19-2458; Rev 0; 10/02 PWM Output Temperature Sensors in SC70 Packages Features ♦ Simple Single-Wire PWM Output The MAX6672/MAX6673 operate from 2.4V to 5.5V with a maximum supply current of 150µA. Both devices feature a single-wire output that minimizes the number of pins necessary to interface with a microprocessor. The MAX6672/MAX6673 are available in 5-pin SC70 packages. ♦ Choice of Outputs Open Drain (MAX6672) Push-Pull (MAX6673) ♦ Tiny SC70 Package ♦ Low 60µA (typ) Supply Current Consumption ♦ 1.4kHz Nominal Frequency ♦ 2.4V to 5.5V Supply Range Applications Industrial and Process Control Ordering Information MAX6672AXK-T -40°C to +125°C PINPACKAGE 5 SC70-5 MAX6673AXK-T -40°C to +125°C 5 SC70-5 PART HVAC Automotive TEMP RANGE TOP MARK ACQ ACR Environmental Control Isolated Temperature Sensing Pin Configuration Typical Application Circuit µC VCC * 0.1µF MAX6672 MAX6673 GPIO TO CONTROL SHUTDOWN INPUT TO TIMER/ COUNTER TOP VIEW DOUT 1 N.C. 2 5 VCC 4 GND MAX6672 MAX6673 GND GND 3 SC70 * PULLUP RESISTOR REQUIRED ONLY FOR THE MAX6672. ________________________________________________________________ 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 MAX6672/MAX6673 General Description The MAX6672/MAX6673 are low-current temperature sensors with a single-wire output. These temperature sensors convert the ambient temperature into a 1.4kHz PWM output, which contains the temperature information in its duty cycle. The MAX6672 has an open-drain output and the MAX6673 has a push-pull output. MAX6672/MAX6673 PWM Output Temperature Sensors in SC70 Packages ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC to GND) ................................. -0.3V to +6V DOUT to GND (MAX6672)........................................-0.3V to +6V DOUT to GND (MAX6673)..........................-0.3V to (VCC + 0.3V) DOUT Short to GND ...................................................Continuous ESD Protection (Human Body Model) ............................ ±2000V Continuous Power Dissipation (TA = +70°C) 5-Pin SC70 (derate 2.5mW/°C above +70°C). ............200mW Operating Temperature Range .........................-40°C to +125°C Storage Temperature Range .............................-65°C to +150°C Junction Temperature ......................................................+150°C SC70 Package Vapor Phase (60s) ...................................................... +215°C Infrared (15s). ............................................................. +220°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 = 2.4V to 5.5V, TA = -40°C to +125°C, unless otherwise noted. Typical values specified at +25°C and VCC of 3.3V.) (Note 1) PARAMETER SYMBOL Temperature Error (Note 2) CONDITIONS VCC = 3.3V MIN TYP MAX TA = +25°C to +100°C -3 +3 TA = 0°C to +125°C -4 +4 TA = -20°C to +125°C -5 +5 TA = -40°C to -20°C UNITS °C ±3 Nominal t1 Pulse Width 280 µs Output Low Voltage VOL ISINK = 3mA Output High Voltage VOH ISOURCE = 800µA (MAX6673) Fall Time tFALL CLOAD = 100pF 14 ns Rise Time tRISE CLOAD = 100pF (MAX6673) 96 ns VDOUT = 6V (MAX6672) 0.1 µA 2.5 pF DOUT Open-Drain Leakage Current Output Capacitance Power-Supply Rejection Ratio Supply Current PSRR ICC 0.4 VCC - 0.5 V V 2.4V to 5.5V, TA = -25°C to +125°C 0.3 0.8 2.4V to 3.6V 60 100 3.6V to 5.5V 70 150 °C/V µA Note 1: All specifications are 100% tested at TA = +25°C. Specification limits over temperature (TA = -40°C to +125°C) are guaranteed by design, not production tested. Note 2: Temperature = -200 ✕ (0.85 - T1/T2)3 + (425 ✕ T1/T2) - 273. T1 is the low time period. T2 is the high time period (Figure 1). 