• When selecting ferrite beads for high-frequency filtering, ensure DCR < 1Ω to avoid voltage drops that could

introduce additional noise on VDD.

• Use low-ESR capacitors, which provide a low-impedance path to ground and improve high-frequency noise

suppression.

7.1.3.3 PCB Layout Practices

PCB layout also plays a key role in EMI performance:

• Route ISOTMP35R signal traces away from high-voltage noise sources.

• Avoid wrapping traces around noisy components, which increases noise coupling.

• Where possible, route signal traces between quiet GND planes on two layers, using stitching vias to connect

the planes. This provides a low-impedance return path for noise, reducing its effect on the signal.

By combining robust filtering with careful PCB layout, designers can significantly reduce EMI impact and ensure

accurate temperature measurements.

7.1.4 Insulation Lifetime

Insulation lifetime projection data is collected by using the industry-standard time-dependent dielectric

breakdown (TDDB) test method. In this test, all pins on each side of the barrier are tied together, creating a

two-terminal device, and high voltage is applied between the two sides. See Figure 7-4 for TDDB test setup. The

insulation breakdown data is collected at various high voltages, switching at 60Hz over temperature.

DUT

V

S

Time Counter

>1mA

A

Oven at 150°C

Figure 7-4. Test Setup for Insulation Lifetime Measurement

7.2 Power Supply Recommendations

To maintain stable operation, a 0.1µF ceramic bypass capacitor is recommended at the VDD supply pin.

This capacitor can be placed as close as possible to the device to provide effective noise decoupling. The

ISOTMP35R device operates from a single-supply configuration and does not require an isolated power source.

7.2.1 PSRR Considerations

Depending on the application, there can be a significant amount of high-frequency noise on the power supply

line. If high-frequency noise (>100kHz) is present, the user can switch to a 1μF bypass capacitor to provide

additional filtering on the power supply line. Increasing the bypass capacitance or choosing a capacitor with a

lower ESR across frequency improves PSRR performance.

An additional power supply consideration is line regulation. For the ISOTMP35R device, line regulation refers

to the change in output temperature with changing power supply. Figure 5-6 shows that, across the entire

environment temperature range, ISOTMP35R maintains a steady amount change in temperature across VDD.

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ISOTMP35R

SNIS244 – SEPTEMBER 2025

Copyright © 2025 Texas Instruments Incorporated

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