ADUM3472WCRSZ-RL7 View Datasheet(PDF) - Analog Devices

Part Name

Description

MFG CO.

ADUM3472WCRSZ-RL7

PWM Controller and Transformer Driver with Quad-Channel Isolators

Analog Devices 

Data Sheet

ADuM3470/ADuM3471/ADuM3472/ADuM3473/ADuM3474

Because the rate of charge of the secondary side is dependent

on the soft start cycle, loading conditions, input voltage, and

output voltage level selected, care should be taken in the design

to allow the converter to stabilize before valid data is required.

When power is removed from VDD1, the primary side converter

and coupler shut down when the UVLO level is reached. The

secondary side stops receiving power and starts to discharge.

The outputs on the secondary side hold the last state that they

received from the primary side until either the UVLO level is

reached and the outputs are placed in their default low state,

or the outputs detect a lack of activity from the inputs and the

outputs are set to their default value before the secondary power

reaches UVLO.

INSULATION LIFETIME

All insulation structures eventually break down when subjected

to voltage stress over a sufficiently long period. The rate of insu-

lation degradation is dependent on the characteristics of the voltage

waveform applied across the insulation. Analog Devices conducts

an extensive set of evaluations to determine the lifetime of the

insulation structure within the ADuM347x devices.

Accelerated life testing is performed using voltage levels higher

than the rated continuous working voltage. Acceleration factors

for several operating conditions are determined, allowing calcu-

lation of the time to failure at the working voltage of interest.

The values shown in Table 11 summarize the peak voltages for

50 years of service life in several operating conditions. In many

cases, the working voltage approved by agency testing is higher

than the 50-year service life voltage. Operation at working

voltages higher than the service life voltage listed in Table 11

leads to premature insulation failure.

The insulation lifetime of the ADuM347x depends on the voltage

waveform type imposed across the isolation barrier. The iCoupler

insulation structure degrades at different rates, depending on

whether the waveform is bipolar ac, dc, or unipolar ac. Figure 46,

Figure 47, and Figure 48 illustrate these different isolation

voltage waveforms.

Bipolar ac voltage is the most stringent environment. A 50-year

operating lifetime under the bipolar ac condition determines the

maximum working voltage recommended by Analog Devices.

In the case of unipolar ac or dc voltage, the stress on the insulation

is significantly lower. This allows operation at higher working

voltages while still achieving a 50-year service life. The working

voltages listed in Table 11 can be applied while maintaining the

50-year minimum lifetime, provided that the voltage conforms

to either the unipolar ac or dc voltage cases. Treat any cross-

insulation voltage waveform that does not conform to Figure 47

or Figure 48 as a bipolar ac waveform, and limit its peak voltage

to the 50-year lifetime voltage value listed in Table 11.

The voltage presented in Figure 48 is shown as sinusoidal for

illustration purposes only. It is meant to represent any voltage

waveform varying between 0 V and some limiting value. The

limiting value can be positive or negative, but the voltage cannot

cross 0 V.

RATED PEAK VOLTAGE

0V

Figure 46. Bipolar AC Waveform

RATED PEAK VOLTAGE

0V

Figure 47. DC Waveform

RATED PEAK VOLTAGE

0V

Figure 48. Unipolar AC Waveform

Rev. B | Page 31 of 36

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