Texas Instruments recommends a 2-layer or 4-layer PCB with a solid ground plane and a thermal relief pattern around the device to ensure optimal thermal performance. A detailed layout guide can be found in the application note 'LM99 Thermal Layout Guidelines' (SLUA271).
To ensure accurate temperature measurement, it is essential to calibrate the device using the CAL pin. The calibration process involves shorting the CAL pin to VCC or GND to set the internal reference voltage. Additionally, the device should be operated within the recommended temperature range, and the thermal sensing element should be placed close to the device being monitored.
The maximum cable length for the remote temperature sensing diode is dependent on the cable capacitance and the desired accuracy. As a general guideline, Texas Instruments recommends keeping the cable length below 10 inches (25 cm) to ensure accurate temperature measurement. For longer cable lengths, it is recommended to use a shielded cable and to add a 100-ohm resistor in series with the diode to reduce noise and capacitance effects.
Yes, the LM99 can be used with a microcontroller that has a 3.3V supply. The device is compatible with 3.3V and 5V logic levels, and the output voltage can be adjusted using the VOUT pin. However, it is essential to ensure that the microcontroller can handle the output current of the LM99, which is typically around 10mA.
The LM99 has a built-in power-on reset (POR) circuit that ensures the device is in a known state after power-up. The POR circuit can be bypassed by connecting the POR pin to VCC or GND. However, it is recommended to use the POR pin to ensure proper device operation and to prevent any potential issues during power-up.
LM99CIMMX/NOPB datasheet
by Texas Instruments
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