Functional description

L9524C

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4

Functional description

4.1

Operating modes

The L9524C can operate in a total of 6 modes. The selection is done by short-circuiting the

appropriate pins and voltages as shown in the following table:

Modes 1 and 2 are for relay usage (referred to as “relay mode”) and modes 3 to 6 for

transistors usage (referred to as “transistor mode”).

In relay mode the protocol of the diagnostic interface (DO pin) can be selected from go/no-

go protocol and serial protocol (see section “Diagnostic output” for protocol description).

In transistor mode the protocol of the diagnostic interface is the serial protocol. It can be

distinguished between using shunts for monitoring the current through the glow plugs

(referred to as “transistor sense”). In shunt sense mode the resistance of the shunt is

assumed to be constant with respect to the temperature while in transistor sense mode the

therefore overcurrent monitoring is adjusted appropriately.

In transistor mode there are two possibilities to control the output timing. In modes 3 and 5

the timing of the PWM control input signal determines the timing of the PWM signals applied

to the external power MOSFET’s (“no power regulation”). In modes 4 and 6 the timing of the

PWM control input signal determines the power through the glow plugs (“power regulation”)

and the timing of the PWM signals applied to the external power MOSFET’s is adjusted

depending on the battery voltage (see section “Power regulation”).

Table 6.

Mode

Mode

Description

MS pin

BAT pin

IO pin

CI pin

1

relay mode, go/no-go diagnostic interface protocol

ground

ground

output

statical signal

2

relay mode, serial diagnostic interface protocol

ground

battery

output

PWM signal

3

transistor mode, shunt sense, no power regulation

CUR pin

battery

CUR

pin

PWM signal

4

transistor mode, shunt sense, power regulation

CUR pin

battery

ground

PWM signal

5

transistor mode, transistor sense, no power regulation

open

battery

CUR

pin

PWM signal

6

transistor mode, transistor sense, power regulation

open

battery

ground

PWM signal