2 _______________________________________________________________________________________ PWM Output Temperature Sensors in SC70 Packages NORMALIZED OUTPUT FREQUENCY vs. SUPPLY VOLTAGE 1.25 1.00 MAX6672 toc02 1.005 TA = +125°C 1.000 TA = +25°C 0.995 50 75 100 200 2.0 125 2.5 3.0 OUTPUT ACCURACY vs. TEMPERATURE 4.5 5.0 -50 120 SUPPLY CURRENT (µA) 0 -2 0 25 50 75 100 90 VCC = 5V 60 VCC = 3.3V 125 70 -25 0 25 50 75 100 125 2.0 MAX6672 toc08 POWER-SUPPLY REJECTION (°C/V) MAX6672 toc07 1.0 -25 0 25 50 75 TEMPERATURE (°C) 100 125 3.5 4.0 4.5 0.5 0 -0.5 150 120 5.0 90 MAX6673 RISE TIME 60 30 FALL TIME VAC = 100mVP-P -50 3.0 OUTPUT RISE AND FALL TIMES vs. CAPACITIVE LOAD 0 -1.0 -1.0 2.5 SUPPLY VOLTAGE (V) POWER-SUPPLY REJECTION vs. FREQUENCY -0.5 125 50 -50 POWER-SUPPLY REJECTION vs. TEMPERATURE 0 100 80 TEMPERATURE (°C) 0.5 75 60 TEMPERATURE (°C) 1.0 50 90 0 -25 25 SUPPLY CURRENT vs. SUPPLY VOLTAGE 30 -4 0 100 MAX6672 toc05 150 MAX6672 toc04 VCC = 3.3V -50 -25 TEMPERATURE (°C) SUPPLY CURRENT vs. TEMPERATURE 2 ACCURACY (°C) 4.0 SUPPLY VOLTAGE (V) TEMPERATURE (°C) POWER-SUPPLY REJECTION (°C/V) 3.5 MAX6672 toc06 25 MAX6672 toc09 0 t2 400 t1 SUPPLY CURRENT (µA) -25 500 300 TA = -40°C 0.990 -50 4 t1 AND t2 TIMES (µs) 1.50 600 OUTPUT RISE AND FALL TIMES (ns) FREQUENCY (kHz) 1.75 t1 AND t2 TIMES vs. TEMPERATURE 1.010 NORMALIZED FREQUENCY (kHz) MAX6672 toc01 2.00 MAX6672 toc03 OUTPUT FREQUENCY vs. TEMPERATURE 0.01 0.10 1 10 100 FREQUENCY (Hz) 1k 10k 0.01 0.10 1 10 CAPACITIVE LOAD (nF) _______________________________________________________________________________________ 3 MAX6672/MAX6673 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.) 20 VCC = 5V 15 VCC = 3.3V 10 25 2.0 VCC = 5V 1.5 1.0 0 0 4 8 12 16 20 VCC = 3.3V 0.5 5 TRANSITION FROM +25°C AIR TO +100°C STIRRED OIL BATH VOH = VCC - 0.5V 2.5 SOURCE CURRENT (mA) 50 VOL = 0.4V 25 SINK CURRENT (mA) 75 3.0 MAX6672 toc11 30 MAX6672 toc10 100 MAX6673 OUTPUT SOURCE CURRENT vs. TEMPERATURE MAX6672 toc12 OUTPUT SINK CURRENT vs. TEMPERATURE THERMAL RESPONSE IN STIRRED OIL BATH TEMPERATURE (°C) MAX6672/MAX6673 PWM Output Temperature Sensors in SC70 Packages 0 -50 -25 0 25 50 75 100 125 -50 TEMPERATURE (°C) TIME (s) -25 0 25 50 75 100 125 TEMPERATURE (°C) Pin Description PIN NAME 1 DOUT FUNCTION Digital Output Pin. PWM output, open-drain output (MAX6672), or push-pull output (MAX6673). 2 N.C. 3, 4 GND No Connection. Not internally connected. Pin 3 and Pin 4 must be tied together and connected to ground. 5 VCC Positive Supply. Bypass with a 0.1µF capacitor to GND. Detailed Description The MAX6672/MAX6673 are low-current (60µA, typ), local temperature sensors ideal for interfacing with µCs or µPs. The MAX6672/MAX6673 convert their own temperature into a ratiometric PWM output. The squarewave output waveform time ratio contains the temperature information. The output is a square wave with a nominal frequency of 1.4kHz at +25°C. The temperature is obtained with the following formula: Temperature (°C) = -200 x (0.85 - t1 / t2)3 + (425 x t1 / t2) - 273 Where t1 is a fixed value and t2 is modulated with the temperature. Table 1 lists time ratio vs. temperature. For temperatures greater than +50°C, the temperature error is primarily first order and the following equation can be used: Temperature (°C) = (425 x t1 / t2) - 273 4 The MAX6673 has a push-pull output. The rise and fall times of the MAX6673 output are negligible with respect to the period; therefore, errors