SN65HVD61

www.ti.com

SLLS770D

– JANUARY 2007 – REVISED JUNE 2011

APPLICATION INFORMATION

THERMAL SHUTDOWN

In most cases, the device

’s internal junction temperature will not reach the thermal shutdown temperature if

operated within the recommended operating conditions. However, during fault conditions, such as driver

short-circuit, the junction temperature may reach the thermal shutdown limit. This also depends on the thermal

characteristics of the device mounting, the circuit board, and environmental factors. After the device reaches the

thermal shutdown temperature, the driver outputs will be disabled, and the device will cool down. If the

short-circuit is still present when the drivers are re-enabled, this thermal shutdown cycle will repeat until the

short-circuit fault is removed.

For long-term reliability, the package power dissipation must not exceed the values in the data sheet POWER

DISSIPATION RATINGS for extended periods.

POWER-UP TRANSIENTS

The absolute maximum ratings for Vcc and Vdd specify the limits for these supplies. During initial power-on,

these supply voltages may instantaneously drop below the given lower limit. Designers should consider that

diodes in the circuitry will begin to turn on if the voltage becomes too negative, and that damage may occur if

these diodes dissipate significant power internal to the device. The actual threshold for possible damage is a

function of both undervoltage magnitude and undervoltage transient duration. Further, the allowable undervoltage

transient conditions depend on factors such as device junction temperature and power supply source impedance.

THERMAL CHARACTERISTICS OF IC PACKAGES

Junction-to-Ambient Thermal Resistance (

temperature divided by the operating power.

•

the PCB design (50% variation)

•

altitude (20% variation)

•

device power (5% variation)

used. Standardized testing includes specification of PCB construction, test chamber volume, sensor locations,

and the thermal characteristics of holding fixtures.

temperatures for other installations.

TI uses two test PCBs as defined by JEDEC specifications. The low-k board gives average in-use condition

thermal performance and consists of a single trace layer 25 mm long and 2-oz thick copper. The high-k board

gives best case in-use condition and consists of 2 1-oz buried power planes with a single trace layer 25 mm long

with 2-oz thick copper. A 4% to 50% difference in

Junction-to-case thermal resistance (

operating power. It is measured by putting the mounted package up against a copper block cold plate to force

heat to flow from die, through the mold compound into the copper block.

predict junction temperature as it provides pessimistic numbers if the case temperature is measured in a

non-standard system and junction temperatures are backed out. It can be used with

simulation of a package system.

Junction-to-board thermal resistance (

PCB temperature at the center of the package (closest to the die) when the PCB is clamped in a cold

−plate

structure.

Copyright

© 2007–2011, Texas Instruments Incorporated

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