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PDF LMD18400 Data sheet ( Hoja de datos )
| Número de pieza | LMD18400 | |
| Descripción | Quad High Side Driver | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LMD18400 (archivo pdf) en la parte inferior de esta página. Total 18 Páginas | ||
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June 1996
LMD18400
Quad High Side Driver
General Description
The LMD18400 is a fully protected quad high side driver It
contains four common-drain DMOS N-channel power
switches each capable of switching a continuous 1 Amp
load (l3 Amps transient) to a common positive power sup-
ply The switches are fully protected from excessive voltage
current and temperature An instantaneous power sensing
circuit calculates the product of the voltage across and the
current through each DMOS switch and limits the power to a
safe level The device can be disabled to produce a ‘‘sleep’’
condition reducing the supply current to less than 10 mA
Separate ON OFF control of each switch is provided
through standard LSTLL CMOS logic compatible inputs
A MICROWIRETM compatible serial data interface is built in
to provide extensive diagnostic information This information
includes switch status readback output load fault conditions
and thermal and overvoltage shutdown status There are
also two direct-output error flags to provide an immediate
indication of a general system fault and an indication of ex-
cessive operating temperature
The LMD18400 is packaged in a special power dissipating
leadframe that reduces the junction to case thermal resist-
ance to approximately 20 C W
Features
Y Four independent outputs with l3A peak 1A continu-
ous current capability
Y 1 3X maximum ON resistance over temperature
Y True instantaneous power limit for each switch
Y High survival voltage (60 VDC 80V transient)
Y Shorted load (to ground and supply) protection
Y Overvoltage shutdown at VCC l 35V
Y LS TTL CMOS compatible logic inputs and outputs
Y k10 mA supply current in ‘‘sleep’’ mode
Y b5V output clamp for discharging inductive loads
Y Serial data interface for 11 diagnostic checks
Switch ON OFF status
Open or shorted load
Operating temperature
Excessive supply voltage
Y Two direct-output error flags
Applications
Y Relay and solenoid drivers
Y High impedance automotive fuel injector drivers
Y Lamp drivers
Y Power supply switching
Y Motor drivers
Typical Application
Connection Diagram
TRI-STATE is a registered trademark of National Semiconductor Corporation
MICROWIRETM is a trademark of National Semiconductor Corporation
C1996 National Semiconductor Corporation TL H 11026
TL H 11026 – 2
Order Number LMD18400N
See NS Package Number N20A
TL H 11026 – 1
RRD-B30M76 Printed in U S A
http www national com
1 page  
Typical Performance Characteristics
For all curves VCC e 12V Temperature is the junction temperature unless otherwise noted
Switch ON Resistance
vs Temperature
‘‘Sleep’’ Mode Supply Current
vs Temperature
Maximum Power
Dissipation vs
Ambient Temperature
TL H 11026–31
Short Circuit Current
vs Temperature
TL H 11026 – 32
Clamp Characteristics
vs Temperature
TL H 11026 – 33
Error Sense Threshold
Voltage vs Temperature
TL H 11026–34
Turn ON Rise Time
vs Temperature
TL H 11026 – 35
Turn ON Delay Time
vs Temperature
TL H 11026 – 36
Turn OFF Time
vs Temperature
TL H 11026–37
Switch Select Logic Input
Resistance vs Temperature
TL H 11026 – 38
Enable Threshold Voltage
vs Temperature
TL H 11026 – 39
Error Output Voltage
vs Sink Current
TL H 11026–40
TL H 11026 – 41
5
TL H 11026 – 42
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5 Page 
Applications Information (Continued)
The Error Flag output pin is an open drain transistor which
requires a pull-up resistor to a positive voltage of up to 16V
Typically this pull-up is to the same 5V supply which is bias-
ing the Enable input and any other external logic circuitry
The Error Flag pins of several LMD18400 packages can be
connected together with just one pull-up resistor to provide
an all-encompassing general system error indication Upon
detection of an error each device could then be polled for
diagnostic information to determine the source of the fault
condition
A second direct output error flag is for an indication of Ther-
mal Shutdown (pin 17) This active low flag provides an im-
mediate indication that the die temperature has reached
a170 C and that the drive to all four switches has been
removed This output is pulled up to the internal 5 1V logic
regulator through a small (5 mA) current source so use of a
buffer on this pin is recommended
TL H 11026 – 18
FIGURE 9 Thermal Shutdown Flag and Shutdown Input
A useful feature of pin 17 is that it can also be used as a
shutdown input Driving this pin low immediately switches all
of the drivers OFF just the same as if thermal shutdown
temperatures has been reached yet all of the control logic
and diagnostic circuits remain active This is useful in de-
signing ‘‘fail-safe’’ systems where the loads can be disabled
under any sort of externally detected system fault condition
The diagnostic logic however does not distinguish between
normal thermal shutdown or the fact that pin 17 has been
driven low As such various switch errors and an over-tem-
perature indication will be reported in the diagnostic data
stream
Figure 9 illustrates the use of pin 17 as both an output ther-
mal shutdown flag and as an input to shut down only the
switches Directly tying pin 17 to a5V will prevent the inter-
nal thermal shutdown circuitry from disabling the switches
For reliability purposes however this is not recommended as
there will then be no limit to the maximum die temperature
Refer to the Truth Table for a summary of the action of
these direct-output error flags
LOAD ERROR DETECTION
An important feature of the LMD18400 is the ability to de-
tect open or shorted load connections Figure 10 illustrates
the detection circuit used with each of the drivers
TL H 11026 – 19
FIGURE 10 Detection Circuitry
for Open Shorted Loads
A voltage comparator monitors the voltage to the load and
compares it to a fixed 4 1V reference level When a switch is
OFF the ground referenced load should have no voltage
across it Under this condition an internal 50 kX resistor
connected to VCC will provide a small amount of current to
the load If the load resistance is large enough to create a
voltage greater than 4 1V an Open Load Error will be indi-
cated for that switch The maximum load resistance that will
not generate an Open Load Error when a switch is OFF can
be found by
4 1V
RMax e VCC b 4 6V c 50 kX for no Open Load Indication
To make this Open Load Error threshold more sensitive an
external pull-up resistor can be added from the output to the
VCC supply
Also when a switch is commanded OFF should the load be
shorted to the VCC supply this same circuitry will again indi-
cate an error
When a switch is commanded ON the load is expected to
have a voltage across it that approaches the VCC potential
If the output voltage is less than the 4 1V threshold an error
will again be reported indicating that the load is either short-
ed to ground or that the driver is in power limit and not able
to pull the output voltage any closer to VCC The minimum
load resistance that will not generate a Shorted Load Error
when a switch is ON can be found by
RMin
e
4
1V
(VCC b
15W
4
1V)
for no Shorted Load Error
11 http www national com
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet LMD18400.PDF ] | |
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