View MAX6676_15754.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

19-2660; Rev 1; 1/03
Low-Voltage, 1.8kHz PWM Output Temperature Sensors
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 80A. All 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 1.8kHz (20%) at +25C. The output format is decoded as follows: Temperature (C) = 398.15 (t1 / t2) - 273.15 Where t1 is fixed with a typical value of 0.24ms and t2 is modulated by the temperature. The MAX6676/ MAX6677 operate from -40C to +125C and are available in space-saving 6-pin SOT23 packages.
Features
o Simple Single-Wire, 1.8kHz PWM Output o Operates Down to 1.8V o High Accuracy 1.5C at TA = +25C 3.0C at TA = 0C to +85C o Operates from -40C to +125C o Low 80A Typical Current Consumption o Small 6-Pin SOT23 Package
MAX6676/MAX6677
Ordering Information
PART MAX6676AUT3-T MAX6676AUT5-T MAX6677AUT3-T TEMP RANGE -40C to +125C -40C to +125C -40C to +125C PINPACKAGE 6 SOT23-6 6 SOT23-6 6 SOT23-6
Applications
Process Control Industrial HVAC and Environmental Control Automotive Portable Devices P and C Temperature Monitoring Isolated Temperature Sensing
MAX6676AUT3 MAX6676AUT5 MAX6677AUT3 Open drain Open drain Push-pull PART OUTPUT TYPE
Selector Guide
SUPPLY VOLTAGE RANGE (V) 1.8 to 3.6 3.6 to 5.5 1.8 to 3.6 TOP MARK ABBF ABBG ABBH
Typical Operating Circuit
VCC
Pin Configuration
TOP VIEW
VCC DOUT 0.1F
5.1k* INPUT TO TIMER/COUNTER t2 t1 C
DOUT 1
6
GND
MAX6676
GND 2
MAX6676 MAX6677
5
GND
GND
VCC 3
4
GND
SOT23
*REQUIRED ONLY FOR MAX6676.
________________________________________________________________ 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.
Low-Voltage, 1.8kHz PWM Output Temperature Sensors MAX6676/MAX6677
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 = +70C) 6-Pin SOT23 (derate 8.7mW/C above +70C).........695.7mW Operating Temperature Range .........................-40C to +125C 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 = 1.8V to 3.6V (MAX6676AUT3/MAX6677AUT3), VCC = 3.6V to 5.5V (MAX6676AUT5), TA = -40C to +125C, unless otherwise noted. Typical values are at VCC = 3.0V (MAX6676AUT3/MAX6677AUT3), VCC = 5.0V (MAX6676AUT5), TA = +25C.)
PARAMETER Supply Voltage Range Supply Current SYMBOL VCC ICC MAX6676AUT5 RL = TA = +25C Temperature Error TA = 0C to +85C TA = -20C to +100C TA = -40C to +125C Nominal t1 Pulse Width Output High Voltage Output Leakage Current Output Low Voltage Fall Time Rise Time Digital Output Capacitance Power-Supply Rejection Ratio VOL tF tR COUT PSRR VCC = 1.8V - 3.6V -1.2 VOH IOH = 800A, MAX6677 VOUT = VCC IOL = 3mA CL = 100pF, RL = 10k MAX6676, CL = 15pF, RL = 10k MAX6677, CL = 100pF, RL = 10k 20 300 30 15 +0.4 +1.2 VCC 0.3 0.1 0.3 -1.5 -3.0 -4.2 -5.5 240 CONDITIONS MAX6676AUT3/MAX6677AUT3 MIN 1.8 3.6 80 TYP MAX 3.6 5.5 200 +1.5 +3.0 +4.2 +5.5 s V A V ns ns pF C/V C UNITS V A
Note 1: Parts are tested at +25C. Specifications are guaranteed by design over temperature.
2
_______________________________________________________________________________________
Low-Voltage, 1.8kHz PWM Output Temperature Sensors
Typical Operating Characteristics
(VCC = 3.0V, TA = +25C, unless otherwise noted.)
OUTPUT FREQUENCY vs. TEMPERATURE
MAX6676 toc01
MAX6676/MAX6677
MAX6676AUT3 OUTPUT FREQUENCY vs. SUPPLY VOLTAGE
MAX6676 toc02
t1 AND t2 TIMES vs. TEMPERATURE
MAX6676 toc03
3.0
2.50
450 t2
OUTPUT FREQUENCY (kHz)
400
OUTPUT FREQUENCY (Hz)
2.5
2.25 TIME (s) TEMP = +125C 2.00 TEMP = +25C 1.75 TEMP = -40C 250 t1 350
2.0
300
1.5
1.0 -40 -15 10 35 60 85 110 TEMPERATURE (C)
1.50 1.8 2.1 2.4 2.7 3.0 3.3 3.6 SUPPLY VOLTAGE (V)
200 -40 -15 10 35 60 85 110 TEMPERATURE (C)
OUTPUT ACCURACY vs. TEMPERATURE
MAX6676 toc04
MAX6676AUT3 SUPPLY CURRENT vs. TEMPERATURE
MAX6676 toc05
MAX6676AUT3 SUPPLY CURRENT vs. SUPPLY VOLTAGE
400 SUPPLY CURRENT (A) 350 300 250 200 150 100 5.1k PULLUP
MAX6676 toc06
5
