8.2.2 TMP390-Q1 With 10°C Hysteresis

Figure 8-3 shows an example circuit for overtemperature and undertemperature protection using the TMP390-

Q1. In this example, the trip points are set at –25°C and +90°C with 10°C hysteresis.

TMP390-Q1

VDD

SETA

SETB

OUTA

OUTB

GND

Microprocessor

VCC

GND

78.7 kŸ

215 kŸ

10 kŸ

10 kŸ

0.1 µF

3.3 V

VDD = 3.0 V

Channel A Trip Temp = +90°C

and Hysteresis = 10°C

Channel B Trip Temp = ±25°C

and Hysteresis = 10°C

Figure 8-3. TMP390-Q1 Example Circuit at +90°C and –25°C Thresholds With 10°C Hysteresis

8.2.2.1 Design Requirements

In this example, VDD can be ≥ 3 V. The output pins may be tied to a switch to control a fan or other analog

circuitry. This example uses 10-kΩ pullup resistors at the OUTA and OUTB outputs. Place a 0.1-µF bypass

capacitor close to the TMP390-Q1 device to reduce noise coupled from the power supply. If needed, the output

of multiple parts can be connected together.

8.2.2.2 Detailed Design Procedure

SETA sets the +90°C threshold using 78.7 kΩ. SETB sets the –25°C trip point and 10°C hysteresis using 215

kΩ. These values were determined using Table 7-1 and Table 7-2. These resistors should have maximum of

1% tolerance and 100 ppm/°C or less over the desired temperature range. A summary of the resistor settings

used in this example is shown in Table 8-1. See Table 7-1 and Table 7-2 for additional trip points and hysteresis

configurations.

The switching output of the TMP390-Q1 can be visualized with the output diagram shown in Figure 8-4. It is

key to notice that hysteresis is subtracted from the Channel A threshold and added to the Channel B threshold

values. OUTA remains high until the sensor reaches +90°C where the output goes low, and returns high after the

temperature drops back down to +80°C. OUTB trips when the temperature stays below –25°C and goes low until

the temperature rises above –15°C.

Table 8-1. Example Resistor Settings and Trip Points

CHANNEL

RESISTOR SETTING (kΩ)

HYSTERESIS (°C)

TRIP TEMPERATURE (°C)

SETA

78.7

10

+90

SETB

215

–25

www.ti.com

TMP390-Q1

SNIS218B – SEPTEMBER 2019 – REVISED JUNE 2022

Copyright © 2022 Texas Instruments Incorporated

Submit Document Feedback

13

Product Folder Links: TMP390-Q1