Datasheet ADT7422 (Analog Devices) - 10

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ADT7422 Data Sheet CT and INT Operation in One Shot Mode
conversions are initiated until the ADT7422 is taken out of See Figure 14 for more information on one shot mode CT pin shutdown mode. To take the ADT7422 out of shutdown mode, operation for T write 0 to Bit 6 and Bit 5 in the configuration register (Register CRIT overtemperature events when one of the limits is exceeded. Note that in interrupt mode, a read from any Address 0x03). The ADT7422 typically takes 1 ms (with a 0.1 μF register resets the INT pin and CT pin. decoupling capacitor) to exit shutdown mode. The conversion result from the last conversion prior to shutdown can still be In comparator mode, if the temperature drops below THIGH − THYST read from the ADT7422 when the device is in shutdown mode. or goes above TLOW + THYST, a write to the operation mode bits When the device is taken out of shutdown mode, the internal (Register Address 0x03, Bits[6:5]) resets the INT pin. clock starts and a conversion is initiated. In comparator mode, if the temperature drops below TCRIT − THYST,
FAULT QUEUE
a write to the operation mode bits (Register Address 0x03, Bits[6:5]) resets the CT pin (see Figure 14). Bit 0 and Bit 1 of the configuration register (Register Address 0x03) are used to set up a fault queue. The queue can facilitate up to four When using one shot mode, ensure that the appropriate refresh fault events to prevent false tripping of the INT pin and CT pin rate is used for the given application. when the ADT7422 is used in a noisy temperature environment.
1 SPS MODE
The number of faults set in the queue must occur consecutively In 1 SPS mode, the device performs one measurement per second. to set the INT and CT outputs. For example, if the number of A conversion typically takes 60 ms and the device remains in the faults set in the queue is four, four consecutive temperature idle state for the remaining 940 ms period. To enable 1 SPS mode, conversions must occur with each result exceeding a temperature write 1 to Bit 6 and 0 to Bit 5 of the configuration register limit in any of the limit registers before the INT pin and CT pin (Register Address 0x03). are activated. If two consecutive temperature conversions exceed a temperature limit and the third conversion does not, the fault
SHUTDOWN MODE
count is reset back to zero. To place the ADT7422 in shutdown mode, write 1 to Bit 6 and Bit 5 of the configuration register (Register Address 0x03), in which case the entire IC is shut down and no further
TEMPERATURE 149°C 148°C 147°C TCRIT 146°C 145°C 144°C 143°C 142°C TCRIT – THYST 141°C 140°C CT PIN POLARITY = ACTIVE LOW CT PIN POLARITY = ACTIVE HIGH TIME WRITE TO WRITE TO WRITE TO BIT 5 AND BIT 6 OF BIT 5 AND BIT 6 OF BIT 5 AND BIT 6 OF CONFIGURATION CONFIGURATION CONFIGURATION REGISTER.* REGISTER.* REGISTER.* *THERE IS A 240ms DELAY BETWEEN WRITING TO THE CONFIGURATION REGISTER TO START
011
A STANDARD ONE SHOT CONVERSION AND TO ACTIVATE THE CT PIN DUE TO THE DELAY IS
61-
60ms IN THE CASE OF A ONE SHOT CONVERSION.
209 Figure 14. One Shot CT Pin Rev. 0 | Page 10 of 23 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION PRODUCT HIGHLIGHTS FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS I2C TIMING SPECIFICATIONS Timing Diagram ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION CIRCUIT INFORMATION CONVERTER DETAILS NORMAL MODE ONE SHOT MODE CT and INT Operation in One Shot Mode 1 SPS MODE SHUTDOWN MODE FAULT QUEUE TEMPERATURE DATA FORMAT TEMPERATURE CONVERSION FORMULAS 16-Bit Temperature Data Format 13-Bit Temperature Data Format 10-Bit Temperature Data Format 9-Bit Temperature Data Format REGISTERS ADDRESS POINTER REGISTER TEMPERATURE VALUE REGISTERS STATUS REGISTER CONFIGURATION REGISTER THIGH SETPOINT REGISTERS TLOW SETPOINT REGISTERS TCRIT SETPOINT REGISTERS THYST SETPOINT REGISTER ID REGISTER SERIAL INTERFACE SERIAL BUS ADDRESS WRITING DATA READING DATA RESET GENERAL CALL INT AND CT OUTPUTS UNDERTEMPERATURE AND OVERTEMPERATURE DETECTION Comparator Mode Interrupt Mode APPLICATIONS INFORMATION THERMAL RESPONSE TIME SUPPLY DECOUPLING POWERING FROM A SWITCHING REGULATOR TEMPERATURE MEASUREMENT QUICK GUIDE TO MEASURING TEMPERATURE OUTLINE DIMENSIONS ORDERING GUIDE