5.12 Safety Limiting Values

Safety limiting intends to prevent potential damage to the isolation barrier upon failure of input or output circuitry.

A failure of the I/O can allow low resistance to ground or the supply and, without current limiting, dissipate

sufficient power to overheat the die and damage the isolation barrier potentially leading to secondary system

failures.

Table 5-5. Safety Limiting

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

IS

Safety input, output, or supply

current for DW-16 package

and DWW-16 Packages

RθJA = 84.7°C/W, VI = 5.5 V, TJ = 150°C, TA = 25°C

268

mA

RθJA = 84.7°C/W, VI = 3.6 V, TJ = 150°C, TA = 25°C

410

RθJA = 84.7°C/W, VI = 2.75 V, TJ = 150°C, TA = 25°C

537

PS

Safety input, output, or total

power

RθJA = 84.7°C/W, TJ = 150°C, TA = 25°C

1476

mW

TS

Maximum safety temperature

150

°C

The maximum safety temperature is the maximum junction temperature specified for the device. The power

dissipation and junction-to-air thermal impedance of the device installed in the application hardware determines

the junction temperature. The assumed junction-to-air thermal resistance in the Section 5.4 is that of a device

installed on a High-K test board for Leaded Surface Mount Packages. The power is the recommended maximum

input voltage times the current. The junction temperature is then the ambient temperature plus the power times

the junction-to-air thermal resistance.

Ambient Temperature (qC)

0

50

100

150

200

0

100

200

300

400

500

600

D014

VCC1 = VCC2 = 2.75 V

VCC1 = VCC2 = 3.6 V

VCC1 = VCC2 = 5.5 V

Figure 5-1. Thermal Derating Curve for Safety

Limiting Current per VDE

Ambient Temperature (qC)

0

50

100

150

200

0

200

400

600

800

1000

1200

1400

1600

D015

Power

Figure 5-2. Thermal Derating Curve for Safety

Limiting Power per VDE

ISO7821, ISO7821F

SLLSEM2H – NOVEMBER 2014 – REVISED NOVEMBER 2024

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