LDLL16ENTR datasheet(22/102 Pages) STMICROELECTRONICS

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4.3.3

Thermal warning

The LDLL16EN integrates a temperature warning with one threshold.

If the junction temperature (TJ) of the device, read by 8-bit internal ADC, rises above the threshold (TTW), the

thermal warning status bit (TW, see the Section 6: FTP and RAM memory mapping) is set. Thermal warning is

also reported in the global status byte register, in particular global warning (GW) bit is set.

As soon as the TJ drops below the thermal warning reset threshold (TTW - TTW_HYST), the corresponding thermal

warning status bit is automatically cleared.

Even if a temperature warning is detected, device as well as output channels are kept functional.

To avoid further temperature increase, it is possible to start a thermal derating, if set, when thermal warning

threshold is reached.

4.3.4

Thermal shutdown

If the junction temperature of the LDLL16EN rises above the shutdown temperature threshold (TTSD), a thermal

shutdown event is detected: all the output channels are switched off and the thermal shutdown status bit (TSD,

see the Section 6: FTP and RAM memory mapping) is set. The fault pin (FAULT) is pulled low.

Thermal shutdown event is also reported in the global status byte register, in particular functional error 1 (FE1) bit

is set.

As soon as the TJ drops below the thermal shutdown reset threshold (TTSD - TTSD_HYTS), the output channels are

automatically re-activated. The corresponding thermal shutdown status bit (TTSD) is automatically cleared as soon

as TJ drops below the thermal shutdown reset threshold (TTSD - TTSD_HYST), contemporarily to channel re-

activation.

In case of thermal shutdown, device logic and state machine remain active.

4.3.5

LED current derating

In case of temperature increasing, the device performs an automatic LED current derating based on the

measurement of external NTC voltage as well as on the internal device temperature (TJ).

An integrated thermal sensor is used to sense the device junction temperature (TJ) as well as to detect thermal

warning (TW) and thermal shutdown (TSD) thresholds, granting device protection in case of temperature

increasing. The sensed junction temperature (TJ) is monitored by 8-bit ADC with the aim of starting an automatic,

downwards derating of the LED string current as soon as the TW threshold is reached. The derating ends when

the value (I_PROG-Imin)/2+Imin of LED current is reached, which corresponds to TJ = 165 °C.

The 8-bit ADC is also used to monitor the voltage on the NTC pin, where an external resistor can be connected. If

the monitored voltage, whose value depends on the temperature detected by the NTC resistor itself - reaches the

VNTC_TH threshold (programmable by 3 bits, see the Table 64), a downwards derating of the LED string current

automatically starts, till a fraction of the nominal LED current is reached , this LED current end value is calculated

as (I_PROG-Imin)/2+Imin. This corresponds to a NTC temperature 20 °C higher than VNTC_TH.

The monitoring of both TJ and NTC voltage is contemporarily active. The actual derating is determined by the

parameter which would require the most severe derating.

4.3.6

VS undervoltage lockout

If the VS supply falls below VS undervoltage threshold (VS_UV), the device is deactivated - regardless of the

operating mode, and the fault pin (FAULT) is pulled low. This feature is implemented, in order to avoid any

operation outside the allowed VS operating range.

If supply undervoltage event is detected, the related flag (VS_UV, see the Section 6: FTP and RAM memory

mapping) is set and reported also in the global status byte register, where device error (DE) bit is set.

As soon as the VS supply crosses the undervoltage reset threshold (VS_UV_RST) the device is automatically re-

activated.

4.3.7

Channel output – LED short circuit detection

The LDLL16EN features the LED (single or multiple) short circuit fault detection, both in bus mode and fail-safe/

stand-alone mode, based on voltage monitoring across the channel output voltage: the detection is done by

comparing the absolute output voltage (VOUTx) versus a configurable threshold.

The device features 2 configurable short circuit thresholds (VSHT_TH_GROUP_X, see the Table 9).

LDLL16EN

Functional description

DS14111 - Rev 5

page 22/102

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