19-2138; Rev 3; 8/09 High-Accuracy PWM Output Temperature Sensors 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 200µA. Both devices feature a single-wire output that minimizes the number of pins necessary to interface with a microprocessor (µP). The output is a square wave with a nominal frequency of 35Hz (±20%) at +25°C. The output format is decoded as follows: Temperature (°C) = 235 - (400 x t1) / t2 Features o Simple Single-Wire PWM Output o ±1.0°C Accuracy at +25°C o High Accuracy ±1°C at TA = +30°C ±2.5°C at TA = +10°C to +50°C o Operate Up to +125°C o Low 200µA Typical Current Consumption o Small SOT23 package Where t1 is fixed with a typical value of 10ms and t2 is modulated by the temperature (Figure 1). The MAX6666/ MAX6667 operate from -40°C to +125°C and are available in space-saving SOT23 packages. Applications Ordering Information Process Control PINPACKAGE TOP MARK PART TEMP RANGE HVAC and Environmental Control MAX6666AUT+T -40°C to +125°C 6 SOT23 AATF Automotive MAX6667AUT+T -40°C to +125°C 6 SOT23 AATG Industrial +Denotes a lead(Pb)-free/RoHS-compliant package. T = Tape and reel. µP and µC Temperature Monitoring Pin Configuration Typical Operating Circuit TOP VIEW +3.3V t1 VCC + DOUT t2 µC MAX6666 MAX6667 DOUT GND INPUT TO TIMER/COUNTER 1 VCC 2 MAX6666 MAX6667 GND 3 6 I.C. 5 I.C. 4 I.C. SOT23 ________________________________________________________________ Maxim Integrated Products 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. 1 MAX6666/MAX6667 General Description MAX6666/MAX6667 High-Accuracy PWM Output Temperature Sensors 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 = +70°C) 6-Pin SOT23 (derate 7.4mW/°C above +70°C)............595mW Operating Temperature Range .........................-40°C to +150°C Storage Temperature Range .............................-65°C to +150°C Junction Temperature ......................................................+150°C Lead Temperature (soldering,10s) ..................................+300°C 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 = -40°C to +125°C, unless otherwise noted. Typical values are at VCC = +3.3V, TA = +25°C.) PARAMETER SYMBOL Supply Voltage Range VCC Supply Current ICC CONDITIONS TYP 3.0 VCC = +3.0V to +5.5V TA = +30°C TA = +10°C to +50°C Temperature Error MIN VCC = +3.3V 200 MAX UNITS 5.5 V 500 µA -1 +1 -2.5 +2.5 TA = 0°C to +100°C -3.8 +3.8 TA = -25°C to +125°C -4.8 +4.8 -6 +6 TA = -40°C, VCC = +3.3V Nominal t1 Pulse Width 10 MAX6666 Output High Voltage IOH = 800µA MAX6666 Output Low Voltage IOL = 800µA ms VCC - 0.4 V 0.4 MAX6666 Fall Time CL = 100pF, RL = ∞ 80 MAX6666 Rise Time CL = 100pF, RL = ∞ 80 MAX6667 Output Low Voltage °C V ns ns ISINK = 1.6mA 0.4 ISINK = 5.0mA 1.2 V MAX6667 Fall Time CL = 100pF, RL = 10kΩ 40 ns MAX6667 Output Capacitance CL = 0 15 pF MAX6667 Output Leakage Power-Supply Rejection Ratio 2 <0.1 PSRR VCC = +3.0V to +5.5V 0.3 _______________________________________________________________________________________ µA 1.0 °C/V High-Accuracy PWM Output Temperature Sensors 20 30 T2 24 T1 TEMP = -40°C 14 9 20 10 35 60 85 110 3.0 4.5 5.0 SUPPLY VOLTAGE (V) OUTPUT ACCURACY vs. TEMPERATURE SUPPLY CURRENT vs. TEMPERATURE SUPPLY CURRENT (µA) 0 -1 130 120 -3 110 100 50 80 VCC = +3.3V 140 -2 110 80 110 140 158 156 154 152 150 148 146 144 142 140 -55 -25 TEMPERATURE (°C) 5 35 95 65 TEMPERATURE (°C) POWER-SUPPLY REJECTION RATIO vs. TEMPERATURE 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 125 155 3.0 3.5 4.0 4.5 5.0 5.5 SUPPLY VOLTAGE (V) POWER-SUPPLY REJECTION vs. FREQUENCY MAX6666/7 toc07 0.50 PSRR (°C/V) 50 1.0 MAX6666/7 toc08 20 VCC = +5.5V 160 150 20 SUPPLY CURRENT vs. SUPPLY VOLTAGE 180 170 -10 TEMPERATURE (°C) 190 1 -40 5.5 210 200 MAX6666/7 toc04 2 -10 