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| 19-2458; Rev 0; 10/02 PWM Output Temperature Sensors in SC70 Packages 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. The MAX6672/MAX6673 operate from 2.4V to 5.5V with a maximum supply current of 150A. 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. o Simple Single-Wire PWM Output o Tiny SC70 Package o Low 60A (typ) Supply Current Consumption o 1.4kHz Nominal Frequency o Choice of Outputs Open Drain (MAX6672) Push-Pull (MAX6673) o 2.4V to 5.5V Supply Range Features MAX6672/MAX6673 Applications Industrial and Process Control HVAC Automotive Environmental Control Isolated Temperature Sensing PART Ordering Information TEMP RANGE PINPACKAGE 5 SC70-5 5 SC70-5 TOP MARK ACQ ACR MAX6672AXK-T -40C to +125C MAX6673AXK-T -40C to +125C Typical Application Circuit Pin Configuration C VCC * 0.1F MAX6672 MAX6673 GND GPIO TO CONTROL SHUTDOWN INPUT TO TIMER/ COUNTER TOP VIEW DOUT 1 5 VCC N.C. 2 MAX6672 MAX6673 4 GND GND 3 SC70 * PULLUP RESISTOR REQUIRED ONLY FOR THE MAX6672. ________________________________________________________________ Maxim Integrated Products 1 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. PWM Output Temperature Sensors in SC70 Packages MAX6672/MAX6673 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 = +70C) 5-Pin SC70 (derate 2.5mW/C above +70C). ............200mW Operating Temperature Range .........................-40C to +125C Storage Temperature Range .............................-65C to +150C Junction Temperature ......................................................+150C SC70 Package Vapor Phase (60s) ...................................................... +215C Infrared (15s). ............................................................. +220C 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 = 2.4V to 5.5V, TA = -40C to +125C, unless otherwise noted. Typical values specified at +25C and VCC of 3.3V.) (Note 1) PARAMETER Temperature Error (Note 2) Nominal t1 Pulse Width Output Low Voltage Output High Voltage Fall Time Rise Time DOUT Open-Drain Leakage Current Output Capacitance Power-Supply Rejection Ratio Supply Current PSRR ICC 2.4V to 5.5V, TA = -25C to +125C 2.4V to 3.6V 3.6V to 5.5V VOL VOH tFALL tRISE ISINK = 3mA ISOURCE = 800A (MAX6673) CLOAD = 100pF CLOAD = 100pF (MAX6673) VDOUT = 6V (MAX6672) VCC - 0.5 14 96 0.1 2.5 0.3 60 70 0.8 100 150 SYMBOL CONDITIONS TA = +25C to +100C VCC = 3.3V TA = 0C to +125C TA = -20C to +125C TA = -40C to -20C MIN -3 -4 -5 3 280 0.4 s V V ns ns A pF C/V A TYP MAX +3 +4 +5 C UNITS Note 1: All specifications are 100% tested at TA = +25C. Specification limits over temperature (TA = -40C to +125C) 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 Typical Operating Characteristics (VCC = 3.3V, TA = +25C, unless otherwise noted.) NORMALIZED OUTPUT FREQUENCY vs. SUPPLY VOLTAGE MAX6672 toc02 MAX6672/MAX6673 OUTPUT FREQUENCY vs. TEMPERATURE MAX6672 toc01 t1 AND t2 TIMES vs. TEMPERATURE MAX6672 toc03 2.00 1.010 NORMALIZED FREQUENCY (kHz) 600 TA = +125C 1.000 TA = +25C 0.995 TA = -40C t1 AND t2 TIMES (s) 1.75 FREQUENCY (kHz) 1.005 500 t2 400 1.50 1.25 300 t1 200 1.00 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) 0.990 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) -50 -25 0 25 50 75 100 125 TEMPERATURE (C) OUTPUT ACCURACY vs. TEMPERATURE MAX6672 toc04 SUPPLY CURRENT vs. TEMPERATURE MAX6672 toc05 SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX6672 