Datasheet

Analog Integrated Circuit Device Data
36 Freescale Semiconductor
10XSC425
6.3 Protection and Diagnostic Features
6.3.1 Protections
6.3.1.1 Overtemperature Fault
The 10XSC425 incorporates overtemperature detection and shutdown circuitry for each output structure.
Two cases need to be considered when the output temperature is higher than T
SD
:
• If the output command is ON: the corresponding output is latched OFF. FSB will be also latched to logic [0]. To delatch the
fault and be able to turn the outputs ON again, the failure condition must disappear and the autoretry circuitry must be
active, or the corresponding output must be commanded OFF and then ON (toggling fault_control signal of corresponding
output), or V
SUPPLY(POR)
condition, if V
DD
= 0.
• If the output command is OFF: FSB will go to logic [0] till the corresponding output temperature will be below T
SD
.
For both cases, the fault register OT[0:3] bit into the status register will be set to [1]. The fault bits will be cleared in the status
register after a SPI read command.
6.3.1.2 Overcurrent Fault
The 10XSC425 incorporates output shutdown, to protect each output structure against a resistive short-circuit condition. This
protection is composed by eight predefined current levels (time dependent) to fit Xenon-HID manners by default or, 55
W or
28 W bulb profiles, selectable separately by Xenon bit and 28 W bits (as illustrated Figure 14).
At the first turn-on, the lamp filament is cold and the current will be huge. The fault_control signal transition from logic [0] to [1],
or an autoretry define this event. In this case, the overcurrent protection will be fitted to inrush current, as shown in Figure 5. This
overcurrent protection is programmable: OC[1:0] bits select the overcurrent slope speed and the OCHI1 current step can be
removed in case the OCHI bit is set to [1].
In steady state, the wire harness will be protected by a OCLO2 current level by default. Three other DC overcurrent levels are
available: OCLO1, or OCLO3, or OCLO4, based on the state of the OCLO[1,0] bits.
If the load current level ever reaches the overcurrent detection level, the corresponding output will latch the output OFF and FSB
will be also latched to logic [0]. To delatch the fault and be able to turn the corresponding output ON again, the failure condition
must disappear and the autoretry circuitry must be active, or the corresponding output must be commanded OFF and then ON
(toggling fault_control signal of corresponding output), or V
SUPPLY(POR)
condition, if V
DD
= 0.
The SPI fault report (OC[0:3] bits) is removed after a read operation.
In Normal mode using the internal PWM module, the 10XSC425 also incorporates a cooling bulb filament management, if
OC_mode and
Xenon are set to logic [1]. In this case, the first step of multi-step overcurrent protection will depend on the previous
OFF duration, as illustrated in
Figure 6. The following figure illustrates the current level that will be used in the function to the
duration of the previous OFF state (t
OFF
). The slope of the cooling bulb emulator is configurable with OCOFFCB[1:0] bits.
hson signal
Over-current thresholds
PWM
fault_control
hson