LDLL16ENTR datasheet(25/102 Pages) STMICROELECTRONICS

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4.3.8

Channel output – short circuit to VPREG

The LDLL16EN features the output channel voltage shortage detection versus the external pre-regulator, both in

bus mode and fail-safe/stand-alone mode, by comparing the voltage difference between VPREG and VOUTx (VLED)

versus a fixed threshold (VOUT_SHT_PREG_TH).

The short to VPREG detection is masked when the LED supply voltage (VPREG) is below a power good threshold

(VPG_TH_VPREG), which is configurable in the range of (VPG_TH_VPREG_min ÷ VPG_TH_VPREG_max) with a step

equal to VPG_TH_VPREG_step.

There is one status bit (PG_NOT_VPREG, see the Section 6: FTP and RAM memory mapping) to indicate the

selected voltage threshold is reached. If this bit is equal to "1", the desired voltage threshold is not reached and

the diagnostic disabled; otherwise, the threshold is reached and the diagnostic enabled.

After power good threshold is reached, the fault detection starts and the channel is recognized in fault as soon as

VLED is less than the specified threshold (VOUT_SHT_PREG_TH).

If a shortage between a channel output and the pre-regulated voltage is detected, the related channel bit

(OUT_SHT_VPREG_CHx, see the Section 6: FTP and RAM memory mapping) is set.

When this flag is set, the faulty channel is disabled regardless of the setting of its own short off

(SHT_OFF_GROUP_X) bit. The OUT_SHT_VPREG_CHx flag is a Read & Clear bit: channel "x" is latched off in

case of fault, it will restart after bit clearing. If fault is still there, the channel will be latched off again.

In case of fail-safe/stand-alone mode, after elapsing the tAUTORESTART, the faulty channel is automatically re-

activated and the OUT_SHT_VPREG_CHx bit is cleared.

Channel output short to pre-regulator voltage event is also reported in the global status byte register, in particular

functional error 2 (FE2) bit is set.

For all (and only) those channels mapped on DIN (DIN_MAP_CHx = 1), the LDLL16EN features the indication of

short circuit to VP_REG on FAULT pin.

If the bit SHT_EN (see the Section 6: FTP and RAM memory mapping) is equal to "0", the short circuit fault

detection is NOT propagated on FAULT bus; whilst if SHT_EN = 1, the short circuit of the faulty channel is

indicated on associated FAULT bus (pulled low).

Then, for both mapped and non-mapped channels, according to the status of the fault reaction mode

configuration bit (see Table 8), an automatic deactivation of the complete light function respectively of the faulty

channel only is performed.

The flow chart reported in the Figure 15 shows how the device manages the faulty channel and the channels

corresponding to DIN_MAP_CHx as well as the fault pin handling.

LDLL16EN

Functional description

DS14111 - Rev 5

page 25/102

LDLL16ENTR Datasheet(PDF) 25 Page - STMicroelectronics