Circuit description

L9338

10/14

Doc ID 1766 Rev 5

4

Circuit description

The L9338 is a quad low side driver for lines, lamps or inductive loads in automotive and

industrial applications.

All inputs are TTL or CMOS compatible. This allows the device to be driven directly by a

microcontroller. For the noise immunity, all inputs have a Schmitt-trigger with a hysteresis of

typ. 100 mV.

Each input stage has an input voltage protection from -24 V to 45 V. The device can be

activated with a ’high’ signal on Enable (EN) input. Enable ’low’ switches the device into the

sleep mode. In this mode the quiescent current is less than 10 mA. A high signal on

programming (PRG) input changes the signal transfer polarity from non inverting into the

internally fixed at low status by open input condition.

Independent of the programming input, the output (OUT) switches off, if the signal input (IN)

pin is not connected.

Each output driver has a current limitation of min. 0.4 A and a separate thermal shut-down.

The thermal shut-down deactivates that output which exceeds temperature switch off level.

About 20K below this temperature threshold the output will be activated again. This means,

that each output is able to sink continuously 285 mA without activating thermal shut-down at

85 °C ambient temperature. The slew rate of the output is limited to max. 14 V/ms to reduce

the electromagnetic interference, but not for the enable transfer characteristic (see

Figure 3). An integrated active flyback voltage limitation clamps the output voltage during

the flyback phase of inductive loads to typ. 50 V. The power DMOS switches ON, if the

device is enabled and the output swings below ground. This protection avoids the activation

of parasitic inside the power DMOS.

The diagnostic (DIAG) is an open drain output. The logic status depends on the

programming pin. If the PRG pin is ’low’ the DIAG output becomes low, if the device works

correctly.

At thermal shut-down of one channel, disconnected ground or supply voltage the diagnostic

output becomes high. If the PRG pin is ’high’ this output is switched off at normal function

and switched on at over temperature.

Table 7.

Diagnostic

Pins

EN

PRG

IN

OUT

DIAG

Normal function

H

L

L

L (on)

L (on)

H

L

H

H (off)

L (on)

H

H

L

H (off)

H(off)

H

H

H

L (on)

H(off)

L

X

X

H (off)

H(off)

Over temperature, disconnected

ground or supply voltage

H

L

X

1.

Selective for each channel at over temperature.

X = not relevant.

H (off)

Over temperature

H

H

X

H (off) (1)

L (on)