8 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

8.1 Applications Information

The TMP390 device is part of a family of ultra-low power, dual channel, resistor programmable temperature

switches that can enable detection and protection of system thermal events over a wide temperature range. The

trip temperatures (TTRIP) and hysteresis options are programmed by two E96-series (1%) standard decade value

resistors on the SETA and SETB pins. The thermal hysteresis (THYST) function is to prevent undesired digital

output switching due to small temperature changes.

8.2 Typical Applications

8.2.1 Simplified Application Schematic

Figure 8-1 shows the simplified schematic where RSETA and RSETB are used to set channel A trip point (SETA)

and channel B trip point and hysteresis for both channels (SETB). SETA and SETB can be programmed at a

variety of temperatures based on the device, as described in Table 7-1 for channel A trip point, and Table 7-2 for

channel B trip point and hysteresis for both channels. OUTA and OUTB outputs correspond to the temperature

threshold detection at SETA and SETB, respectively.

RSETA

RSETB

VDD

VDD or VDDIO

TMP39x

RP

RP

SETA

SETB

OUTA

OUTB

Optional Trip

Test

RSETA and RSETB select trip

thresholds and hysteresis options.

Figure 8-1. Simplified Schematic

8.2.1.1 Design Requirements

The TMP390 requires two resistors to set the high and low trip points and hysteresis, and two pullup resistors for

the open-drain device. TI also highly recommends to place a 0.1-µF, power-supply bypassing capacitor close to

the VDD supply pin. To minimize the internal power dissipation, use two pullup resistors greater than 1 kΩ from

the OUTA and OUTB pins to the VDD pin. A separate supply, VDDIO, may be used for the pullup voltage to set

the output voltage level to the level required by the MCU, as shown in Figure 8-1. The open-drain output gives

flexibility of pulling up to any voltage independent of VDD (VDDIO must be less than or equal to VDD + 0.3 V).

This allows for use of longer cables or different power supply options. If a separate voltage level is not required,

TI recommends to tie the pullup to the TMP390 VDD.

If the SETA or SETB connected resistor value is outside the legal range, the associated output goes to

permanent output zero stage and the channel cannot be used. The other channel still will be in operating

condition, and device can be used in one channel mode. If the SETB input is grounded or left floating, the

Channel B cannot be used and the hysteresis for Channel A will be 20°C. The SETA and SETB connected

resistors are measured during POR. If two consecutive measurements are not matching each other, then

the device sets the associated channel output to zero and repeats the resistor measurements until the

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TMP390

SBOS904A – MAY 2019 – REVISED AUGUST 2020

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