CIRCUIT DESCRIPTION
The L9838 is a quad low side driver for lines,
lamps or inductive loads in automotive and indus-
trial applications.
All INputs are TTL or CMOS compatible. This al-
lows the device to be driven directly by a micro-
controller. For the noise immunity, all inputs have
a Schmitt-trigger with a hysteresis of typ. 100mV.
Each input stage has an input voltage protection
from -24V to 45V. The device can be activated
with a ’high’ signal on ENable input. ENable ’low’
switches the device into the sleep mode. In this
mode the quiescent current is less than 10
µ
A. A
high signal on PRoGramming input changes the
signal transfer polarity from noninverting into the
inverting mode. Normally this pin is connected to
V
S
or GND. These pins (PRG and EN) are inter-
nally fixed at low status by open input condition.
Independent of the PRoGramming input, the
OUTput switches off, if the signal INput pin is not
connected.
Each output driver has a current limitation of min
0.4A and a seperate thermal shut-down. The ther-
mal shut-down deactivates that output which ex-
ceeds 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 285mA without acti-
vating thermal shut-down at 85°C ambient tem-
perature (SO20). The slew rate of the output is
limited to max. 14V/
µ
s to reduce the electromag-
netic interference, but not for the enable transfer
characteristic (see fig. 1). An integrated active fly-
back voltage limitation clamps the output voltage
during the flyback phase of inductive loads to typ.
50V. The power DMOS switches ON, if the device
is enabled and the OUTput swings below ground.
This protection avoids the activation of parasitics
inside the power DMOS.
The DIAGnostic 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, discon-
nected 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 overtemperature.
DIAGNOSTIC TABLE
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)
HHHL (on)H(off)
L X X H (off) H(off)
Overtemperature,
disconnected ground or
supply voltage
H L X H (off) * H (off)
Overtemperature H H X H (off) * L (on)
X = not relevant * selective for each channel at overtemperature
L9338
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