ALERT and OVERT are reset to high-Z state. • Device is in low-frequency PWM mode, 20Hz setting. • PWM output is off (duty factor set to 0%).
PAGE 17
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface MAX1669 +5V 10k 10k 10k 0.1µF 10k +12V SMBCLK VCC SMBDATA ALERT OVERT 2N3906 DXP 100k 2200pF MAX1669 38k N-CH IRF7201 FAN DXN SYNC ADD0 I/O1 ADD1 I/O2 38k ADD2 AGND PGND SYSTEM POWER GROUND Figure 5. Linear Fan Control (DAC Mode) with Fan “Off” at Power-Up +5V 10k 10k 10k 0.1µF 10k SMBCLK +12V VCC SMBDATA ALERT 22k OVERT 33k P-CH IRF7205 FAN 2N3906 DXP 2200pF 5.
PAGE 18
MAX1669 Fan Controller and Remote Temperature Sensor with SMBus Serial Interface Typical Operating Circuit A B tLOW C D F E G H J I tHIGH K 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 E = SLAVE PULLS SMBDATA LINE LOW F = ACKNOWLEDGE BIT CLOCKED INTO MASTER G = MSB OF DATA CLOCKED INTO MASTER H = LSB OF DATA CLOCKED INTO MASTER tBUF I = ACKNOWLEDGE CLOCK PULS
PAGE 19
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface +3V TO +5.5V 10k 10k 10k 0.
PAGE 20
Fan Controller and Remote Temperature Sensor with SMBus Serial Interface QSOP.EPS MAX1669 Package Information 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.