HIiiiiii,
i am using TMP112 to monitor temperature change. I am using POL = 0 and TM = 1. After each read of the current temperature, the higher and lower threshold are set +1 and -1 of the current temperature. the interrupt is working fine with some glitches. if the temperature increases the higher threshold then an interrupt is receive but if the temperature decreases and crosses the lower threshold temperature set, interrupt is not generated..WHY???please help me out
Thanks in advace
Hello Sanjat,
When the TMP112 is in Interrupt mode (TM=1), the interrupt becomes active in a cyclical fashion as shown in Figure 13 below and as described in the section HIGH- AND LOW-LIMIT REGISTERS.
In order for an interrupt to occur, the part must first read a temperature equal to or greater than THIGH. Once the interrupt is cleared, it becomes active again only when temperature reads equal to or less than TLOW. Once this interrupt clears, the cycle repeats.
In summary, the ALERT pin becomes active in the following order: Temp ≥ THIGH, Temp ≤ TLOW, Temp ≥ THIGH, Temp ≤ TLOW, etc.
Best regards,
Ian Williams
Linear Applications Engineer
Precision Linear and Sensing Products
Sanjat,
The TMP112 does not support a continuous low interrupt, so that functionality is not possible with this device. This is true of all of the TI temperature sensors with an ALERT functionality.
However, what you want to accomplish is possible with a temperature switch such as the LM56: http://focus.ti.com/general/docs/nationalsemiconductorproducts.tsp?genericPartNumber=LM56. This device supports two resistor-programmable temperature thresholds T1 and T2. There are two corresponding outputs OUT1 and OUT2 which go high or low depending on whether the measured temperature is above or below each threshold. More specifically, OUT1 goes LOW when Temp > T1 and goes HIGH when Temp < T1 - 5°C. Similarly, OUT2 goes LOW when Temp > T2 and goes HIGH when Temp < T2 - 5°C. The output characteristic is also shown below.
Best regards,
Ian Williams