4.0 TEMPERATURE (°C) 3 -40 3.5 MAX6666/7 toc05 -15 CHANGE IN TEMPERATURE (°C) -40 SUPPLY CURRENT (µA) 0 MAX6666/7 toc03 29 19 25 10 OUTPUT ACCURACY (°C) TEMP = +25°C 35 TWO TYPICAL PARTS 34 MAX6666/7 toc06 30 40 39 TIME (ms) OUTPUT FREQUENCY (Hz) 40 TEMP = +125°C MAX6666/7 toc02 45 MAX6666/7 toc01 OUTPUT FREQUENCY (Hz) 50 T1 AND T2 TIMES vs. TEMPERATURE OUTPUT FREQUENCY vs. SUPPLY VOLTAGE OUTPUT FREQUENCY vs. TEMPERATURE 0.5 0 -0.5 0.05 VAC = 100mVp-p 0 -1.0 -40 -15 10 35 60 TEMPERATURE (°C) 85 110 0.01 0.1 1 10 100 1k 10k FREQUENCY (Hz) _______________________________________________________________________________________ 3 MAX6666/MAX6667 Typical Operating Characteristics (VCC = +3.3V, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC = +3.3V, TA = +25°C, unless otherwise noted.) MAX6666 OUTPUT RISE AND FALL TIMES vs. CAPACITIVE LOADS MAX6666 OUTPUT FALL TIME MAX6666/7 toc09 1000 FALL TIME 800 TIME (ns) 1V/div MAX6666/7 toc10 1200 CLOAD = 100pF RL = 100kΩ RISE TIME 600 400 200 0 0 40ns/div 300 600 900 1200 1500 CLOAD (pF) OUTPUT LOW VOLTAGE vs. TEMPERATURE 0.6 0.5 0.4 ISINK = 1.5mA 0.3 0.2 ISINK = 1mA 0.1 0 3.25 MAX6666/7 toc12 ISINK = 5mA 0.7 3.30 OUTPUT HIGH VOLTAGE (V) 0.9 0.8 OUTPUT HIGH VOLTAGE VS. TEMPERATURE MAX6666/7 toc11 1.0 OUTPUT LOW VOLTAGE (V) MAX6666/MAX6667 High-Accuracy PWM Output Temperature Sensors VCC = +3.3V ISOURCE = 800µA 3.20 3.15 3.10 3.05 3.00 -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) -40 -20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) Pin Description 4 PIN NAME FUNCTION 1 DOUT 2 VCC Supply Voltage 3 GND Ground 4, 5, 6 I.C. Digital Output Pin. The pulse width of the output waveform is modulated by the temperature. Internally Connected. Leave I.C. unconnected or connect to GND. _______________________________________________________________________________________ High-Accuracy PWM Output Temperature Sensors The MAX6666/MAX6667 are high-accuracy, low-cost, low current (200µA typ) temperature sensors ideal for interfacing with µCs or µPs. The MAX6666/MAX6667 convert the ambient temperature into a ratiometric PWM output at a nominal frequency of 35Hz (±20%) at +25°C. The time periods, t1 (high) and t2 (low) (Figure 1), are easily read by the µP’s timer/counter port. To calculate the temperature, use the expression below: Temperature (°C) = +235 - (400 x t1) / t2 The µC or µP 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 1°C 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. 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. t1 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 0.1µF capacitor. Power Supply from µP 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 0.1µF 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. 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, 140°C/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 MAX6666/MAX6667 Detailed Description VCC VCC +3.3V 2.5V P DOUT DOUT 5.1kΩ MAX6667 N N DOUT TO LOGIC GATE INPUT GND (a) (b) Figure 2. MAX6666/MAX6667 Output Configuration Figure 4. Low-Voltage Logic MAX6666 TEMPERATURE ERROR vs. LOAD CURRENT 3.5 3.0 TEMPERATURE ERROR (°C) MAX6666/MAX6667 High-Accuracy PWM Output Temperature Sensors µMAX 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 Chip Information 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 Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. 6 PACKAGE TYPE PACKAGE CODE DOCUMENT NO. 6 SOT23 U6F+6 21-0058 _______________________________________________________________________________________ High-Accuracy PWM Output Temperature Sensors REVISION NUMBER REVISION DATE 3 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 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX6666/MAX6667 Revision History