7.3.3.2.1 Comparison to NTC Thermistors

Comparison to NTC thermistors highlights the benefit of direct thermal coupling enabled by the ISOTMP35R .

In this test, heat is applied through a high-voltage copper plane connected to the TSENSE pins, while the

low-voltage side remains at 25°C. A temperature step of 100°C (25°C to 125°C) is applied at the heat source.

This condition represents applications where the temperature of interest is localized at the heat source rather

than uniformly distributed across the package.

Figure 7-9 shows the test configurations for the ISOTMP35R and discrete NTC implementations. The

ISOTMP35R is thermally coupled directly to the heat source through the TSENSE pins. In contrast, the NTC

thermistors are positioned approximately 8mm away and rely on heat transfer through PCB material and, in one

configuration, a thermal conductive epoxy.

T = TA = 25°C

Additional thermal

gradient from lower

temperature side

T = TTEST

Heat sourced

through 2oz.

Copper plane

HIGH

VOLTAGE

HV

FR-4 PCB

LV

T = TTEST

Heat sourced

through 2oz.

Copper plane

HIGH

VOLTAGE

HV

FR-4 PCB

LV

MCU/ADC

NTC

HE

Figure 7-9. Test Setup: ISOTMP35R vs NTC

Figure 7-10 shows the measured thermal response of the ISOTMP35R compared to two NTC configurations:

with and without thermal epoxy.

Figure 7-10. Thermal Response Comparison

As summarized in Table 7-2, the ISOTMP35R reaches the final temperature significantly faster and remains

closer to the 125°C reference during the transient response. This behavior results from the direct thermal

coupling through the TSENSE pins, which minimizes thermal resistance between the heat source and the

sensing element.

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ISOTMP35R

SNIS244A – SEPTEMBER 2025 – REVISED MAY 2026

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