Rev1.0 | Page 8/11

T06

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5.1 Operation at Very Slow I2C Bus Speeds

If the T06 is put to sleep with the sleep timer enabled, there will be one measurement done prior to sleep

with the settings as configured in the wake period (i.e., operate and release points). This measurement

starts at the falling edge of SCL prior to the ACK of the write that puts the part to sleep (i.e., writing 0x80 to

register 0xC4). When the measurement concludes, the output pin will be set high or low depending on the

measurement results, and the part will enter the sleep timer state.

In the sleep timer state, SDA will hold state until the next wake (either by host or due to the sleep timer,

which is typically 200 ms).Thus, it is important that the ACK concludes prior to entering the sleep state, or

SDA will hold low until the next wake. SDA is released at the falling edge of SCL, at the completion of the

ACK time. This takes 140 μs, and, therefore, the I2C clock speed must be fast enough that the time from

SCL falling prior to ACK to SCL falling after AC

K must be less than 140 μs. Depending on the host timing

for this portion of the I2C sequence, this corresponds to an I2C speed of greater than 7 KHz.

For very low I2C speeds, < 7KHz where this could be an issue, if the sleep timer function is not needed,

write the sleep bit of register 0xC4 to put the part to sleep. If the sleep timer is not running, there is no

measurement prior to sleep. SDA is released at the completion of the ACK, and the part will enter the

sleep state without the sleep timer running.

5.2 Measuring Temperature over I2C

The actual temperature of the device can be calculated by reading the Dspsigm and Dspsigl registers over I2C,

which correspond to the most significant and least significant bytes of the temperature measurements

respectively. The complete 15b unsigned result is 256

*Dspsigm[6:0]+Dspsigl[7:0].

A result of 16384 means the temperature is 55°C. More negative results mean lower temperature, and more

positive results mean higher temperature. Temperature is calculated from the formula:

T (°C) = 55+ (256*Dspsigm[6:0]+Dspsigl[7:0] -16384)/160

Read the register interface section for more details.