MAX6662中文资料

General Description

The MAX6662 is a 12-bit + sign temperature sensor combined with a programmable overtemperature alarm and a 3-wire (SPI?-compatible) serial interface in a sin-gle 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 0.0625°C resolu-tion. The temperature data is readable at any time through the serial interface. The operating temperature range is -55°C to +150°C.

The MAX6662 provides two programmable watchdog interrupt outputs. ALERT is used for lower temperature warning functions, while OT is used for higher tempera-ture-critical functions, such as power-supply shutdown.The MAX6662 features a shutdown mode that saves power by disabling everything except the serial inter-face.The temperature sensor is available in an 8-pin SO package.

Applications

HVAC Refrigeration Automotive Test Equipment

Features

o 12-Bit + Sign, 0.0625°C Resolution o Accuracy

±1°C max (+30°C to +50°C)±1.6°C max (0°C to +70°C)±2.5°C max (-20°C to +85°C)±2.5 typ (+150°C)

o Extended Temperature Measurement Range

-55°C to +150°C o Low Average Supply Current, 125μA (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

MAX6662

12-Bit + Sign Temperature Sensor with

SPI-Compatible Serial Interface

________________________________________________________________Maxim Integrated Products

1

Pin Configuration

Ordering Information

Typical Operating Circuit

19-2121; Rev 0; 7/01

SPI is a trademark of Motorola, Inc.

For pricing, delivery, and ordering information,please contact Maxim/Dallas Direct!at 1-888-629-4642, or visit Maxim’s website at https://www.wendangku.net/doc/eb5115074.html,.

M A X 6662

12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

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.

All Voltages Are Referenced to GND

V CC ...........................................................................-0.3V to +6V ALERT , OT ................................................................-0.3V to +6V SIO, SCLK, CS ............................................-0.3V to (V CC + 0.3V)SIO Current.......................................................-10mA to +50mA Continuous Current into Any Pin (except NC)….................10mA

Continuous Power Dissipation (T A = +70°C)

8-Pin SO (derate 5.9mW/°C above +70°C)..................471mW Operating Temperature Range (Note 1) ..........-55°C to +150°C Junction Temperature......................................................+150°C Storage Temperature Range.............................-65°C to +150°C Lead Temperature (soldering, 10s).................................+300°C

Note 1:The MAX6662 is not recommended to operate above +125°C for an extended period of time.

MAX6662

12-Bit + Sign Temperature Sensor with

SPI-Compatible Serial Interface

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-3

0-1-2123-503010-30-10507090110130150

TEMPERATURE ERROR VS. TEMPERATURE

TEMPERATURE (°C)

T E M P E R A T U R E E R R O R (°C

)

201040305060807090-0.45-0.35-0.25-0.150.050.150.250.350.45

TEMPERATURE ERROR DISTRIBTUTION

TEMPERATURE ERROR (°C)

P E R C E N T A G E O F S A M P L E S (%)

100

120

160

140

180200

SUPPLY CURRENT VS. TEMPERATURE

TEMPERATURE (°C)

S U P P L Y C U R R E N T (μA )

-50

50

100

150

Typical Operating Characteristics

(V CC = +3V, T A = +25°C, unless otherwise noted.)

ELECTRICAL CHARACTERISTICS (continued)

(V CC = +3V to +5.5V, T A = -55°C to +125°C, unless otherwise noted. Typical values are at T A = +25°C and V CC = +3.3V.)

M A X 6662

12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface 4_______________________________________________________________________________________

042

861012-50

50

100

150

SHUTDOWN CURRENT VS. TEMPERATURE

TEMPERATURE (°C)

S H U T D O W N C U R R E N T (μA )

Typical Operating Characteristics (continued)

(V CC = +3V, T A = +25°C, unless otherwise noted.)

Detailed Description

The MAX6662 continuously converts its die tempera-ture 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 SPI-compatible serial interface.

Figure 1 shows the simplified functional diagram of the MAX6662. Its internal current sources force 100μA and 10μA currents through a diode (diode-connected tran-sistor), 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 tempera-ture and the temperature limit settings stored in the reg-isters 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 sys-tem 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 (T LOW ) fault, as well as for an overtemperature (T HIGH ) fault. Once either fault has occurred, it remains active indefinitely, regard-less 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 corre-sponding to the fault (T LOW or T HIGH ) that initially set the ALERT .

