Ambient Temperature (qC)

-55

-35

-15

5

25

45

65

85

105

125

10

15

20

25

30

35

D012

21

TMCS1100

www.ti.com

SBOS820 – SEPTEMBER 2019

Product Folder Links: TMCS1100

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Copyright © 2019, Texas Instruments Incorporated

10.1.2 Safe Operating Area

The isolated input current safe operating area (SOA) of the TMCS1100 is constrained by input conductor thermal

capability refers to the ability of the device to conduct a given dc or rms current (if a periodic or ac waveform)

continuously through the device at a given ambient temperature. The TMCS1100 can tolerate much higher

transient short-duration currents, which are limited by different thermal mechanisms, such as fusing of the

leadframe. These mechanisms depend on pulse duration, amplitude, and device thermal states.

Current capability for both rms and short-duration pulses depend on the thermal environment and design of the

system-level board. All thermal and SOA ratings are for a single TMCS1100 device on the TMCS1100EVM, with

no air flow in the specified ambient temperature conditions. Device use profiles must satisfy both continuous

conduction and short-duration transient SOA capabilities for the thermal environment under which the system will

be operated.

10.1.2.1 Continuous-Current Capability

The continuous-current capability of the TMCS1100 is constrained by the maximum junction temperature

because of the power dissipation in the input conductor and die. Multiple thermal variables control the transfer of

heat from the device to the surrounding environment, including air flow, ambient temperature, and PCB

construction and design. The longest thermal time constants of the device packaging and board are on the order

of seconds; therefore, any continuous periodic waveform with a frequency higher than 1 Hz can be evaluated

based on the rms continuous-current level.

The continuous-current capability is thermally constrained; therefore, the capability of the device varies across

the operating ambient temperature range.Figure 10 shows the maximum current-handling capability of the device

on the TMCS100EVM. Current capability falls off at higher ambient temperatures because of the reduced thermal

transfer from junction-to-ambient and a leadframe positive temperature coefficient that causes increased power

dissipation. By improving the thermal design of an application the SOA can be extended to higher currents at

elevated temperatures. Using larger and heavier copper power planes, providing air flow over the board, or

adding heat sinking structures to the area of the device can all improve thermal performance.

Figure 10. Maximum Continuous RMS Current vs Ambient Temperature