caused by capacitive loading are minimized. The output load capacitance should be minimized in MAX6672 applications because the sourcing current is set by the pullup resistor. If the output capacitance becomes too large, unequal rise and fall times distort the pulse width, thus delivering inaccurate readings. Applications Information Pulse-Width Modulation Interfacing with a µC The Typical Application Circuit shows the MAX6672/ MAX6673 interfaced with a µC. In this example, the MAX6672/MAX6673 convert the ambient temperature to a PWM waveform. The µC reads the temperature by measuring the t1 and t2 periods in software and hardware. The only timing requirements are that the clock frequency used for timing measurements is stable and _______________________________________________________________________________________ PWM Output Temperature Sensors in SC70 Packages TIME RATIO (t1/t2) TEMPERATURE (°C) 0.936 125 0.878 100 0.807 70 0.714 30 0.646 0 0.602 -25 0.560 -40 high enough to provide the required measurement resolution. The interface for the MAX6672 requires a pullup resistor. Thermal Response Time The time periods t1 (low) and t2 (high) are values that are easily read by the µP timer/counter. The temperature reading is then calculated using software. Since both periods are obtained consecutively, using the same clock, performing the division indicated in the above formulae results in a ratiometric value that is independent of the exact frequency. Sensing Circuit Board and Ambient Temperatures Temperature sensor ICs such as the MAX6672/ MAX6673 that sense their own die temperatures must be mounted on or close to the object whose temperature they are intended to measure. Because there is a good thermal path between the SC70 package’s metal leads and the IC die, the MAX6672/MAX6673 can accurately measure the temperature of the circuit board to which they are soldered. If the sensor is intended to measure the temperature of a heat-generating component on the circuit board, it should be mounted as close as possible to that component and should share supply and ground traces (if they are not noisy) with that component where possible. This maximizes the heat transfer from the component to the sensor. t2 t1 Figure 1. PWM Waveform Timing Block Diagram 5 VCC PWM MODULATOR TEMPERATURE SENSOR DOUT 1 t2 t1 GND 3, 4 The thermal path between the plastic package and the die is not as good as the path through the leads, so the MAX6672/MAX6673, like all temperature sensors in plastic packages, are less sensitive to the temperature of the surrounding air than they are to the temperature of their leads. They can be successfully used to sense ambient temperature if the circuit board is designed to track the ambient temperature. As with any IC, the wiring and circuits must be kept insulated and dry to avoid leakage and corrosion, especially if the part is operated at cold temperatures where condensation can occur. The error caused by power dissipation in the MAX6672/ MAX6673 is negligible. Chip Information TRANSISTOR COUNT: 601 PROCESS: BiCMOS _______________________________________________________________________________________ 5 MAX6672/MAX6673 Table 1. Time Ratio vs. Temperature 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.) SC70, 5L.EPS MAX6672/MAX6673 PWM Output Temperature Sensors in SC70 Packages 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. 6 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 © 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.