toc06 4 VCC = 3.3V 150 100 SUPPLY CURRENT (A) 90 VCC = 5V 60 VCC = 3.3V 30 SUPPLY CURRENT (A) 75 100 125 2 ACCURACY (C) 120 90 80 0 70 -2 60 -4 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) 0 -50 -25 0 25 50 TEMPERATURE (C) 50 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) POWER-SUPPLY REJECTION vs. TEMPERATURE MAX6672 toc07 POWER-SUPPLY REJECTION vs. FREQUENCY MAX6672 toc08 OUTPUT RISE AND FALL TIMES vs. CAPACITIVE LOAD MAX6672 toc09 1.0 POWER-SUPPLY REJECTION (C/V) 1.0 POWER-SUPPLY REJECTION (C/V) 150 OUTPUT RISE AND FALL TIMES (ns) 0.5 0.5 120 90 MAX6673 RISE TIME 60 0 0 -0.5 -0.5 VAC = 100mVP-P 30 FALL TIME 0 -1.0 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) -1.0 0.01 0.10 1 10 100 1k 10k FREQUENCY (Hz) 0.01 0.10 1 10 CAPACITIVE LOAD (nF) _______________________________________________________________________________________ 3 PWM Output Temperature Sensors in SC70 Packages MAX6672/MAX6673 Typical Operating Characteristics (continued) (VCC = 3.3V, TA = +25C, unless otherwise noted.) THERMAL RESPONSE IN STIRRED OIL BATH MAX6672 toc10 OUTPUT SINK CURRENT vs. TEMPERATURE MAX6672 toc11 MAX6673 OUTPUT SOURCE CURRENT vs. TEMPERATURE VOH = VCC - 0.5V MAX6672 toc12 100 30 25 SINK CURRENT (mA) 20 15 VOL = 0.4V 3.0 2.5 SOURCE CURRENT (mA) 2.0 TEMPERATURE (C) 75 VCC = 5V VCC = 5V 1.5 1.0 0.5 0 VCC = 3.3V VCC = 3.3V 10 5 0 50 TRANSITION FROM +25C AIR TO +100C STIRRED OIL BATH 25 0 4 8 12 TIME (s) 16 20 -50 -25 0 25 50 75 100 125 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) TEMPERATURE (C) Pin Description PIN 1 2 3, 4 5 NAME DOUT N.C. GND VCC No Connection. Not internally connected. Pin 3 and Pin 4 must be tied together and connected to ground. Positive Supply. Bypass with a 0.1F capacitor to GND. FUNCTION Digital Output Pin. PWM output, open-drain output (MAX6672), or push-pull output (MAX6673). Detailed Description The MAX6672/MAX6673 are low-current (60A, typ), local temperature sensors ideal for interfacing with Cs or Ps. 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 +25C. 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 +50C, the temperature error is primarily first order and the following equation can be used: Temperature (C) = (425 x t1 / t2) - 273 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 C The Typical Application Circuit shows the MAX6672/ MAX6673 interfaced with a C. In this example, the MAX6672/MAX6673 convert the ambient temperature to a PWM waveform. The C 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 4 _______________________________________________________________________________________ PWM Output Temperature Sensors in SC70 Packages Table 1. Time Ratio vs. Temperature TIME RATIO (t1/t2) 0.936 0.878 0.807 0.714 0.646 0.602 0.560 TEMPERATURE (C) 125 100 70 30 0 -25 -40 5 VCC MAX6672/MAX6673 t2 t1 Figure 1. PWM Waveform Timing Block Diagram 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 P 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. TEMPERATURE SENSOR PWM MODULATOR DOUT 1 t2 GND 3, 4 t1 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. 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 PWM Output Temperature Sensors in SC70 Packages MAX6672/MAX6673 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 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 (c) 2002 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. |
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