L9924L datasheet(33/84 Pages) STMICROELECTRONICS

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L9924L

Electrical specifications

Figure 13. Lamp driver overcurrent protection function

The minimum Tretry can be calculated in the following way:

The high side driver is switched off if the current overcomes the ILOVCHS for tLfilterHS time

and bit 3 of SPI read register 0x12 is set [12.4.6].

Low-side and the high-side have independent commands through bits 4 and 5 of SPI write

voltage exceeding V(A+/B+) by VLrevHS. In this case the high-side is internally forced into

off-state (high-side recirculation is not possible).

The L pin can be used for the RVC protocol (RVC drive mode) if the suitable configuration

has been selected setting bit 6 of SPI write register 0x09 [12.4.17] to change the gate

control in alarm condition for the low side MOS connected to the pin (drain voltage

regulation at VLRVC, fault.

To reduce, in lamp drive mode, the power dissipation in the lamp driver while it is on, the

following strategy is implemented: after key-on, as soon as the L pin voltage overcomes

VLHTh, after tfilt time it is brought to VLsat voltage (between its drain and source), then the

key status is verified every twait time intervals within a tchk,to time window.

During this window, if the key is switched on the L voltage reaches the VLkey_chk value and

immediately returns to the VLsat value before the window expiration whereas, if the key is no

longer active, the L voltage cannot increase and remains to VLsat voltage level.

Note:

If a bulb is connected on the L pin, the in-rush phase can generate an over-current fault

leading to the impossibility of bulb turn-on. In this case the software must use a "lamp soft

switch-on procedure", see below example Figure 14.

Tretry

ILlimLS TLoc VA+/B+



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Pretry

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