L9524C datasheet(13/27 Pages) STMICROELECTRONICS

13 / 27 page

L9524C

Functional description

13/27

Figure 3.

Shunt sense versus transistor sense

4.2

Supply

The main supply pin of the L9524C is the VS pin. The voltage applied to it (VVS) is

monitored

●

to switch off all glow plugs if it is less than VVS uv for at least tVS fil (“under voltage

failure”),

●

to switch off all glow plugs if it is greater than VVS ov for at least tVS fil (“over voltage

failure”),

●

to switch on all glow plugs if it is greater than VVS ld for at least tVS ld (“active clamping

during load dump”),

●

to ignore open-load failures if it is less than VVS ol.

Note:

The glow plugs are switched on again if the corresponding switch-on condition disappears,

except if the glow plugs are switched on because of load dump. Then they remain switched

on until VVS is less than VVS ov for at least tVS fil.

In modes 2 to 6, the L9524C is additionally supplied by the BAT pin. This auxiliary supply

ensures that the external power MOSFET’s are switched off if no main supply voltage is

available at the VS pin.

The BAT pin is additionally used to sense the battery voltage VBAT for power regulation in

modes 4 and 6 (see section “Power regulation”) and for detecting “battery under voltage

failure” (fuse between battery and module is defect) if VBAT is less than VBAT uv for at least

tBAT fil in modes 2 to 6.

An additional supply voltage higher than the main supply voltage is generated by an internal

charge pump which charges an external storage capacitor connected to the CP pin. This

capacitor mainly supplies the gates of the external n-channel power MOSFET’s. The charge

pump voltage VCP is monitored and the glow plugs are switched off if it is less than VCP uv

for at least tCP fil (“charge pump under voltage”). Afterwards, the glow plugs remain switched

off even if the charge pump voltage becomes greater than VCP uv until they are explicitly

switched on again by the CI (control input) pin.

glow plug

shunt

BAT

SPx

SNx

glow plug

BAT

SPx

SNx

shunt sense

transistor sense

015

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