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| 19-2138; Rev 3; 8/09 High-Accuracy PWM Output Temperature Sensors General Description The MAX6666/MAX6667 are high-accuracy, low-cost, low-power temperature sensors with a single-wire output. The MAX6666/MAX6667 convert the ambient temperature into a ratiometric PWM output with temperature information contained in the duty cycle of the output square wave. The MAX6666 has a push-pull output and the MAX6667 has an open-drain output. The MAX6666/MAX6667 operate at supply voltages from +3V to +5.5V. The typical unloaded supply current at 5.0V is 200A. Both devices feature a single-wire output that minimizes the number of pins necessary to interface with a microprocessor (P). The output is a square wave with a nominal frequency of 35Hz (20%) at +25C. The output format is decoded as follows: Temperature (C) = 235 - (400 x t1) / t2 Where t1 is fixed with a typical value of 10ms and t2 is modulated by the temperature (Figure 1). The MAX6666/ MAX6667 operate from -40C to +125C and are available in space-saving SOT23 packages. o Simple Single-Wire PWM Output o 1.0C Accuracy at +25C o High Accuracy 1C at TA = +30C 2.5C at TA = +10C to +50C o Operate Up to +125C o Low 200A Typical Current Consumption o Small SOT23 package Features MAX6666/MAX6667 Applications Process Control Industrial HVAC and Environmental Control Automotive P and C Temperature Monitoring PART MAX6666AUT+T MAX6667AUT+T Ordering Information TEMP RANGE -40C to +125C -40C to +125C PINPACKAGE 6 SOT23 6 SOT23 TOP MARK AATF AATG +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. Typical Operating Circuit TOP VIEW t1 t2 Pin Configuration +3.3V VCC + DOUT C INPUT TO TIMER/COUNTER 1 MAX6666 MAX6667 6 I.C. MAX6666 MAX6667 DOUT GND VCC 2 5 I.C. GND 3 4 I.C. SOT23 ________________________________________________________________ Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. High-Accuracy PWM Output Temperature Sensors MAX6666/MAX6667 ABSOLUTE MAXIMUM RATINGS (Voltages Referenced to GND) VCC ........................................................................-0.3V to +6.0V DOUT MAX6666................................................-0.3V to (VCC + 0.3V) MAX6667 ..........................................................-0.3V to + 6.0V DOUT Current ......................................................-1mA to +50mA Continuous Current into Any Other Terminal....................20mA Continuous Power Dissipation (TA = +70C) 6-Pin SOT23 (derate 7.4mW/C above +70C)............595mW Operating Temperature Range .........................-40C to +150C Storage Temperature Range .............................-65C to +150C Junction Temperature ......................................................+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 Supply Voltage Range Supply Current SYMBOL VCC ICC VCC = +3.0V to +5.5V TA = +30C TA = +10C to +50C Temperature Error VCC = +3.3V TA = 0C to +100C TA = -25C to +125C TA = -40C, VCC = +3.3V Nominal t1 Pulse Width MAX6666 Output High Voltage MAX6666 Output Low Voltage MAX6666 Fall Time MAX6666 Rise Time MAX6667 Output Low Voltage MAX6667 Fall Time MAX6667 Output Capacitance MAX6667 Output Leakage Power-Supply Rejection Ratio PSRR VCC = +3.0V to +5.5V IOH = 800A IOL = 800A CL = 100pF, RL = CL = 100pF, RL = ISINK = 1.6mA ISINK = 5.0mA CL = 100pF, RL = 10k CL = 0 40 15 <0.1 0.3 1.0 80 80 0.4 1.2 VCC - 0.4 0.4 -1 -2.5 -3.8 -4.8 -6 10 CONDITIONS MIN 3.0 200 TYP MAX 5.5 500 +1 +2.5 +3.8 +4.8 +6 ms V V ns ns V ns pF A C/V C UNITS V A 2 _______________________________________________________________________________________ High-Accuracy PWM Output Temperature Sensors Typical Operating Characteristics (VCC = +3.3V, TA = +25C, unless otherwise noted.) OUTPUT FREQUENCY vs. TEMPERATURE MAX6666/7 toc01 MAX6666/MAX6667 OUTPUT FREQUENCY vs. SUPPLY VOLTAGE MAX6666/7 