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PDF LMD18201 Data sheet ( Hoja de datos )
| Número de pieza | LMD18201 | |
| Descripción | 3A / 55V H-Bridge | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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April 1998
LMD18201
3A, 55V H-Bridge
General Description
The LMD18201 is a 3A H-Bridge designed for motion control
applications. The device is built using a multi-technology pro-
cess which combines bipolar and CMOS control circuitry
with DMOS power devices on the same monolithic structure.
The H-Bridge configuration is ideal for driving DC and step-
per motors. The LMD18201 accommodates peak output cur-
rents up to 6A. Current sensing can be achieved via a small
sense resistor connected in series with the power ground
lead. For current sensing without disturbing the path of cur-
rent to the load, the LMD18200 is recommended.
Features
n Delivers up to 3A continuous output
n Operates at supply voltages up to 55V
n Low RDS(ON) typically 0.33Ω per switch
n TTL and CMOS compatible inputs
n No “shoot-through” current
n Thermal warning flag output at 145˚C
n Thermal shutdown (outputs off) at 170˚C
n Internal clamp diodes
n Shorted load protection
n Internal charge pump with external bootstrap capability
Applications
n DC and stepper motor drives
n Position and velocity servomechanisms
n Factory automation robots
n Numerically controlled machinery
n Computer printers and plotters
Functional Diagram
FIGURE 1. Functional Block Diagram of LMD18201
DS010793-1
© 1999 National Semiconductor Corporation DS010793
www.national.com
1 page  
Pinout Description
(See Connection Diagram)
Pin 1, BOOTSTRAP 1 Input: Bootstrap capacitor pin for half
H-Bridge number 1. The recommended capacitor (10 nF) is
connected between pins 1 and 2.
Pin 2, OUTPUT 1: Half H-Bridge number 1 output.
Pin 3, DIRECTION Input: See Table 1. This input controls
the direction of current flow between OUTPUT 1 and OUT-
PUT 2 (pins 2 and 10) and, therefore, the direction of rotation
of a motor load.
Pin 4, BRAKE Input: See Table 1. This input is used to
brake a motor by effectively shorting its terminals. When
braking is desired, this input is taken to a logic high level and
it is also necessary to apply logic high to PWM input, pin 5.
The drivers that short the motor are determined by the logic
level at the DIRECTION input (Pin 3): with Pin 3 logic high,
both current sourcing output transistors are ON; with Pin 3
logic low, both current sinking output transistors are ON. All
output transistors can be turned OFF by applying a logic high
to Pin 4 and a logic low to PWM input Pin 5; in this case only
a small bias current (approximately −1.5 mA) exists at each
output pin.
Pin 5, PWM Input: See Table 1. How this input (and DIREC-
TION input, Pin 3) is used is determined by the format of the
PWM Signal.
Pin 6, VS Power Supply
Pin 7, POWER GROUND/SENSE Connection: This pin is
the ground return for the power DMOS transistors of the
H-Bridge. The current through the H-Bridge can be sensed
by adding a small, 0.1Ω, sense resistor from this pin to the
power supply ground.
Pin 8, SIGNAL GROUND: This is the ground return for the
internal logic circuitry used to control the PWM switching of
the H-Bridge.
Pin 9, THERMAL FLAG Output: This pin provides the ther-
mal warning flag output signal. Pin 9 becomes active-low at
145˚C (junction temperature). However the chip will not shut
itself down until 170˚C is reached at the junction.
Pin 10, OUTPUT 2: Half H-Bridge number 2 output.
Pin 11, BOOTSTRAP 2 Input: Bootstrap capacitor pin for
half H-Bridge number 2. The recommended capacitor
(10 nF) is connected between pins 10 and 11.
PWM
H
H
L
H
H
L
TABLE 1. Logic Truth Table
Dir Brake Active Output Drivers
H L Source 1, Sink 2
L L Sink 1, Source 2
X L Source 1, Source 2
H H Source 1, Source 2
L H Sink 1, Sink 2
X H NONE
Application Information
TYPES OF PWM SIGNALS
The LMD18201 readily interfaces with different forms of
PWM signals. Use of the part with two of the more popular
forms of PWM is described in the following paragraphs.
Simple, locked anti-phase PWM consists of a single, vari-
able duty-cycle signal in which is encoded both direction and
amplitude information (see Figure 2). A 50% duty-cycle
PWM signal represents zero drive, since the net value of
voltage (integrated over one period) delivered to the load is
zero. For the LMD18201, the PWM signal drives the direc-
tion input (pin 3) and the PWM input (pin 5) is tied to logic
high.
DS010793-4
FIGURE 2. Locked Anti-Phase PWM Control
Sign/magnitude PWM consists of separate direction (sign)
and amplitude (magnitude) signals (see Figure 3). The (ab-
solute) magnitude signal is duty-cycle modulated, and the
absence of a pulse signal (a continuous logic low level) rep-
resents zero drive. Current delivered to the load is propor-
tional to pulse width. For the LMD18201, the DIRECTION in-
put (pin 3) is driven by the sign signal and the PWM input
(pin 5) is driven by the magnitude signal.
DS010793-5
FIGURE 3. Sign/Magnitude PWM Control
USING THE THERMAL WARNING FLAG
The THERMAL FLAG output (pin 9) is an open collector tran-
sistor. This permits a wired OR connection of thermal warn-
ing flag outputs from multiple LMD18201’s, and allows the
user to set the logic high level of the output signal swing to
match system requirements. This output typically drives the
interrupt input of a system controller. The interrupt service
routine would then be designed to take appropriate steps,
such as reducing load currents or initiating an orderly system
shutdown. The maximum voltage compliance on the flag pin
is 12V.
SUPPLY BYPASSING
During switching transitions the levels of fast current
changes experienced may cause troublesome voltage tran-
sients across system stray inductances.
It is normally necessary to bypass the supply rail with a high
quality capacitor(s) connected as close as possible to the VS
Power Supply (Pin 6) and POWER GROUND (Pin 7). A 1 µF
high-frequency ceramic capacitor is recommended. Care
should be taken to limit the transients on the supply pin be-
low the Absolute Maximum Rating of the device. When oper-
ating the chip at supply voltages above 40V a voltage sup-
pressor (transorb) such as P6KE62A is recommended from
5 www.national.com
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| PDF Descargar | [ Datasheet LMD18201.PDF ] | |
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