LDLL16ENTR datasheet(23/102 Pages) STMICROELECTRONICS

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This configurability allows the short detection of one or more LEDs shortage within the string connected to a given

channel mapped according to DIN_MAP_CHx <0>.

The LED short circuit 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 short circuit detection starts and the channel is recognized in fault as

soon as its output voltage, read by ADC - is higher than the specified threshold (VSHT_TH_GROUP_X).

Table 9. LED short circuit threshold - group

DIN_MAP_CHx <0>

Short circuit threshold group

Short circuit threshold for Group 0 (VSHT_TH_GROUP_0)

Short circuit threshold for Group 1 (VSHT_TH_GROUP_1)

The short circuit detection can be enabled /disabled through the SHT_DET_EN bit (see the Section 6: FTP and

RAM memory mapping): if this bit is equal to "0", the short circuit detection is disabled (that is, if the channel is

directly supplied from VS instead of a pre-regulated voltage, it is recommended to disable short circuit detection,

to avoid erroneous fault detection during voltage drops on VS line); otherwise, the short circuit detection is

enabled. In this latter case, two different scenarios are possible: enable or disable the channel output deactivation

in case of short circuit, by one dedicated bit per each group (SHT_OFF_GROUP_X, see the Section 6: FTP and

RAM memory mapping). If SHT_OFF_GROUP_X bit is set to 0, the faulty channel output is kept active in case of

short circuit, otherwise the faulty channel is latched off. The channel is recognized in short circuit as soon as its

output voltage, read by ADC, is less than the specified short circuit threshold (VSHT_TH_GROUP_X, see Table 9).

In bus mode, the faulty channel output is latched off and the dedicated fault bit (SHT_CHx, see the

Section 6: FTP and RAM memory mapping) is set. The channel output can be restarted and the fault bit will be

cleared by sending a read and clear command to address 28h. Selective bitwise read and clear is possible.

In case of fault in fail-safe/stand-alone mode:

•

for the channels configured with FS_OUTx_EN = 0, the output is latched off and it is cleared upon falling

edge of DIN with tDIN_FALL settling time. This means that fault is not cleared during PWM dimming with

PWM off-time shorter than tDIN_FALL time.

•

for the channels configured with FS_OUTx_EN = 1, after elapsing the tAUTORESTART, the faulty channel is

automatically re-activated and the SHT_CHx bit is cleared.

If outputs are permanently enabled by FS_OUTx_EN = 1, in case of LED short circuit, they will be latched and the

latch can be cleared only through a power on reset condition.

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

circuit 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).

The LED short event is also reported in the global status byte register, in particular functional error 2 (FE2) bit is

set.

Then, for both mapped and non-mapped channels, according to the fault reaction mode configuration bit (see the

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 14 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 23/102

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