Analog Integrated Circuit Device Data



Freescale Semiconductor

41

33813

The inrush delay bit, in the SPI configuration register for each output, when set to a one(1), will prevent the over-current fault bit

5.3.7.5

Temperature Limit (OT) Protection

The second protection scheme works by sensing the local temperature of the individual output device. During an over-current

event, the device enters current limit and will remain in current limit until the output driver maximum temperature limit is exceeded

(OT). At this point, the device will shutdown automatically, regardless of the input state. The output will try to turn on again only

always enabled and is always a retry operation.

Outputs may be used in parallel to drive higher current loads provided the turn-off energy of the load does not exceed the energy

rating of a single output driver.

5.3.7.6

Output Driver Diagnostics

Over-current (OC), temperature limit (OT) exceeded, short to ground (SG), and open load (OL) conditions are reported through

the status register for each driver (no SG for the tachometer). Only open load and over-current are reported for pre-drivers. There

is also a bit in the SPI status register to indicate when any of the LSDs or pre-drivers are reporting a fault and when a particular

output has any of the four possible fault conditions present. This makes it easy for the MCU to poll for fault conditions by looking

for a single bit in one register to detect the presence of any fault in the circuit.

5.3.7.7

Open Load Pull-down Current Enable/Disable Bit

An open load condition is detected by the voltage level on the drain of the MOSFET in the off state. Internal to the device is a

pull-down current sink. In the event of an open load the drain voltage is pulled low by the current sink. When the voltage crosses

the open load threshold value, an open load condition is reported. This current sink may be disabled by clearing the appropriate

bit in the in the LSD configuration register. When the current sink is disabled, the off-state open load fault status bit will be forced

to a logic 0.

5.3.7.8

Open Load and Short to Battery Strategy

The injectors, lamps, relays, and tachometer low side outputs are capable of detecting an open load in the off state and short to

battery condition in the on state. All faults are reported through the SPI status register communication. For open load detection,

a current source is placed between the MOSFET drain pin and ground of the IC. An open load fault is reported when the drain

voltage is less than the listed threshold. Open load fault detect threshold is set internally to the listed threshold and may not be

programmed. A shorted load fault is reported when the drain pin voltage is greater than the programmed short threshold voltage

when the device is in the on state.

The open load and short to battery fault threshold voltage is fixed and cannot be modified via the SPI.

5.3.7.9

Short to Ground Strategy

The Injectors, Lamps, and Relays (but not the Tachometer) low side driver outputs are capable of detecting a short to ground

when the output is turned on by measuring the current flow in the output device and comparing it to a known current value. If a

short to ground is detected it is annunciated via a bit in the appropriate SPI status register.

Table 20. Inrush Delay Bit

Inrush Delay Bit

Timer Value

0

1