600 500 SUPPLY CURRENT (A) 400 300 VCC = 3.0V 200 100 5.1k PULLUP RESISTOR VCC = 1.8V VCC = 3.6V
450
OUTPUT ACCURACY (C)
3
1
-1
-3
50 0 1.8
NO PULLUP 2.1 2.4 2.7 3.0 3.3 3.6
-5 -40 -15 10 35 60 85 110 TEMPERATURE (C)
0 -40 -15 10 35 60 85 110 TEMPERATURE (C)
SUPPLY VOLTAGE (V)
POWER-SUPPLY REJECTION RATIO vs. TEMPERATURE
MAX6676 toc07
POWER-SUPPLY REJECTION RATIO vs. FREQUENCY
MAX6676 toc08
OUTPUT FALL TIME (CL = 100pF, RL = 100k)
MAX6676 toc09
1.0
2 1 CHANGE IN TEMPERATURE (C) 0 -1 -2 -3 -4 -5
0.5 PSRR (C/V)
0
1V/div
-0.5
0V VAC = 100mVP-P 1 10 100 FREQUENCY (Hz) 1k 10k 10ns/div
-1.0 -50 -25 0 25 50 75 100 125 TEMPERATURE (C)
-6
_______________________________________________________________________________________
3
Low-Voltage, 1.8kHz PWM Output Temperature Sensors MAX6676/MAX6677
Typical Operating Characteristics (continued)
(VCC = 3.0V, TA = +25C, unless otherwise noted.)
MAX6677 OUTPUT RISE TIME
MAX6676 toc10
MAX6677 OUTPUT RISE AND FALL TIMES vs. CAPACITIVE LOAD
MAX6676 toc11
200
CLOAD = 100pF RL = 100k 160 1V/div TIME (ns) 120 RISE 80
0
40
FALL
0 40ns/div 0 100 200 300 CLOAD (pF) 400 500 600
MAX6677 OUTPUT HIGH VOLTAGE vs. TEMPERATURE
MAX6676 toc12
MAX6677 OUTPUT LOW VOLTAGE vs. TEMPERATURE
MAX6676 toc13
3.50 ISOURCE = 800A OUTPUT HIGH VOLTAGE (V) 3.25
350 300 OUTPUT LOW VOLTAGE (mV) 250 200 150 100 50 ISINK = 1.5mA ISINK = 5mA
3.00
2.75
ISINK = 1mA
2.50 -40 -15 10 35 60 85 110 TEMPERATURE (C)
0 -40 -5 30 65 100 TEMPERATURE (C)
4
_______________________________________________________________________________________
Low-Voltage, 1.8kHz PWM Output Temperature Sensors
Pin Description
PIN 1 NAME DOUT FUNCTION Digital Output Pin. The duty cycle of the output waveform is modulated by temperature. Ground. All four ground pins must be connected to GND. Supply Voltage. Bypass VCC to GND with a 0.1F capacitor.
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.
MAX6676/MAX6677
2, 4, 5, 6 3
GND VCC
Detailed Description
The MAX6676/MAX6677 are high-accuracy, low-current (80A, typ) temperature sensors ideal for interfacing with Cs or Ps. The MAX6676/MAX6677 convert the ambient temperature into a ratiometric PWM output at a nominal frequency of 1.8kHz (20%) at +25C. The time periods, t1 (low) and t2 (high) (Figure 1), are easily read by a P's timer/counter port. To calculate the temperature, use the following expression: Temperature (C) = 398.15 x (t1 / t2) - 273.15 The C or P 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 1C 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.
Power Supply from P 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 0.1F power-supply bypass capacitance.
t2
t1
Figure 1. MAX6676/MAX6677 PWM Output
VCC
VCC
P DOUT N N DOUT
(a) MAX6677
(b) MAX6676
Figure 2. Output Configurations
_______________________________________________________________________________________
5
Low-Voltage, 1.8kHz PWM Output Temperature Sensors MAX6676/MAX6677
3.3V VISO
VCC
VDD
MAX6676AUT3 DOUT
5.1k MAX6676 DOUT
Figure 3. Galvanic Isolation Using an Optocoupler
Figure 4. Low-Voltage Logic
Galvanic Isolation
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).
Multiple Logic Voltages
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, +140C/W), the mounting technique, and the airflow. Static dissipation is typically 4.0W operating at 5V with no load. For example, an out load of 3mA creates a maximum error of less than 0.1C.
Chip Information
TRANSISTOR COUNT: 2096 PROCESS: BiCMOS
6
_______________________________________________________________________________________
Low-Voltage, 1.8kHz PWM Output Temperature Sensors
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.)
6LSOT.EPS
MAX6676/MAX6677
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) 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

▲Up To Search▲

Price & Availability of MAX6676

	To Download MAX6676 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .