19-2660; Rev 1; 1/03 Low-Voltage, 1.8kHz PWM Output Temperature Sensors Where t1 is fixed with a typical value of 0.24ms and t2 is modulated by the temperature. The MAX6676/ MAX6677 operate from -40°C to +125°C and are available in space-saving 6-pin SOT23 packages. Features ♦ Simple Single-Wire, 1.8kHz PWM Output ♦ Operates Down to 1.8V ♦ High Accuracy ±1.5°C at TA = +25°C ±3.0°C at TA = 0°C to +85°C ♦ Operates from -40°C to +125°C ♦ Low 80µA Typical Current Consumption ♦ Small 6-Pin SOT23 Package Ordering Information TEMP RANGE PINPACKAGE MAX6676AUT3-T -40°C to +125°C 6 SOT23-6 MAX6676AUT5-T -40°C to +125°C 6 SOT23-6 MAX6677AUT3-T -40°C to +125°C 6 SOT23-6 PART Applications Selector Guide Process Control OUTPUT TYPE SUPPLY VOLTAGE RANGE (V) TOP MARK MAX6676AUT3 Open drain 1.8 to 3.6 ABBF MAX6676AUT5 Open drain 3.6 to 5.5 ABBG MAX6677AUT3 Push-pull 1.8 to 3.6 ABBH PART Industrial HVAC and Environmental Control Automotive Portable Devices µP and µC Temperature Monitoring Isolated Temperature Sensing Pin Configuration Typical Operating Circuit VCC TOP VIEW 5.1kΩ* VCC DOUT 1 INPUT TO TIMER/COUNTER DOUT 0.1µF t2 MAX6676 µC GND 2 MAX6676 MAX6677 6 GND 5 GND 4 GND t1 GND VCC 3 SOT23 *REQUIRED ONLY FOR MAX6676. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX6676/MAX6677 General Description The MAX6676/MAX6677 are high-accuracy, low-power temperature sensors with a single-wire output. The MAX6676/MAX6677 convert the ambient temperature into a ratiometric PWM output with temperature information contained in the duty cycle of the output square wave. The MAX6676 has an open-drain output and the MAX6677 has a push-pull output. The MAX6676/MAX6677 are specified for operation with power-supply voltages from 1.8V to 3.6V, or from 3.6V to 5.5V (MAX6676 only). The typical unloaded supply current is 80µA. All 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 1.8kHz (±20%) at +25°C. The output format is decoded as follows: Temperature (°C) = 398.15 ✕ (t1 / t2) - 273.15 MAX6676/MAX6677 Low-Voltage, 1.8kHz PWM Output Temperature Sensors ABSOLUTE MAXIMUM RATINGS (Voltages Referenced to GND) VCC ........................................................................-0.3V to +6.0V DOUT (MAX6676)..................................................-0.3V to +6.0V DOUT (MAX6677).......................................-0.3V to (VCC + 0.3V) DOUT Current .....................................................-1mA to +50mA ESD Protection (DOUT, Human Body Model) .................±2000V Continuous Power Dissipation (TA = +70°C) 6-Pin SOT23 (derate 8.7mW/°C above +70°C).........695.7mW Operating Temperature Range .........................-40°C to +125°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 = 1.8V to 3.6V (MAX6676AUT3/MAX6677AUT3), VCC = 3.6V to 5.5V (MAX6676AUT5), TA = -40°C to +125°C, unless otherwise noted. Typical values are at VCC = 3.0V (MAX6676AUT3/MAX6677AUT3), VCC = 5.0V (MAX6676AUT5), TA = +25°C.) PARAMETER SYMBOL Supply Voltage Range VCC Supply Current ICC Temperature Error CONDITIONS MIN 1.8 3.6 MAX6676AUT5 3.6 5.5 RL = ∞ 80 -1.5 +1.5 TA = 0°C to +85°C -3.0 +3.0 TA = -20°C to +100°C -4.2 +4.2 TA = -40°C to +125°C -5.5 VOH IOH = 800µA, MAX6677 VOL IOL = 3mA tF Rise