L99LDLH32TR datasheet(36/142 Pages) STMICROELECTRONICS

36 / 142 page

Functional description

L99LDLH32

36/142

DS12879 Rev 6

5.3.8

Channel output - short circuit to GND

The L99LDLH32 features the output channel voltage shortage to GND - both in Bus mode

as well as Fail Safe / Stand Alone mode - based on voltage monitoring across the channel

output voltage: the detection is done by comparing the absolute output voltage versus a

fixed threshold (VOUT_SHT_GND_TH).

The short circuit to GND detection is masked when the O/LED supply voltage is below a

power good threshold (VPG_TH_VPRE_REG).

When the channel output voltage is lower than the VOUT_SHT_GND_TH threshold, a shortage

between a channel output and GND is detected and the related channel bit

(OUT_SHT_GND_CHx– see RAM memory map, Chapter 7) is set. In case the LED short

detection threshold (either VSHT_CH_TH or VSHT_CH_DIN_TH) is set lower than the channel

short to ground threshold (VOUT_SHT_GND_TH), this latter protection has the highest priority.

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

off (SHT_OFF_x) bit. This 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_GND_CHx bit is cleared.

Channel output short to GND voltage event is also reported in the Global Status Byte

For all (and only) those channels mapped on DIN (DIN_MAP_CHx = 01), the L99LDH32

features the indication of short circuit to GND on FAULT pin. If the SHT_EN bit (see

FTP/RAM memory map, Chapter 7) 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 Figure 11 shows how the device manages the faulty channel and

the channels corresponding to DIN_MAP as well as the fault pin handling.

L99LDLH32TR Datasheet(PDF) 36 Page - STMicroelectronics