Functional description

L9524C

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In order to report the occurrence of any of the above-listed failures to the diesel engine

management system the L9524C provides two protocols: go/no-go protocol for mode 1 and

serial protocol for modes 2 to 6.

The go/no-go protocol is only able to report if any of the above-listed failures occurred. This

is done according to the following table:

Note:

overcurrent failures are stored until power-down.

The serial protocol is able to report different kinds of failures and to assign them to the

corresponding glow plugs. Therefore, occurring failures are written into an internal 8-bit

failure register:

Bits 1 to 6 are assigned to the glow plugs. Depending on bit 7 they show open-load (bit 7 is

low) or overcurrent failures (bit 7 is high). Bit 8 shows if there is any of the listed failures

(“module failure”). In case of a battery under voltage failure bits 7 and 8 are high and all

other bits are low as long as there is no overcurrent failure stored.

For transmitting the contents of the failure register the PWM signal applied to the CI pin is

used as clock input: at any falling edge of the CI signal (see section “Control input”) the DO

pin shows the value of the next bit of the bit stream after tDO del.

Table 7.

Go / no-go protocol description

VCI

VDO at “no failure”

VDO at “any failure”

VCI off

VDOL

VVS

VCI on

VVS

VDOL

Table 8.

Failure register description

Bit

Meaning of high state

1

Open-load or overcurrent (1) failure at glow plug 1

1.

overcurrent failures are stored until power-down

2

Open-load or overcurrent (1) failure at glow plug 2

3

Open-load or overcurrent (1) failure at glow plug 3

4

Open-load or overcurrent (1) failure at glow plug 4

5

Open-load or overcurrent (1) failure at glow plug 5

6

Open-load or overcurrent (1) failure at glow plug 6

7

Overcurrent failure at any glow plug (1) or

battery voltage (VBAT) is too low

(2) (“battery undervoltage”)

2.

if battery voltage is too low (“battery under voltage”) bits 7 and 8 are high

8

One or more of the following failures (“module failure”):

any switch is defect

supply voltage (VVS) is too low (“undervoltage”)

supply voltage (VVS) is too high (“overvoltage”)

junction temperature (TJ) is too high

charge pump voltage (VCP) is too low (“charge pump undervoltage”)

battery voltage (VBAT) is too low

(2) (“battery under voltage”)