ADE1201 datasheet(27/40 Pages) AD

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Data Sheet

ADE1201

Rev. 0 | Page 27 of 40

VERSION

The REVID bits (Bits[8:5]) in the CTRL register identify the

version of the IC.

INSULATION WEAR OUT

The lifetime of insulation caused by wear out is determined by

the isolation thickness, material properties, and the voltage

stress applied. It is important to verify that the product lifetime

is adequate at the application working voltage. The working

voltage supported by an isolator for wear out may not be the

same as the working voltage supported for tracking. The working

voltage applicable to tracking is specified in most standards.

Testing and modeling show that the primary driver of long term

degradation is displacement current in the polyimide insulation

causing incremental damage. The stress on the insulation can be

broken down into broad categories, such as dc stress, which

causes very little wear out because there is no displacement

current, and an ac component time varying voltage stress,

which causes wear out.

The ratings in certification documents are typically based on

60 Hz sinusoidal stress because this value reflects isolation from

the line voltage. However, many practical applications have

combinations of 60 Hz ac and dc across the barrier, as shown

in Equation 14. Because only the ac portion of the stress causes

wear out, the equation can be rearranged to solve for the ac rms

voltage, as shown in Equation 15. For insulation wear out with the

polyimide materials used in the ADE1201, the ac rms voltage

determines the product lifetime.

RMS

AC RMS

(14)

AC RMS

RMS

−

(15)

where:

VRMS is the total rms working voltage.

VAC RMS is the time varying portion of the working voltage.

VDC is the dc offset of the working voltage.

Calculation and Use of Parameters Example

The following example frequently arises in power conversion

applications. Assume that the line voltage on one side of the

isolation is 240 V ac rms and a 400 V dc bus voltage is present

on the other side of the isolation barrier. The isolator material is

polyimide. To establish the critical voltages in determining the

creepage, clearance, and lifetime of a device, see Figure 44 and

the following equations.

TIME

VAC RMS

VRMS

VDC

VPEAK

Figure 44. Critical Voltage Example

Calculate the working voltage across the barrier from Equation 16

with the following equations:

RMS

AC RMS

(16)

240

400

RMS

(17)

In this example, VRMS = 466 V.

This VRMS value is the working voltage used together with the

material group and pollution degree when looking up the

creepage required by a system standard.

To determine if the lifetime is adequate, obtain the time varying

portion of the working voltage. To obtain the ac rms voltage,

use Equation 18.

AC RMS

RMS

−

(18)

466

400

AC RMS

−

(19)

In this example, VAC RMS = 240 V rms.

In this case, the ac rms voltage is simply the line voltage of

240 V rms. This calculation is more relevant when the waveform is

not sinusoidal. The value is compared to the limits for working

voltage in Table 12 for the expected lifetime, is less than a 60 Hz

sine wave, and is well within the limit for a 50-year service life.

Note that the dc working voltage limit in Table 12 is set by the

creepage of the package as specified in IEC 60664-1. This value

can differ for specific system level standards.

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