ISO7740 datasheet(12/52 Pages) TI2

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5.8 Safety Limiting Values

Safety limiting(1) intends to minimize 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.

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

DW-16 PACKAGE

Safety input, output, or supply current

RθJA =83.4°C/W, VI = 5.5 V, TJ = 150°C,

TA = 25°C, see Figure 5-1

273

RθJA = 83.4°C/W, VI = 3.6 V, TJ = 150°C,

TA = 25°C, see Figure 5-1

416

RθJA = 83.4°C/W, VI = 2.75 V, TJ = 150°C,

TA = 25°C, see Figure 5-1

545

Safety input, output, or total power

RθJA = 83.4°C/W, TJ = 150°C, TA = 25°C,

see Figure 5-3

1499

Maximum safety temperature

150

°C

DBQ-16 PACKAGE

Safety input, output, or supply current

RθJA =109°C/W, VI = 5.5 V, TJ = 150°C,

TA = 25°C, see Figure 5-2

209

RθJA = 109°C/W, VI = 3.6 V, TJ = 150°C,

TA = 25°C, see Figure 5-2

319

RθJA = 109°C/W, VI = 2.75 V, TJ = 150°C,

TA = 25°C, see Figure 5-2

417

Safety input, output, or total power

RθJA = 109°C/W, TJ = 150°C, TA = 25°C,

see Figure 5-4

1147

Maximum safety temperature

150

°C

(1)

The maximum safety temperature, TS, has the same value as the maximum junction temperature, TJ, specified for the device. The

IS and PS parameters represent the safety current and safety power respectively. The maximum limits of IS and PS should not be

exceeded. These limits vary with the ambient temperature, TA.

The junction-to-air thermal resistance, RθJA, in the table above is that of a device installed on a high-K test board for leaded

surface-mount packages. Use these equations to calculate the value for each parameter:

TJ = TA + RθJA × P, where P is the power dissipated in the device.

TJ(max) = TS = TA + RθJA × PS, where TJ(max) is the maximum allowed junction temperature.

PS = IS × VI, where VI is the maximum input voltage.

ISO7740, ISO7741, ISO7742

SLLSEP4J – MARCH 2016 – REVISED OCTOBER 2024

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