L9026 datasheet(21/60 Pages) STMICROELECTRONICS

21 / 60 page

Figure 9. Switching resistive loads

7.1.2

Inductive output clamp

When switching off inductive loads, the voltage across the power switch rises to VDS(CL) potential, because the

inductance intends to continue driving the current. In case of HS configuration, the potential at Output pin is not

allowed to go below VOUT_S(CL). The voltage clamping is necessary to prevent device destruction.

To clarify this idea Figure 10 shows a concept drawing of the implementation.

Nevertheless, the maximum allowed load inductance is limited by the max energy. The clamping structure

protects the device in all operative modes (Sleep, Idle, Active, Limp Home).

Figure 10. Output clamp concept

7.1.3

Maximum load inductance

During demagnetization of inductive loads, energy has to be dissipated device. Eq. (1)shows how to calculate the

energy for low-side switches, while Eq. (2) can be used for high-side switches (auto-configurable switches can

use all equations, depending on the load position):

E=VDSCL ⋅ VS−VDSCL

RL ⋅In⋅ 1− RL⋅IL

VS−VDSCL +IL ⋅ LRL

(1)

E= VS−VDSCL ⋅ VOUTSCLRL ⋅In⋅ 1− RL⋅IL

VOUTSCL +IL ⋅ LRL

(2)

The maximum energy, which is converted into heat, is limited by the thermal design of the component. The

EAR value provided in Table 14 assumes that all channels can dissipate the same energy when the inductances

connected to the outputs are demagnetized at the same time.

L9026

Operating modes

DS13397 - Rev 5

page 21/60

L9026 数据表(PDF) 21 Page - STMicroelectronics