L9826_02 Ver la hoja de datos (PDF) - STMicroelectronics
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L9826_02 Datasheet PDF : 12 Pages
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L9826
Power outputs characteristics
for flyback current, outputs short circuit protection and diagnostics
For output currents flowing into the circuit the output voltages are limited. The typical value of this voltage is 50V.
This function allows that the flyback current of a inductive load recirculates into the circuit; the flyback energy is
absorbed in the chip.
Output short circuit protection for outputs 3 to 8 (dedicated for loads without inrush current): when the output
current exceeds the short circuit threshold, the corresponding output overload latch is set and the output is
switched off immediately.
Output short circuit protection for outputs 1 and 2 (dedicated for loads with inrush current, as lamps): when the
load current would exceed the short circuit limit value, the corresponding output goes in a current regulation
mode. The output current is determined by the output characteristics and the output voltage depends on the
load resistance. In this mode high power is dissipated in the output transistor and its temperature increases rap-
idly. When the power transistor temperature exceeds the thermal shutdown threshold, the overload latch is set
and the corresponding output switched off.
For the load diagnostic in output off condition each output features a diagnostic current sink, typ 60µA.
Diagnostics
The output voltage at all outputs is compared with the diagnostic threshold, typ 0,38 · VCC.
Outputs 1 and 2 features dedicated fault latches. The output status signal is filtered and latched. The fault latch-
es are cleared during NCS low. The latch stores the status bit, so the first reading after the error occurred might
be wrong. The second reading is right.
Diagnostic Table for outputs 1 and 2 in parallel controlled mode:
Output 1, 2
Output-voltage
Status-bit
Output-mode
off
> DG-threshold
high
correct operation
off
< DG-threshold
low
fault condition 2)
on
< DG-threshold
high
correct operation
on
> DG-threshold
low
fault condition 1)
Fault condition 1) "output short circuit to Vbat" : the output was switched on and the voltage at the output ex-
ceeds the diagnostics threshold. The output operates in current regulation mode or has been switched off due
to thermal shutdown. The status bit is low.
Fault condition 2) "open load" or "output short circuit to GND" : the output is switched off and the voltage at the
output drops below the diagnostics threshold, because the load current is lower than the output diagnostic cur-
rent source, the load is interrupted. The diagnostic bit is low.
For outputs 3 to 8 the output status signals, are fed directly to the SPI register.
Diagnostic Table for outputs 1 to 8 in SPI controlled mode:
Output 1 ... 8
Output-voltage
off
> DG-threshold
off
< DG-threshold
on
< DG-threshold
on
> DG-threshold
Status-bit
high
low
low
high
Output-mode
correct operation
fault condition 2)
correct operation
fault condition 1)
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