MAX6662

12-Bit + Sign Temperature Sensor with

SPI-Compatible Serial Interface

_______________________________________________________________________________________

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For example: If T HIGH is set to 100°C and T HYST is set to 20°C, ALERT does not assert until temperature exceeds 100°C. If the temperature is then read through the serial interface, ALERT deasserts. ALERT asserts again when temperature is less than 80°C (Figure 2).Comparator Mode

In the comparator mode, ALERT is asserted when tem-perature exceeds the value in the T HIGH register, or is lower than the value in the T LOW register. ALERT deasserts when temperature is less than T HIGH - T HYST or greater than T LOW + T HYST . Reading the registers does not deassert ALERT .

For example: If T HIGH is set to 100°C and T LOW is set to 80°C, ALERT does not assert until temperature exceeds 100°C, or is below 80°C. Then, ALERT only deasserts if temperature is less than T HIGH - T HYST or greater than T LOW + T HYST .

Overtemperature Alert

OT operates only in comparator mode. The OT pin is asserted when the temperature exceeds T MAX , and deasserted when the temperature drops below T MAX - T HYST . A read operation does not reset OT . OT is an open-drain active-low (default) output, but can be programmed to active-high.

Figure 1. MAX6662 Simplified Functional Diagram

Figure 2. Example of ALERT Operation in Interrupt Mode

M A X 6662

12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface

Temperature Fault Queue

The activation of ALERT and OT is subject to the depth of the fault queue. I f the Fault Queue bit in the Configuration register is enabled, ALERT or OT does not assert until four consecutive temperature conver-sions are at fault.

For example: I f T HIGH is set to 100°C, T HYST is set to 20°C, ALERT is set to interrupt mode, and fault queue is enabled, ALERT does not assert until four consecu-tive conversions exceed 100°C. I f the temperature is then read through the serial interface, ALERT deasserts. ALERT asserts again when four consecutive conversions are less than 80°C.

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 seri-al interface. I n the shutdown mode, information stored in all registers is retained. The Temperature register retains the temperature from the last conversion result.

Serial Interface Protocol

The serial interface consists of three signal lines: chip select (CS ), bidirectional data line (SI O), and serial clock (SCLK). Only the master (external) drives CS and SCLK. Both the master and the MAX6662 drive SI O.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 mas-ter 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 MAX6662through the SIO. Sixteen cycles of data follow. The 16cycles of data are either driven by the master or by the MAX6662, depending on the command byte. I f the MAX6662 is driving the SI O, 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.

MAX6662

12-Bit + Sign Temperature Sensor with

SPI-Compatible Serial Interface

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The first bit of the command byte is always high to sig-nify 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 continu-ously 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 Registers

The MAX6662 has six registers: Temperature, Configura-tion, T HYST , T MAX , T LOW , and T HIGH 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 tempera-ture data for the most recent temperature conversion is

Figure 5. Bit Assignment for the MAX6662 Registers

stored in the Temperature register and is in °C, using a two ’s-complement format with 1LSB corresponding to 0.0625°C (Table 3). The three least-significant bits (LSBs)are temperature status (flag) bits. The Temperature regis-ter 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 (T LOW ), and the Hysteresis (T HYST ) registers set the temperature limit for triggering the ALERT (Figure 1).The Maximum-Temperature (T MAX ) and Hysteresis reg-isters 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 1°C 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.

Applications Information

The MAX6662 supply current is typically 125μA when the serial interface is active. When driving high-imped-ance loads, the devices dissipate negligible power;therefore, the die temperature is essentially the same as the package temperature. The key to accurate tem-perature monitoring is good thermal contact between the MAX6662 package and the monitored device or cir-cuit. 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:

?T J = P DISSIPATION x θJA

where P DISSIPATION is the power dissipated by the MAX6662, and θJA is the package ’s thermal resistance.The typical thermal resistance is +170°C/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 0.54°C rise in the die temperature.

Chip Information

TRANSISTOR COUNT:Bipolar: 182

MOS: 10177PROCESS: BiCMOS

M A X 6662

12-Bit + Sign Temperature Sensor with SPI-Compatible Serial Interface 8

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MAX6662

12-Bit + Sign Temperature Sensor with

SPI-Compatible Serial Interface

Maxim c annot assume responsibility for use of any c irc uitry other than c irc uitry entirely embodied in a Maxim produc t. No c irc uit patent lic enses 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?2001 Maxim Integrated Products

Printed USA

is a registered trademark of Maxim Integrated Products.

Package Information