TMP9R01DGSSLASHEM datasheet(33/45 Pages) TI2

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TERR= 1.004−1.008

1.008 ×(273.15+100∘C)TERR= −1.48∘C

(5)

If a discrete transistor is used as the remote temperature sensor with the TMP9R01-SEP and TMP9R01-SP

devices, the best accuracy can be achieved by selecting the transistor according to the following criteria:

1. Base-emitter voltage is > 0.25V at 7.5μA, at the highest-sensed temperature.

2. Base-emitter voltage is < 0.95V at 120μA, at the lowest-sensed temperature.

3. Base resistance is < 100Ω.

4. Tight control of VBE characteristics indicated by small variations in hFE (that is, 50 to 150).

Based on this criteria, two recommended small-signal transistors are the 2N3904 (NPN) or 2N3906 (PNP).

9.2.2 Detailed Design Procedure

The local temperature sensor inside the TMP9R01-SEP and TMP9R01-SP devices monitor the ambient air

around the device. The thermal time constant for the device is approximately 1.1 seconds. This constant implies

that if the ambient air changes quickly by 100°C, then the device takes approximately 5.5 seconds (that is, five

thermal time constants) to settle to within 1°C of the final value. In most applications, the TMP9R01-SEP and

TMP9R01-SP package is in electrical, and therefore thermal, contact with the printed circuit board (PCB), as well

as subjected to forced airflow. The accuracy of the measured temperature directly depends on how accurately

the PCB and forced airflow temperatures represent the temperature that the device is measuring. Additionally,

the internal power dissipation of the device can cause the temperature to rise above the ambient or PCB

temperature. The internal power dissipated as a result of exciting the remote temperature sensor is negligible

because of the small currents used. Equation 6 can be used to calculate the average conversion current for

power dissipation and self-heating based on the number of conversions per second and the temperature sensor

channel enabled. Typical Application shows an example with local and remote sensor channels enabled and

16 conversions per second; see the Section 6.5 table for typical values required for these calculations. For a

3.3V supply and a conversion rate of 16 conversions per second, the TMP9R01-SEP and TMP9R01-SP devices

dissipates 0.531mW (PDIQ = 3.3V × 161μA) when both the remote and local channels are enabled.

Average Conversion Current

Local ADC Conversion Time

Conversions per Second

Local Active I

Remote ADC Conversion Time

Conversions per Second

Remote Active I

Standby Mode I

Local ADC Conversion Ti

Remote ADC Conversion Time

Conversions per Second

(6)

Average Conversion Current=(15ms) 16s ×(240μA)

(7)

+(15ms)× 16s(400μA)

(8)

+(15μA)× 1−(15ms+15ms)× 16s

(9)

=161μA

(10)

The temperature measurement accuracy of the device depends on the remote and local temperature sensor

being at the same temperature as the system point being monitored. If the temperature sensor is not in good

thermal contact with the part of the system being monitored, then there is a delay between the sensor response

and the system changing temperature. This delay is typically not a concern for remote temperature-sensing

applications that use a substrate transistor (or a small, SOT23 transistor) placed close to the device being

monitored.

9.2.3 Application Curve

Figure 9-3 shows the step response of the TMP9R01-SEP and TMP9R01-SP devices to a submersion in an

oil bath of 100°C from room temperature (25°C). The time-constant, or the time for the output to reach 63% of

the input step, is around 1.1s for local sensors and 0.6s for the remote diode sensor. The time-constant result

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TMP9R01-SEP, TMP9R01-SP

SNIS238A – JULY 2025 – REVISED JULY 2026

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