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 “shunt sense”) or using the R
DS(on)
of the power MOSFET’s themselves
(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
R
DS(on)
of the power MOSFET’s is assumed to vary with respect to the temperature and
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
