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19-2121; Rev 0; 7/01
12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface
General Description
The MAX6662 is a 12-bit + sign temperature sensor combined with a programmable overtemperature alarm and a 3-wire (SPITM-compatible) serial interface in a single package. It converts its die temperature into digital values using an internal analog-to-digital converter (ADC). The temperature data is stored in a temperature register as a 13-bit word, which allows 0.0625C resolution. The temperature data is readable at any time through the serial interface. The operating temperature range is -55C to +150C. The MAX6662 provides two programmable watchdog interrupt outputs. ALERT is used for lower temperature warning functions, while OT is used for higher temperature-critical functions, such as power-supply shutdown. The MAX6662 features a shutdown mode that saves power by disabling everything except the serial interface. The temperature sensor is available in an 8-pin SO package. o 12-Bit + Sign, 0.0625C Resolution o Accuracy 1C max (+30C to +50C) 1.6C max (0C to +70C) 2.5C max (-20C to +85C) 2.5 typ (+150C) o Extended Temperature Measurement Range -55C to +150C o Low Average Supply Current, 125A (typ) o Shutdown Mode to Minimize Power Consumption in Portable Applications o Two Programmable Temperature Fault Outputs o Switchable Fault Queue to Eliminate False Tripping in Noisy Environments
Features
MAX6662
Applications
HVAC Refrigeration Automotive Test Equipment
PART MAX6662MSA
Ordering Information
TEMP. RANGE -55C to +150C PIN-PACKAGE 8 SO
Typical Operating Circuit
VCC = +3V TO +5.5V
Pin Configuration
TOP VIEW
0.1F 10k VCC OT HEAT SOURCES MAX6662 ALERT SIO SCLK CS 10k SCLK CS SIO 1 2 8 7 VCC NC ALERT OT
MAX6662
3 6 5
SYSTEM CONTROLLER
GND 4
SO
SPI is a trademark of Motorola, Inc. ________________________________________________________________ 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.
12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface MAX6662
ABSOLUTE MAXIMUM RATINGS
All Voltages Are Referenced to GND VCC ...........................................................................-0.3V to +6V ALERT, OT................................................................-0.3V to +6V SIO, SCLK, CS............................................-0.3V to (VCC + 0.3V) SIO Current .......................................................-10mA to +50mA Continuous Current into Any Pin (except NC)....................10mA Continuous Power Dissipation (TA = +70C) 8-Pin SO (derate 5.9mW/C above +70C)..................471mW Operating Temperature Range (Note 1) ..........-55C to +150C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
Note 1: The MAX6662 is not recommended to operate above +125C for an extended period of time.
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 = +3V to +5.5V, TA = -55C to +125C, unless otherwise noted. Typical values are at TA = +25C and VCC = +3.3V.)
PARAMETER SYMBOL CONDITIONS +30C TA +50C, VCC = +3.3V 0C TA +70C, VCC = +3.3V Accuracy -20C TA +85C, VCC = +3.3V -40C TA +100C, VCC = +3.3V -55C TA +125C, VCC = +3.3V TA +150C, VCC = +3.3V Power-Supply Rejection Ratio Resolution Supply Voltage Range Average Operating Current VCC VCC = +5.5V VCC = +3.0V VCC = +5.5V VCC = +3.0V VCC = +5.5V VCC = +3.0V Power-On-Reset Threshold Power-On-Reset Threshold Hysteresis Conversion Time Temperature Update Frequency SERIAL INTERFACE (SIO, SCLK, CS, ALERT, OT) Input Low Voltage Input High Voltage Input/Output Leakage Current Input Capacitance Output Low Sink Current Output High Voltage Output Low Voltage VIL VIH ILEAK Cin IOL VOH VOL ALERT, OT, VOL = 0.6V ISIO = 1.6mA source ISIO = 1.6mA sink 3 VCC - 0.4 0.4 VIN = GND or VCC 0.7 VCC -5 5 +5 0.8 V V A pF mA V V tCONV VPOR 3.0 150 125 300 300 8 4 2.0 90 0.25 2 600 500 22 A 15 2.5 V mV s Hz PSRR MIN -1.0 -1.6 -2.5 -3.0 -4.0 TYP 0.4 0.7 1.0 1.2 1.5 2.5 0.2 0.0625 5.5 0.5 C/V C V A MAX +1.0 +1.6 +2.5 +3.0 +4.0 C UNITS
TEMPERATURE TO DIGITAL-CONVERTER CHARACTERISTICS
Peak Operating Current (Note 2)
A
Shutdown Supply Current
2
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12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +3V to +5.5V, TA = -55C to +125C, unless otherwise noted. Typical values are at TA = +25C and VCC = +3.3V.)
