Case Temperature − C

°

0

20

40

60

80

100

120

140

160

180

0

50

100

150

200

ISO7420E, ISO7420FE

ISO7421E, ISO7421FE

www.ti.com

SLLSE45E – DECEMBER 2010 – REVISED JANUARY 2013

IEC 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

107

Safety input, output, or supply

mA

current

164

Maximum case 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 Characteristics 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.

PACKAGE THERMAL CHARACTERISTICS

(over recommended operating conditions unless otherwise noted)

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

212

Junction-to-air thermal resistance

°C/W

122

Junction-to-board thermal resistance

37

°C/W

Junction-to-case thermal resistance

69.1

°C/W

Device power dissipation

138

mW

Input a 100-Mbps 50% duty-cycle square wave

(1)

Tested in accordance with the low-K or high-K thermal metric definitions of EIA/JESD51-3 for leaded surface-mount packages

Figure 5.

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