L9524C

Functional description

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Though in mode 2 (relay mode, serial diagnostic interface protocol) the relay should be

switched permanently the L9524C also expects a PWM signal at the CI pin since the serial

diagnostic interface protocol is synchronized by falling edges of the CI signal (see section

“Diagnostic output”). The relay then is switched on permanently if the off time (time between

rising and falling edge) of the PWM signal is less than tIO sup since the relay output

suppresses pulses shorter than tIO sup (see section “Relay output”). For the same reason the

relay is switched off permanently if the on time (time between falling and rising edge) of the

PWM signal is less than tIO sup. In all other cases the relay is switched according to the

PWM signal at the CI pin.

Figure 6.

Control input signal in mode 2 for permanent switch on

In mode 1 (relay mode, go/no-go diagnostic interface protocol) no edges are necessary for

the go/no-go protocol. Therefore the relay is switched on if VCI = VCI on and it is switched off

if VCI = VCI off.

4.4

Diagnostic output

The diagnostic output stage of the L9524C (DO pin) consists of a current-limited low-side

switch and a pull-up resistor RDO to the VS pin. The voltage level of a logical low signal VDOL

is given by the drop across the low-side switch and the voltage level of a logical high signal

is equal to VVS.

The L9524C is able to detect the following failures (see sections “Supply”, “Current

monitoring”, and “Switch monitoring”):

●

open-load (6 glow plugs),

●

overcurrent (6 glow plugs, stored until power-down),

●

any switch is defect (4 switches),

●

supply voltage (VVS) is too low (“under voltage”),

●

supply voltage (VVS) is too high (“over voltage”),

●

junction temperature (TJ) is too high,

●

charge pump voltage (VCP) is too low (“charge pump under voltage”), and

●

battery voltage (VBAT) is too low (“battery under voltage”).

V

CI

t

V

CI off

V

CI on

0.6 . V

VS

0.4 . V

VS

t

relay

ON

OFF

T

CI

t

IO sup

t

IO sup

t

CI fil +tdel