AN4402 datasheet(8/39 Pages) STMICROELECTRONICS

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Active clamp of the L99MC6 and L9733

AN4402

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DocID025557 Rev 1

2.2.1

Case 1: VBAT ≤ VCL_LS - VCL_HS

During turn-off, the evolution of the voltage across the inductor causes VS to go negative

(Figure 2) and the gate-source clamp (Figure 3) is activated when VS = -VCL_HS.

Note:

In this document VCL_HS is considered positive.

VS is maintained at -VCL_HS. Therefore VDS = VBAT + VCL_HS < VCL_LS and the gate-drain

clamp is not activated.

Figure 4. L99MC6 high-side during the turn-off, VBAT < VCL_LS - VCL_HS

Case 1 corresponds to a demagnetization of the inductive load at typically VBAT ≤ 16 V for

the L99MC6 and at VBAT ≤ 36 V for the L9733. It is applicable to the nominal battery voltage

for automotive applications (13.5 V).

Note:

The gate-source clamp only maintains VS to -VCL_HS. iL is still supplied by the battery and

not by the gate-source clamp.

Table 1. Specification of clamping voltages - L99MC6 and L9733

L99MC6

L9733

Typ. VCL_LS

35 V

Datasheet parameter:

VDRN_CL1-6

55 V

Datasheet parameter:

DRN1-8CL

Typ VCL_HS

19 V

Datasheet parameter:

│V

SRC_CL1-3│

19 V

Datasheet parameter:

│SRC_1-8CL│

VBAT limit for case1 /

case2

16 V

36 V

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