Time tR Digital Output Capacitance COUT Power-Supply Rejection Ratio PSRR °C µA 0.3 20 300 MAX6677, CL = 100pF, RL = 10kΩ 30 +0.4 Note 1: Parts are tested at +25°C. Specifications are guaranteed by design over temperature. _______________________________________________________________________________________ V ns ns 15 -1.2 µA V MAX6676, CL = 15pF, RL = 10kΩ VCC = 1.8V - 3.6V V µs 0.1 CL = 100pF, RL = 10kΩ UNITS +5.5 VCC 0.3 VOUT = VCC Fall Time 2 200 TA = +25°C 240 Output Leakage Current Output Low Voltage MAX MAX6676AUT3/MAX6677AUT3 Nominal t1 Pulse Width Output High Voltage TYP pF +1.2 °C/V Low-Voltage, 1.8kHz PWM Output Temperature Sensors OUTPUT FREQUENCY vs. TEMPERATURE 2.0 1.5 TEMP = +125°C 2.00 10 35 60 85 110 2.1 2.7 3.0 3.3 -40 3.6 10 35 60 85 110 OUTPUT ACCURACY vs. TEMPERATURE MAX6676AUT3 SUPPLY CURRENT vs. TEMPERATURE MAX6676AUT3 SUPPLY CURRENT vs. SUPPLY VOLTAGE VCC = 3.6V 400 300 VCC = 3.0V 200 400 SUPPLY CURRENT (µA) 500 SUPPLY CURRENT (µA) -1 450 VCC = 1.8V MAX6676 toc06 600 MAX6676 toc04 1 350 300 250 5.1kΩ PULLUP 200 150 100 100 -5 0 0 10 35 60 85 110 NO PULLUP 50 5.1kΩ PULLUP RESISTOR -15 -15 TEMPERATURE (°C) 3 -40 -15 10 35 60 85 1.8 110 2.1 2.4 2.7 3.0 3.3 TEMPERATURE (°C) TEMPERATURE (°C) SUPPLY VOLTAGE (V) POWER-SUPPLY REJECTION RATIO vs. TEMPERATURE POWER-SUPPLY REJECTION RATIO vs. FREQUENCY OUTPUT FALL TIME (CL = 100pF, RL = 100kΩ) 0.5 0 -0.5 2 1 3.6 MAX6676 toc09 MAX6676 toc08 MAX6676 toc07 1.0 CHANGE IN TEMPERATURE (°C) -40 MAX6676 toc03 200 2.4 SUPPLY VOLTAGE (V) -3 PSRR (°C/V) t1 TEMPERATURE (°C) 5 OUTPUT ACCURACY (°C) 1.8 MAX6676 toc05 -15 300 250 1.50 -40 350 TEMP = +25°C 1.75 TEMP = -40°C 1.0 t2 400 2.25 TIME (µs) OUTPUT FREQUENCY (Hz) 2.5 450 MAX6676 toc02 2.50 MAX6676 toc01 3.0 OUTPUT FREQUENCY (kHz) t1 AND t2 TIMES vs. TEMPERATURE MAX6676AUT3 OUTPUT FREQUENCY vs. SUPPLY VOLTAGE 0 -1 -2 1V/div -3 -4 0V -5 VAC = 100mVP-P -6 -1.0 -50 -25 0 25 50 75 TEMPERATURE (°C) 100 125 1 10 100 1k 10k 10ns/div FREQUENCY (Hz) _______________________________________________________________________________________ 3 MAX6676/MAX6677 Typical Operating Characteristics (VCC = 3.0V, TA = +25°C, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC = 3.0V, TA = +25°C, unless otherwise noted.) MAX6677 OUTPUT RISE AND FALL TIMES vs. CAPACITIVE LOAD MAX6677 OUTPUT RISE TIME MAX6676 toc10 MAX6676 toc11 200 CLOAD = 100pF RL = 100kΩ 160 TIME (ns) 1V/div 0 120 RISE 80 40 FALL 0 0 40ns/div 100 300 200 400 500 600 CLOAD (pF) MAX6677 OUTPUT HIGH VOLTAGE vs. TEMPERATURE MAX6677 OUTPUT LOW VOLTAGE vs. TEMPERATURE 3.25 3.00 2.75 350 MAX6676 toc13 ISOURCE = 800µA ISINK = 5mA 300 OUTPUT LOW VOLTAGE (mV) MAX6676 toc12 3.50 OUTPUT HIGH VOLTAGE (V) MAX6676/MAX6677 Low-Voltage, 1.8kHz PWM Output Temperature Sensors 250 200 150 100 ISINK = 1.5mA ISINK = 1mA 50 2.50 0 -40 -15 10 35 60 TEMPERATURE (°C) 4 85 110 -40 -5 30 65 TEMPERATURE (°C) _______________________________________________________________________________________ 100 Low-Voltage, 1.8kHz PWM Output Temperature Sensors PIN NAME FUNCTION 1 DOUT Digital Output Pin. The duty cycle of the output waveform is modulated by temperature. 