As discussed previously, when switching off, supply energy and load energy are dissipated on the high-side

power switch, which leads to the large thermal variation. For each high-side power switch, the upper limit of

the maximum safe power dissipation depends on the device intrinsic capacity, ambient temperature, and board

dissipation condition.

8.3.3.5 Inductive Load Demagnetization

When switching off an inductive load, the inductor can impose a negative voltage on the output of the switch.

The TPS274C65 includes voltage clamps between VS and VOUT to limit the voltage across the FETs and

demagnetize load inductance if there is any. The negative voltage applied at the OUT pin drives the discharge

of inductor current. Figure 8-12 shows the device discharging a load of 100 mH paralleled with 48 Ω, resulting

500mA at the turn-off.

Figure 8-12. TPS274C65 Inductive Discharge (100 mH + 48 Ω)

The maximum acceptable load inductance is a function of the energy dissipated in the device and therefore the

load current and the inductive load. The maximum energy and the load inductance the device can withstand for

one pulse inductive dissipation at 125°C is shown in Figure 8-13. The device can withstand 40% of this energy

for one million inductive repetitive pulses with a 2-Hz repetitive pulse. If the application parameters exceed this

device limit, use a protection device like a freewheeling diode to dissipate the energy stored in the inductor.

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Current (A)

120

160

200

240

280

320

360

400

440

480

520

VS = 24 V

Figure 8-13. Maximum Energy Dissipation (EAS) Allowed TJ, START = 125°C - Single Pulse, One Channel

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TPS274C65CP

SLVSH35A – OCTOBER 2023 – REVISED FEBRUARY 2024

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