L9524C

Functional description

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4.9

Relay output

In relay mode (modes 1 and 2) the IO pin is used as output pin to control an external relay

driver (e.g. a low-side switch which drives the relay). If the output stage of the IO pin is

switched on it behaves like a voltage source (VIO) with output resistance RIO. If it is switched

off a pull-down current source is activated (IIO). The relay output suppresses pulses shorter

than tIO sup such that the relay can be permanently switched by applying appropriate PWM

signals to the CI pin (see section “Control input”).

In transistor mode (modes 3 to 6) the IO pin is used as input pin. Left open it is pulled down

to ground and the power regulation feature (see section “Power regulation”) is activated

(VIO <VIO pr). To deactivate the power regulation feature the IO pin must be connected to

the CUR pin (VIO = VCUR > VIO pr).

4.10

Gate charge/discharge current variation

The CUR pin provides a constant current-limited output voltage VCUR. The gate charge (or

discharge) current is a multiple of the current flowing out of the CUR pin and can therefore

be varied by applying a resistor to the CUR pin.

In order to select the mode of operation the IO pin and/or the MS pin may be connected to

the CUR pin (see section “Modes”). The IO pin contains a pull-down current source and the

MS pin contains a pull-up current source. These currents are compensated if the

corresponding pin is connected to the CUR pin in order not to affect the gate

charge/discharge current.

4.11

Overcurrent threshold variation

The overcurrent threshold

V

OC can be varied by connecting the OCT pin to an external

resistive voltage divider between CUR pin and ground. If the OCT pin is left open it is pulled

up to an internal supply voltage by a current source and a default value is used for the

overcurrent threshold. This default value corresponds to the condition: VOCT = VCUR/6. In

order not to de tune the voltage divider the pull-up current IOCT source is deactivated when

any glow plug is switched on.