PARAMETER SERIAL INTERFACE TIMING Serial Clock Frequency SCLK High Pulse Width SCLK Low Pulse Width CS High Pulse Width SCLK Fall to Output Data Valid CS Fall to SCLK Rise CS Rise to Output Disable CS to SCLK Hold Time SIO to SCLK Setup Time SIO to SCLK Hold Time Output Fall Time fSCLK tCH tCL tCSW tDO tCSS tTR tCSH tDS tDH tF CLOAD = 100pF 0 100 0 10 CLOAD = 100pF 100 100 200 200 200 100 2.5 MHz ns ns ns ns ns ns ns ns ns ns SYMBOL CONDITIONS MIN TYP MAX UNITS
MAX6662
Note 2: Peak operating current measured during conversion.
Typical Operating Characteristics
(VCC = +3V, TA = +25C, unless otherwise noted.)
TEMPERATURE ERROR VS. TEMPERATURE
MAX6662 toc01
TEMPERATURE ERROR DISTRIBTUTION
80 PERCENTAGE OF SAMPLES (%) 70 60 50 40 30 20 10 NOTE: DEVICES TRIMMED AT TA = +30C 200 SAMPLES
MAX6662 toc02
SUPPLY CURRENT VS. TEMPERATURE
AVERAGE OVER 2 180 SUPPLY CURRENT (A) VCC = +5.0V 160
MAX6662 toc03
3 2 1 0 -1 -2 -3 VCC = +5.0V VCC = +3.3V VCC = +3.0V
90
200
TEMPERATURE ERROR (C)
TA = +30C
140 VCC = +3.3V 120 VCC = +3.0V 100
0 -50 -30 -10 10 30 50 70 90 110 130 150 TEMPERATURE (C) -0.45-0.35 -0.25 -0.15 0.05 0.15 0.25 0.35 0.45 TEMPERATURE ERROR (C)
-50
0
50 TEMPERATURE (C)
100
150
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3
12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface MAX6662
Typical Operating Characteristics (continued)
(VCC = +3V, TA = +25C, unless otherwise noted.) SHUTDOWN CURRENT VS. TEMPERATURE
MAX6662 toc04
12 10 SHUTDOWN CURRENT (A) VCC = +5.0V 8 6 4 2 VCC = +3.0V 0 -50 0 50 TEMPERATURE (C) 100 VCC = +3.3V
150
Pin Description
PIN 1 2 3 4 5 6 7 8 NAME SCLK CS SIO GND OT ALERT NC VCC Serial-Clock Input Chip Select Input. Set low to enable the serial interface for data input/output. Serial-Data Input/Output. Bidirectional data input and output for serial interface. Ground Overtemperature Output. Open-drain output requires a pullup resistor to VCC. Alert Output. Open-drain output requires a pullup resistor to VCC. No Connection. Do not make a connection to this pin. Supply Voltage Input. Bypass to GND with a 0.1F capacitor as close to VCC as possible. FUNCTION
Detailed Description
The MAX6662 continuously converts its die temperature into a digital value using its integrated ADC. Temperature data is updated twice a second. The resulting data is readable at any time through the SPIcompatible serial interface. Figure 1 shows the simplified functional diagram of the MAX6662. Its internal current sources force 100A and 10A currents through a diode (diode-connected transistor), while the integrating ADC measures the voltage difference. The difference in voltage corresponds to the die temperature. The result is stored in the Temperature register. The control logic unit compares the temperature and the temperature limit settings stored in the registers to determine whether a fault condition has occurred.
Temperature Fault Alert
The ALERT is an open-drain active-low (default, also programmable active-high) output used to alert the system to temperature faults. ALERT can be programmed to operate in either one of two modes: comparator or interrupt mode. Interrupt Mode In the interrupt mode, the MAX6662 ALERT pin asserts an alarm for an undertemperature (TLOW) fault, as well as for an overtemperature (THIGH) fault. Once either fault has occurred, it remains active indefinitely, regardless of condition. ALERT is unconditionally deasserted (even if Temperature is still out of limits) by reading the temperature register. ALERT only asserts again if the temperature crosses the hysteresis, thereby corresponding to the fault (TLOW or THIGH) that initially set the ALERT.
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12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface MAX6662
VCC
OT
12 -BIT + SIGN ADC ALERT
TEMPERATURE TLOW SIO SCLK CS
THIGH
TMAX
THYST CONFIGURATION
SERIAL INTERFACE
Figure 1. MAX6662 Simplified Functional Diagram
For example: If THIGH is set to 100C and THYST is set to 20C, ALERT does not assert until temperature exceeds 100C. If the temperature is then read through the serial interface, ALERT deasserts. ALERT asserts again when temperature is less than 80C (Figure 2). Comparator Mode In the comparator mode, ALERT is asserted when temperature exceeds the value in the THIGH register, or is lower than the value in the T LOW register. ALERT deasserts when temperature is less than THIGH - THYST or greater than TLOW + THYST. Reading the registers does not deassert ALERT. For example: If THIGH is set to 100C and TLOW is set to 80C, ALERT does not assert until temperature exceeds 100C, or is below 80C. Then, ALERT only deasserts if temperature is less than THIGH - THYST or greater than TLOW + THYST.
