L9352

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1.0

Functional Description

1.1

Overview

The L9352 is designed to drive inductive loads (relays, electromagnetic valves) in low side configuration. Inte-

grated active Zener-clamp (for channel1 and 2) or free wheeling diodes (for channel 3 and 4) allow the recircu-

lation of the inductive loads. All four channels are monitored with a status output. All wiring to the loads and

supply pins of the device are controlled. The device is self-protected against short circuit at the outputs and over-

temperature. For each channel one independent push-pull status output is used for a parallel diagnostic func-

tion.

Channel 3 and 4 work as current regulator. A PWM signal on the input defines the target output current. The

output current is controlled through the output PWM of the power stage. The regulator limits of 10% or 90% are

detected and monitored with the status signal. The current is measured during recirculation phase of the load.

A test mode compares the differences between the two regulators. This “drift” test compares the output PWM

of the regulators. By this feature a drift of the load during lifetime can be detected.

1.2

Input Circuits

The INput, CLK, TEST and ENable inputs, are active high, consist of Schmidt triggers with hysteresis. All inputs

are connected to pull-down current sources.

1.3

Output Stages (not regulated) Channel 1 and 2

The two power outputs (5A) consist of DMOS-power transistors with open drain output. The output stages are

protected against short circuit. Via integrated Zener-clamp-diodes the overvoltage of the inductive loads due to

recirculation are clamped to typ. 52V for fast shut off of the valves. Parallel to the DMOS transistors there are

internal pull-down current sources. They are provided to assure an open load condition in the OFF-state. With

EN=low this current source is switched off, but the open load comparator is still active.

1.4 Current-Regulator-Stages Channel 3 and 4

The current-regulator channels are designed to drive inductive loads. The target value of the current is given by

the duty cycle (DC) of the 2kHz PWM input signal. The following figure shows the relation between the input

PWM and the output current and the specified accuracy.

Figure 3. Input PWM to output current range

10

90

250

2250

INPUT PWM[%]

400

800

±10%

+- 6%

+-10%