TMP275: if it possible to drive mosfet directly from ALERT pin

Hi Shai,
As you may notice form the data sheet the ALERT pin is a open drain output so it requires a pull up. Therefore the a ser depends if your mosfet will have the same VCC as the TMP device. If it’s quite higher e.g. 12V than it won’t work since the internal ESD structure of the TMP device will trigger first.

Hi Shai,

ALERT pin is capable of sinking 4mA to GND. You would still need to provide a pull-up resistor to V+ (or other voltage which does not exceed 7V Absolute Max Rating.) The ALERT pin will idle at the pull-up voltage and pull-down to 0V to indicate ALERT.

A small signal MOSFET whose gate meets these voltage and current requirements should work. Keep in mind the output polarity might be inverted depending on your circuit.

Thanks,
Ren

Hi Shai,

The ALERT pin can be configured for Comparator mode (TM=0 in Config Register.) This is most likely the mode that you want. The ALERT pin will idle at high impedance (logic high is created by pull-up resistor.) When temperature exceeds the value in High Limit Register 0x03, the ALERT pin will sink current to create logic low. This is 0V referenced to TMP275's GND pin. The ALERT pin will remain at logic low until temperature falls below the value in Low Limit Register 0x02. The polarity of ALERT can be inverted by setting POL=1 in the Config Register. See Figure 15 on page 17 of the datasheet.

The ALERT pin can drive other logic inputs given the constraints in the datasheet that are summarized in my previous post.

Thanks,
Ren