l9733 STMicroelectronics, l9733 Datasheet - Page 26

• Manufacturer Part Number: l9733
• Description: Octal Self Configuring Low/high Side Driver
• Manufacturer: STMicroelectronics

Fault operation
7.2
7.2.1
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High side configured output fault operation
The diagnostic circuitry verifies for the high side configured output the following condition:
Normal operation, open load, short circuit to Vbat and overcurrent (only if the switching OFF
protection, selectable for each channel via SPI bus, is active).
The diagnostic circuitry operates in two different modes, selected for each channel by SPI:
no latch mode and latch mode. The fault priority is overcurrent and then open load or short
circuit to Vb, this means that if an overcurrent occurs the fault register is always overwritten
and following open load or short to Vbat faults that happen before that the register is cleared
will be ignored.
No latch mode
This diagnostic operating mode doesn't latch open load and short to Vbat faults.
1.
2.
3.
phase overcurrent protection is a linear current limitation and no diagnosis is available.
There are three possibilities to restart one output after the fault has occurred:
–
–
–
Open load
The diagnostic of open load is detected only in OFF condition sensing the Src1-8
output voltage. This fault is detected on the falling edge of the CS input if the power
drain voltage is inside the voltage range limited by the two thresholds Vth_Vbat and
Vth_GND. An internal current limited voltage regulator fixes the drain voltage inside the
described range when no load is connected.
Short Circuit to Vb
The diagnostic of short circuit to Vbat is detected only in OFF condition sensing the
Src1-8 output voltage. This fault is detected on the falling edge of the CS input if the
power drain voltage is higher than the Vth_Vbat threshold.
Overcurrent
The diagnostic of overcurrent is detected only in ON condition, if the switching OFF
protection of the channel is enabled (default), sensing the current level of the output
power transistor. If the output current has been above the short threshold Iovc for the
filtering time Tdel the output power is switched off and at the same time an overcurrent
Automatically after a time Tres
On the rising edge of CS if two valid DI byte has been received and first the Output
Status in the command register is written with logic '0' and then with a logic “1” in
the following SPI cycle
On the rising edge (low to high transition) at the corresponding parallel input pin
(only for Outputs 6-8).
If the power MOS transient, after a switching-off command, is longer than Tdel
filtering time, a bad diagnostic behavior happens and software filtering may be
needed.
L9733