Overtemperature Alert
OT operates only in comparator mode. The OT pin is asserted when the temperature exceeds TMAX, and deasserted when the temperature drops below TMAX - THYST. A read operation does not reset OT. OT is an open-drain active-low (default) output, but can be programmed to active-high.
THIGH THIGH - THYST TEMPERATURE
TLOW + THYST TLOW ALERT
* TEMPERATURE READ
*
* * LAST INTERRUPT MISSED, BUT THRESHOLD STILL CHANGES TO THIGH.
Figure 2. Example of ALERT Operation in Interrupt Mode _______________________________________________________________________________________ 5
12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface MAX6662
Temperature Fault Queue
The activation of ALERT and OT is subject to the depth of the fault queue. If the Fault Queue bit in the Configuration register is enabled, ALERT or OT does not assert until four consecutive temperature conversions are at fault. For example: If THIGH is set to 100C, THYST is set to 20C, ALERT is set to interrupt mode, and fault queue is enabled, ALERT does not assert until four consecutive conversions exceed 100C. If the temperature is then read through the serial interface, ALERT deasserts. ALERT asserts again when four consecutive conversions are less than 80C.
Serial Interface Protocol
The serial interface consists of three signal lines: chip select (CS), bidirectional data line (SIO), and serial clock (SCLK). Only the master (external) drives CS and SCLK. Both the master and the MAX6662 drive SIO. When CS is high, the MAX6662 does not respond to any activity on clock and data lines. When CS goes low, a transaction begins. A valid transaction has 24 clock cycles provided from SCLK after CS goes low--no more and no fewer. Any communication with more or fewer than exactly 24 clocks is ignored. Data is clocked in to the MAX6662 at the rising edge of SCLK when the master is writing. Data is clocked out at the falling edge of SCLK when the master is reading. Both the command byte and data word are clocked in (or out) with the most-significant bit (MSB) bit first. The first eight clock cycles are dedicated to the command byte (1 bit per cycle). This command byte is input to the MAX6662 through the SIO. Sixteen cycles of data follow. The 16 cycles of data are either driven by the master or by the MAX6662, depending on the command byte. If the MAX6662 is driving the SIO, it starts driving at the falling edge of the eighth clock up until the rising edge of CS. Data is available on the falling edge of the eighth clock cycle. Figure 3 depicts a valid serial interface transaction and Figure 4 is the serial interface timing diagram.
tCSW CS
Shutdown Mode
The MAX6662 features a programmable shutdown mode. Set the Shutdown bit in the Configuration register to 1 to shut down. In the shutdown mode, everything is disabled except the power-on reset (POR) and the serial interface. In the shutdown mode, information stored in all registers is retained. The Temperature register retains the temperature from the last conversion result.
CS 1 SCLK SIO COMMAND BYTE (8 BITS) DATA WORD (16 BITS)
tCSS SCLK tCH SIO tDS tF tDH tCL tTR
2
3
4
5
6
7
8
9
10
23 24
tCSH
Figure 3. MAX6662 Serial Interface Operation
tDO
Figure 4. Detailed Serial Interface Timing Diagram
Table 1. Bit Descriptions of the Configuration Register
BIT 15 to 13 12 11 10 9 8 7 to 0 POR 0 0 0 0 0 0 0 Reserved. Writing to these bits is ignored. Fault Queue bit. Set to 1 to enable queue. ALERT polarity bit. Set to 1 for active-high ALERT output. Default is 0 for the ALERT output active-low. OT polarity bit. Set to 1 for active-high OT output. Default is 0 for the OT output active-low. Interrupt Mode bit. Set to 1 to enable the interrupt mode. Default is 0 for the comparator mode. Shutdown bit. Set to 1 to shut down the MAX6662. Reserved. Writing to these bits is ignored. DESCRIPTION
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12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface
Table 2. Command Codes for the Temperature Limit Registers
COMMAND C1h C3h C5h C7h C9h CBh 83h 85h 87h 89h 8Bh DESCRIPTION Temperature register read Configuration register read THYST register read TMAX register read TLOW register read THIGH register read Configuration register write THYST register write TMAX register write TLOW register write THIGH register write
The first bit of the command byte is always high to signify a Start, and the second bit is an R/W bit, high for read and low for write. There are a total of 11 valid commands. The temperature conversion runs continuously and asynchronously from the serial interface. When the Temperature register is read, any conversion in progress is aborted and the data output is from the previous conversion. A new conversion is started each time the serial interface is accessed.