toc02 T1 AND T2 TIMES vs. TEMPERATURE 39 TWO TYPICAL PARTS 34 29 T2 24 19 MAX6666/7 toc03 50 45 TEMP = +125C OUTPUT FREQUENCY (Hz) 40 TEMP = +25C OUTPUT FREQUENCY (Hz) 40 30 35 20 30 TIME (ms) 10 25 TEMP = -40C T1 14 9 0 -40 -15 10 35 60 85 110 TEMPERATURE (C) 20 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) -40 -10 20 50 80 110 140 TEMPERATURE (C) OUTPUT ACCURACY vs. TEMPERATURE MAX6666/7 toc04 SUPPLY CURRENT vs. TEMPERATURE MAX6666/7 toc05 SUPPLY CURRENT vs. SUPPLY VOLTAGE 156 SUPPLY CURRENT (A) 154 152 150 148 146 144 142 140 MAX6666/7 toc06 3 2 OUTPUT ACCURACY (C) 1 0 -1 -2 -3 -40 -10 20 50 80 110 TEMPERATURE (C) 210 200 190 SUPPLY CURRENT (A) 180 170 160 150 140 130 120 110 100 -55 -25 5 95 65 TEMPERATURE (C) 35 125 VCC = +3.3V VCC = +5.5V 158 155 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) POWER-SUPPLY REJECTION RATIO vs. TEMPERATURE MAX6666/7 toc07 POWER-SUPPLY REJECTION vs. FREQUENCY MAX6666/7 toc08 0.50 0.45 0.40 0.35 PSRR (C/V) 0.30 0.25 0.20 0.15 0.10 0.05 0 -40 -15 10 35 60 85 110 TEMPERATURE (C) 1.0 CHANGE IN TEMPERATURE (C) 0.5 0 -0.5 VAC = 100mVp-p -1.0 0.01 0.1 1 10 100 1k 10k FREQUENCY (Hz) _______________________________________________________________________________________ 3 High-Accuracy PWM Output Temperature Sensors MAX6666/MAX6667 Typical Operating Characteristics (continued) (VCC = +3.3V, TA = +25C, unless otherwise noted.) MAX6666 OUTPUT RISE AND FALL TIMES vs. CAPACITIVE LOADS MAX6666/7 toc10 MAX6666 OUTPUT FALL TIME MAX6666/7 toc09 1200 1000 800 TIME (ns) 600 400 200 0 CLOAD = 100pF RL = 100k FALL TIME RISE TIME 1V/div 40ns/div 0 300 600 900 1200 1500 CLOAD (pF) OUTPUT LOW VOLTAGE vs. TEMPERATURE MAX6666/7 toc11 OUTPUT HIGH VOLTAGE VS. TEMPERATURE VCC = +3.3V ISOURCE = 800A MAX6666/7 toc12 1.0 0.9 OUTPUT LOW VOLTAGE (V) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -40 -20 0 20 40 60 ISINK = 1mA ISINK = 1.5mA ISINK = 5mA 3.30 3.25 OUTPUT HIGH VOLTAGE (V) 3.20 3.15 3.10 3.05 3.00 80 100 120 140 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (C) TEMPERATURE (C) Pin Description PIN 1 2 3 4, 5, 6 NAME DOUT VCC GND I.C. Supply Voltage Ground Internally Connected. Leave I.C. unconnected or connect to GND. FUNCTION Digital Output Pin. The pulse width of the output waveform is modulated by the temperature. 4 _______________________________________________________________________________________ High-Accuracy PWM Output Temperature Sensors Detailed Description The MAX6666/MAX6667 are high-accuracy, low-cost, low current (200A typ) temperature sensors ideal for interfacing with Cs or Ps. The MAX6666/MAX6667 convert the ambient temperature into a ratiometric PWM output at a nominal frequency of 35Hz (20%) at +25C. The time periods, t1 (high) and t2 (low) (Figure 1), are easily read by the P's timer/counter port. To calculate the temperature, use the expression below: Temperature (C) = +235 - (400 x t1) / t2 The C or P measures the output of the MAX6666/ MAX6667 by counting t 1 and t2 and computing the temperature based on their ratio. The resolution of the count is a function of the processor clock frequency and the resolution of the counter. The MAX6666/ MAX6667 have a resolution of approximately 11 bits. Always use the same clock for t1 and t2 counters so that the temperature is strictly based on a ratio of the two times, thus eliminating errors due to different clocks' frequencies. The MAX6666 (Figure 2a) has a push-pull output and provides rail-to-rail output drive. The ability to source and sink current allows the MAX6666 to drive capacitive loads up to 10nF with less than 1C error. The MAX6667 (Figure 2b) has an open-drain output. The output capacitance should be minimized in MAX6667 applications because the sourcing current is set by the pullup resistor. If the output capacitance becomes too large, lengthy rise and fall times distort the pulse