7 Detailed Description

7.1 Overview

The TMP390 ultra-low power, dual channel, resistor programmable temperature switches enable detection

and protection of system thermal events over a wide temperature range. The TMP390 offers independent

overtemperature (hot) and undertemperature (cold) detection. The trip temperatures and hysteresis options

are programmed by two E96-series (1%) standard decade value resistors on the SETA and SETB pins. The

TMP390 can enable a customer board-level manufacturing test through the trip test function that can force the

SETA or SETB pins to logic high to activates the digital outputs.

7.2 Functional Block Diagram

RSETA

RSETB

VDD

VDD or VDDIO

RP

RP

SETA

SETB

OUTB

RSETA and RSETB select trip

thresholds and hysteresis options.

TMP39x

C

OUTA

Figure 7-1. Simplified Schematic

7.3 Feature Description

The TMP390 requires two resistors to set the two trip points and hysteresis, according to Table 7-1 and Table

7-2, for the hot and cold channel device. The output of the TMP390 is open-drain and requires two pullup

resistors. TI recommends to use a pullup voltage supply that does not exceed VDD + 0.3 V. The pullup resistors

used in between the OUTA and OUTB pins and the pullup supply should be greater than 1 kΩ. The device

powers on when the supply voltage goes beyond 1.5 V, and starts sampling the input resistors to set the two

trip points and hysteresis value after power-on. These values will remain the same until the device goes through

a power cycle. After the device sets the trip points and hysteresis level, the device will update the output every

half a second. The conversion time is typically 0.65 ms when the temperature is checked against the trip points

and the outputs are updated. The device remains in standby mode between conversions. If either channel is not

used, the output can be grounded or left floating.

7.3.1 TMP390 Programming Tables

The temperature threshold and hysteresis options for the TMP390 device are programmed using two external

1% E96 standard resistors. The specific resistor value to ground on the SETA input sets the temperature

threshold of channel A. The specific resistor value to ground on the SETB input sets the temperature threshold

of channel B, as well as the hysteresis for both channel A and channel B.

Table 7-1. TMP390 Channel A Threshold Setting

CHANNEL A (HOT)

TRIP TEMPERATURE

(°C)

CHANNEL A NOMINAL 1%

RESISTORS (KΩ)

CHANNEL A (HOT) TRIP

RESET TEMPERATURE (°C) FOR

HYSTERESIS = 5°C

CHANNEL A (HOT) TRIP

RESET TEMPERATURE (°C) FOR

HYSTERESIS = 10°C

30

1.05

25

20

32

1.21

27

22

34

1.40

29

24

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TMP390

SBOS904A – MAY 2019 – REVISED AUGUST 2020

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