MAX6662
MAX6662 Registers
The MAX6662 has six registers: Temperature, Configuration, THYST, TMAX, TLOW, and THIGH registers. They are all 16 bits (Figure 5). The Temperature register is read only; all other registers can be read from or written to. Temperature Register The MSB of the Temperature register is the sign bit. The next 12 bits are temperature data. The digital temperature data for the most recent temperature conversion is
TEMPERATURE REGISTER (COMMAND = C1H) Label POR State 15 Sign Bit 0 14 Data MSB 0 13 12 11 10 9 8 7 6 5 4 1 0 3 2 Data TOVER THIGH TLOW LSB Flag Flag Flag 0 0 0 0
0
0
0
0
0
0
0
0
0
0
Label POR State
CONFIGURATION REGISTER (COMMAND = C3H FOR READING; COMMAND = 83H FOR WRITING) 15 14 13 12 11 10 9 8 7 6 5 4 3 2 * * * Fault ALERT OT Interrupt Shutdown * * * * * * Queue Polarity Polarity Mode Mode 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1 *
0 *
0
0
TEMPERATURE LIMIT REGISTERS (THYST, TMAX, TLOW, THIGH) (TABLE 2) Label POR State
* Reserved (not used). Writing to this bit is ignored. ** THYST register: 0000 0001 0000 0000b (2C) ** TMAX register: 0010 1000 0000 0000b (+80C) ** TLOW register: 0000 0101 0000 0000b (+10C) ** THIGH register: 0010 0000 0000 0000b (+64C)
15 Sign
14 Data MSB
13
12
11
10
9
8
7 Data LSB **
6 *
5 *
4 *
3 *
2 *
1 *
0 *
Figure 5. Bit Assignment for the MAX6662 Registers _______________________________________________________________________________________ 7
12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface MAX6662
Table 3. Output Code vs. Temperature
TEMPERATURE (C) +150.0000 +125.0000 +25.0000 +0.0625 0.0000 -0.0625 -25.0000 -55.0000 BINARY CODE 0100 1011 0000 0xxx 0011 1110 1000 0xxx 0000 1100 1000 0xxx 0000 0000 0000 1xxx 0000 0000 0000 0xxx 1111 1111 1111 1xxx 1111 0011 0111 0xxx 1111 1100 0111 0xxx
The MAX6662 supply current is typically 125A when the serial interface is active. When driving high-impedance loads, the devices dissipate negligible power; therefore, the die temperature is essentially the same as the package temperature. The key to accurate temperature monitoring is good thermal contact between the MAX6662 package and the monitored device or circuit. Heat flows in and out of plastic packages primarily through the leads. Short, wide copper traces leading to the temperature monitor ensure that heat transfers quickly and reliably. The rise in die temperature due to self-heating is given by the following formula: TJ = PDISSIPATION x JA where P DISSIPATION is the power dissipated by the MAX6662, and JA is the package's thermal resistance. The typical thermal resistance is +170C/W for the 8-pin SO package. To limit the effects of self-heating, minimize the output currents. For example, if the MAX6662 sinks 4mA with the maximum ALERT voltage specification of 0.8V, an additional 3.2mW of power is dissipated within the IC. This corresponds to a 0.54C rise in the die temperature.
stored in the Temperature register and is in C, using a two's-complement format with 1LSB corresponding to 0.0625C (Table 3). The three least-significant bits (LSBs) are temperature status (flag) bits. The Temperature register is read only. Set the command byte to C1h for reading the Temperature register. Configuration Register The Configuration register uses only 5 bits, bits 8 to 12. Table 1 describes its function. Bit 8 is the shutdown bit and should be set to 1 to shut down the entire MAX6662 except the serial interface and POR. Bit 12 is the fault queue bit. When the Fault Queue bit is 1, the ALERT and OT outputs are asserted if four consecutive temperature faults occurred. The Configuration register can be read or written to. Writing to unused bits is ignored. Set the command byte to C3h for reading from this register; set the command byte to 83h for writing to this register. Temperature-Limit Registers The High-Temperature (T HIGH ), Low-Temperature (TLOW), and the Hysteresis (THYST) registers set the temperature limit for triggering the ALERT (Figure 1). The Maximum-Temperature (TMAX) and Hysteresis registers set the temperature threshold for the OT output. These temperature-limit registers use the 9MSB bits (8 bits + sign) for setting temperature values in two's complement format with 1C resolution. The 7LSBs are ignored. These registers can be read or written to. Table 2 shows the command bytes for reading and writing to these registers.
Chip Information
TRANSISTOR COUNT: Bipolar: 182 MOS: 10177 PROCESS: BiCMOS
Applications Information
8 _______________________________________________________________________________________
12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface
Package Information
MAX6662
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 _____________________ 9 (c) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
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