L9524C datasheet(14/27 Pages) STMICROELECTRONICS

14 / 27 page

Functional description

L9524C

14/27

4.3

Control input

The control input (CI) pin is resistively pulled up RCI to the supply voltage VVS such that

VCI=VCI off and the glow plugs are switched off by default. The L9524C is controlled by

transitions of VCI from VCI off to VCI on (falling edge) and vice versa (rising edge). Voltage

level changes of VCI which last shorter than tCI fil are ignored.

In transistor mode (modes 3 to 6) the L9524C expects a PWM signal at the CI pin. Each

falling edge starts measuring its on time tCI on (time until next rising edge, i.e. length of this

low pulse) and its period TCI (time until next falling edge). The end of a pulse group is

detected if no falling edge occurs for a time greater than tCI to and the glow plugs are

switched off. Therefore, it is not possible to switch on the glow plugs permanently with one

exception: if the low voltage level of the first falling edge is greater than VCI to the glow plugs

remain switched on as long as this low pulse lasts.

Figure 4.

Control input signal in transistor mode (modes 3 to 6)

Figure 5.

Permanent switch on of glow plugs at first falling edge in transistor mode

(modes 3 to 6)

CI off

CI on

0.6 . V

0.4 . V

glow plug

OFF

CI to

CI on

CI to

CI fil

CI fil +t del

ignored

(shorter than t

CI fil )

VCI

VCI off

VCI on

0.6

. V

0.4

. V

glow plug

OFF

tCI to

VCI to

tCI to

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