width, resulting in inaccurate measurements. t1 MAX6666/MAX6667 t2 Figure 1. MAX6666/MAX6667 PWM Output Power-Supply Bypassing The MAX6666/MAX6667 operate from a +3V to +5.5V supply. If a noisy power-supply line is used, bypass VCC to GND with a 0.1F capacitor. Power Supply from P Port Pin The low quiescent current of the MAX6666/MAX6667 enables it to be powered from a logic line, which meets the requirements for supply voltage range. This provides a simple shutdown function to totally eliminate quiescent current by taking the logic line low. The logic line must be able to withstand the 0.1F power-supply bypass capacitance. Galvanic Isolation Use an optocoupler to isolate the MAX6666/MAX6667 whenever a high common-mode voltage is present. Because some optocouplers have turn-off times that are much longer than their turn-on times, choose an optocoupler with equal turn-on and turn-off times. Unequal turn-on/turn-off times produce an error in the temperature reading. Applications Information Accurate temperature monitoring requires a good thermal contact between the MAX6666/MAX6667 and the object being monitored. A precise temperature measurement depends on the thermal resistance between the object being monitored and the MAX6666 die. Heat flows in and out of plastic packages primarily through the leads. For the best thermal contact, connect all unused pins to ground. If the sensor is intended to measure the temperature of a heat-generating component on the circuit board, mount the device as close as possible to that component and share the ground traces (if they are not too noisy) with the component. This maximizes the heat transfer from the component to the sensor. Thermal Considerations Self-heating may cause the temperature measurement accuracy of the MAX6666/MAX6667 to degrade in some applications. The quiescent dissipation and the power dissipated by the digital output may cause errors in obtaining the accurate temperature measurement. The temperature errors depend on the thermal conductivity of the package (SOT23, 140C/W), the mounting technique, and the airflow. Static dissipation in the MAX6666/MAX6667 is typically 4.5mW operating at 5V with no load. As a worst-case example, consider the MAX6667 and its maximum rated load of 5mA and assume a maximum output voltage of 0.8V adds 4mW power dissipation. Use Figure 3 to estimate the temperature error. _______________________________________________________________________________________ 5 High-Accuracy PWM Output Temperature Sensors MAX6666/MAX6667 VCC VCC +3.3V P DOUT N N DOUT MAX6667 DOUT GND (a) (b) 2.5V 5.1k TO LOGIC GATE INPUT Figure 2. MAX6666/MAX6667 Output Configuration Figure 4. Low-Voltage Logic MAX6666 TEMPERATURE ERROR vs. LOAD CURRENT 3.5 3.0 TEMPERATURE ERROR (C) MAX 2.5 SO 2.0 1.5 1.0 SOT23-6 0.5 0 0 2 4 6 8 10 LOAD CURRENT (mA) Figure 3. MAX6666 Temperature Error Due to Load Current Low-Voltage Logic Use the MAX6667 open-drain output to drive low-voltage devices. As shown in Figure 4, connect a pullup resistor from the low-voltage logic supply to the MAX6667 output. Limit the resistor's current to about 1mA, thus maintaining an output low logic level of less than 200mV. PROCESS: BiCMOS Chip Information Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 6 SOT23 PACKAGE CODE U6F+6 DOCUMENT NO. 21-0058 6 _______________________________________________________________________________________ High-Accuracy PWM Output Temperature Sensors MAX6666/MAX6667 Revision History REVISION NUMBER 3 REVISION DATE 8/09 DESCRIPTION Updated Ordering Information, Pin Configuration, Absolute Maximum Ratings, and Pin Description sections PAGES CHANGED 1, 2, 4 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 _____________________ 7 (c) 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. |
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