2, 4, 5, 6 GND Ground. All four ground pins must be connected to GND. 3 VCC Supply Voltage. Bypass VCC to GND with a 0.1µF capacitor. Detailed Description The MAX6676/MAX6677 are high-accuracy, low-current (80µA, typ) temperature sensors ideal for interfacing with µCs or µPs. The MAX6676/MAX6677 convert the ambient temperature into a ratiometric PWM output at a nominal frequency of 1.8kHz (±20%) at +25°C. The time periods, t1 (low) and t2 (high) (Figure 1), are easily read by a µP’s timer/counter port. To calculate the temperature, use the following expression: Temperature (°C) = 398.15 x (t1 / t2) - 273.15 The µC or µP measures the output of the MAX6676/ MAX6677 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. 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 MAX6677 (Figure 2a) has a push-pull output with full CMOS output swings. The ability to source and sink current allows the MAX6677 to drive capacitive loads up to 100pF with less than 1°C error. The MAX6676 (Figure 2b) has an open-drain output. The output capacitance should be minimized in MAX6676 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 MAX6676/MAX6677 and the object being monitored. A precise temperature measurement depends on the thermal resistance between the object being monitored and the MAX6676/ MAX6677 die. Heat flows in and out of plastic packages primarily through the leads. 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. Power Supply from µP Port Pin The low quiescent current of the MAX6676/MAX6677 enables them 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. t2 t1 Figure 1. MAX6676/MAX6677 PWM Output VCC VCC P DOUT DOUT N N (a) (b) MAX6677 MAX6676 Figure 2. Output Configurations _______________________________________________________________________________________ 5 MAX6676/MAX6677 Pin Description MAX6676/MAX6677 Low-Voltage, 1.8kHz PWM Output Temperature Sensors 3.3V VISO VDD VCC MAX6676AUT3 5.1kΩ MAX6676 DOUT DOUT Figure 3. Galvanic Isolation Using an Optocoupler Figure 4. Low-Voltage Logic Galvanic Isolation Multiple Logic Voltages Use an optocoupler to isolate the MAX6676/MAX6677 whenever a high common-mode voltage is present. Choose an optocoupler with equal turn-on and turn-off times. Unequal turn-on/turn-off times produce an error in the temperature reading (Figure 3). Use the MAX6676 open-drain output to drive devices operating at supply voltages other than the MAX6676’s VCC. As shown in Figure 4, connect a pullup resistor from the other supply voltage to the MAX6676 output. Limit the resistor’s current to less than 1mA, thus maintaining an output low logic level of less than 200mV. Thermal Considerations Self-heating may cause the temperature measurement accuracy of the MAX6676/MAX6677 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 is typically 4.0µW operating at 5V with no load. For example, an out load of 3mA creates a maximum error of less than 0.1°C. 6 Chip Information TRANSISTOR COUNT: 2096 PROCESS: BiCMOS _______________________________________________________________________________________ Low-Voltage, 1.8kHz PWM Output Temperature Sensors 6LSOT.EPS 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 © 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX6676/MAX6677 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.)