Case Temperature − C

°

0

20

40

60

80

100

120

140

160

180

0

50

100

150

200

G002

ISO7420, ISO7420M, ISO7421

SLLS984I – JUNE 2009 – REVISED JULY 2015

www.ti.com

SPACER

NOTE

Creepage and clearance requirements should be applied according to the specific

equipment isolation standards of an application. Care should be taken to maintain the

creepage and clearance distance of a board design to ensure that the mounting pads of

the isolator on the printed-circuit board do not reduce this distance.

Creepage and clearance on a printed-circuit board become equal in certain cases.

Techniques such as inserting grooves and/or ribs on a printed circuit board are used to

help increase these specifications.

8.3.3 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.

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

112

Safety input, output, or supply

mA

current

171

Maximum safety temperature

150

°C

The safety-limiting constraint is the absolute-maximum junction temperature specified in the Absolute Maximum

Ratings table. 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

Thermal Information table is that of a device installed in the JESD51-3, Low-Effective-Thermal-Conductivity Test

Board for Leaded Surface-Mount Packages and is conservative. 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.

Figure 10.

16

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