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LMD18400 Datasheet

Download or read online National Semiconductor LMD18400 Quad High Side Driver pdf datasheet.

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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 (
3 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
Separate ON OFF control of each switch is provided
through standard LSTLL CMOS logic compatible inputs
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
Typical Application
TRI-STATE is a registered trademark of National Semiconductor Corporation
is a trademark of National Semiconductor Corporation
C 1996 National Semiconductor Corporation
TL H 11026
Four independent outputs with
ous current capability
1 3
maximum ON resistance over temperature
True instantaneous power limit for each switch
High survival voltage (60 V
80V transient)
Shorted load (to ground and supply) protection
Overvoltage shutdown at V
CC l
LS TTL CMOS compatible logic inputs and outputs
10 A supply current in ‘‘sleep’’ mode
5V output clamp for discharging inductive loads
Serial data interface for 11 diagnostic checks
Switch ON OFF status
Open or shorted load
Operating temperature
Excessive supply voltage
Two direct-output error flags
Relay and solenoid drivers
High impedance automotive fuel injector drivers
Lamp drivers
Power supply switching
Motor drivers
Connection Diagram
Order Number LMD18400N
See NS Package Number N20A
TL H 11026 – 1
RRD-B30M76 Printed in U S A
June 1996
3A peak 1A continu-
TL H 11026 – 2
www national com

Summary of Contents

Page 1

... 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 ( 3 Amps transient common positive power sup- l ply The switches are fully protected from excessive voltage ...

Page 2

... Absolute Maximum Ratings If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Supply Survival Voltage (Pin 20) Transient (t 10 ms) e Continuous Output Transient Current (Each Switch) Output Transient Current (Total All Switches) Output Steady State Current (Each Switch) ...

Page 3

Electrical Characteristics over the entire operating temperature range Parameter AC CHARACTERISTICS Switch Turn-On Delay (t ) d(ON) Switch Turn-On Rise Time ( Switch Turn-Off Delay (t ) dOFF Switch Turn-Off Fall Time (t ) OFF Enable Time (t ...

Page 4

... Max A JA thermal shutdown For the LMD18400 the junction-to-ambient thermal resistance 2 c dissipation for the package will (Max Max Note 4 Typical values are and represent the most likely parametric norm ...

Page 5

Typical Performance Characteristics For all curves V 12V Temperature is the junction temperature unless otherwise noted e CC Switch ON Resistance vs Temperature TL H 1102631 Short Circuit Current vs Temperature TL H 1102634 Turn ON Rise Time vs Temperature ...

Page 6

Functional Block Diagram Truth Table Enable Chip Select Switch Control Input Input Input (Pin 3) (Pin 4) (Pins 12 ...

Page 7

... A The LMD18400 can be continually connected to a live pow- er source a car battery for example while drawing less than 10 A from the power source when put into a sleep con- dition This ‘ ...

Page 8

... FIGURE 3 Overvoltage Undervoltage Shutdown http www national com (Continued) The LMD18400 has been designed to drive all types of loads When driving a ground referenced inductive load such as a relay or solenoid the voltage across the load will reverse in polarity as the field in the inductor collapses when ...

Page 9

... The same principle of increasing output current as the volt- age across the load increases allows large capacitive loads to be charged more quickly by an LMD18400 driver than as opposed to a driver with a fixed 1A current limit protection scheme Figure 7 shows the output response while driving a ...

Page 10

... All of the diagnostic information is contained in an 11-bit word This data can be clocked out of the LMD18400 in a serial fashion as shown in Figure 8 The shift register is parallel loaded with the diagnostic data whenever the Chip Select Input is ...

Page 11

... 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 FIGURE 10 Detection Circuitry ...

Page 12

... Careful calculation of the worst case total power dissipation required at any point in time together with providing suffi- cient heatsinking will prevent this from occurring The LMD18400 is packaged with a special leadframe that helps dissipate heat through the two ground pins on each side of the package The thermal resistance from junction- ...

Page 13

Applications Information (Continued) FIGURE 13 Switching an Inductive Load When switched ON the worst case power dissipation where D(ON) Peak ON Peak The steady-state ON current of the inductor should be ...

Page 14

Applications ON OFF Switching of Multiple Voltage Regulated Circuit Loads http www national com Unipolar Drive for a 4-Phase Stepper Motor 11026 – 11026 26 ...

Page 15

... Recommended Connection if No Diagnostics are Required Simple protection of the LMD18400 against supply voltage reversal Loads will be energized through the intrinsic diodes in parallel with the power switches The Schottky diode will add approximately the logic input switching thresholds and the logic output low levels TL H 11026 – ...

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Applications (Continued) Parallelling switches for higher current capability Positive temperature coefficient of the switch ON resistance provides ballasting to evenly share the load current between the switches Any combination of switches can be paralleled Required peak load current will depend ...

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17 http www national com ...

Page 18

... Italiano National does not assume any responsibility for use of any circuitry described no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications Order Number LMD18400N NS Package Number N20A 2 A critical component is any component of a life ...

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