
L9352B
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1
Functional Description
1.1
The L9352B is designed to drive inductive loads (relays, electromagnetic valves) in low side configuration. In-
tegrated active Zener-clamp (for channel1 and 2) or free wheeling diodes (for channel 3 and 4) allow the recir-
culation 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 limit of 90% is 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.
Overview
1.2
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.
Input Circuits
1.3
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.
Output Stages (not regulated) Channel 1 and 2
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
250
10 16
32
90
400
800
2250
IO
(mA)
INPUT PWM(%)
mA
±
10%
±6%
-8% to +6%
D03AT513A