An RC filter placed near the ADC input, consisting of RFLT_2 and CFLT_2, is recommended to attenuate high-

frequency noise and to isolate the sensor output from ADC sampling transients. This stage represents the

primary signal-conditioning filter for most applications.

Additional filtering stages, such as CFLT_1 and RFLT_1, can be used to further attenuate noise in systems with

long routing distances or elevated electromagnetic interference. These stages are applied only as needed,

based on system-level evaluation. Optional ferrite beads can be inserted in the signal path or supply path to

suppress high-frequency interference. RFLT_3 is only required when the optional ferrite bead is populated, where

it provides damping between the ferrite bead and downstream capacitance to suppress resonance and maintain

stable filter behavior.

On the supply path, a local bypass capacitor (CBYPASS) must always be placed close to the VDD pin. Additional

filtering using a ferrite bead and capacitor (CFLT_3) can be used to reduce conducted noise on the supply line.

Only the capacitance directly connected to VOUT contributes to the effective load seen by the output stage.

Capacitance located downstream of RISO does not affect output stability.

The component values used in Figure 8-3 provide a recommended starting point; however, the final values

depend on system-level conditions, including noise spectrum, ADC characteristics, and PCB layout, and must be

validated during system design.

8.1.6 Insulation Lifetime

The insulation lifetime of the ISOTMP35R is characterized using the industry-standard time-dependent dielectric

breakdown (TDDB) method.

In this test, all pins on each side of the isolation barrier are tied together to form a two-terminal structure. A high

voltage is applied across the barrier while monitoring for dielectric breakdown over time. Testing is performed

across multiple voltage levels and temperatures with an applied AC voltage at 60Hz. The measured data is used

to model the long-term behavior of the isolation barrier and to define the allowable operating conditions.

Figure 8-4 shows the TDDB lifetime projection. The red line represents the fitted TDDB model corresponding

to a failure rate of less than 1 defect per million (1 DPPM). The shaded region indicates the recommended

operating region of the device.

At a working isolation voltage of 1060VRMS and a junction temperature of 150°C, the projected insulation lifetime

exceeds 15 years. Operation within the specified isolation ratings maintains the projected insulation lifetime.

0

1000

2000

3000

4000

5000

6000

7000

8000

Applied Voltage (V

RMS)

1E+01

1E+02

1E+03

1E+04

1E+05

1E+06

1E+07

1E+08

1E+09

1E+10

1E+11

1E+12

T

A= 150°C, Working Isolation Voltage = 1060VRMS, Applied Voltage Frequency = 60Hz,

Projected Insulation Lifetime ≥ 15 years

Operating Zone

TDDB Line

(< 1DPPM Fail Rate)

~15 Years

Figure 8-4. Isolation Lifetime Projection

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ISOTMP35R

SNIS244A – SEPTEMBER 2025 – REVISED MAY 2026

Copyright © 2026 Texas Instruments Incorporated

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